Vibrio parahaemolyticus is the main cause of foodborne gastroenteritis,which is widely distributed in shellfish and other seafood.Most V.parahaemolyticus are nonpathogenic,and only a few types,such as serotype O3:K6,a...Vibrio parahaemolyticus is the main cause of foodborne gastroenteritis,which is widely distributed in shellfish and other seafood.Most V.parahaemolyticus are nonpathogenic,and only a few types,such as serotype O3:K6,are pathogenic,which is also the most prevalent strain in Asia.However,the relationship between this serotype and pathogenicity has yet to be established.The waaf gene is located in the O antigen synthesis gene cluster.Thus,we constructed a waaf gene deletion mutant(i.e.,Δwaaf)of wild-type(WT)which isolated from shellfish serotype O3:K6 via chitin-mediated transformation technology.We then constructed theΔwaaf complementary strain(i.e.,C-△waaf)via the Escherichia coli S17λpir strain by conjugation.The basic physiological characteristics,adhesion to Caco2 cells,and pathogenicity of the WT,△waaf,and C-△waaf strains were compared.Growth curves showed no remarkable differences between the WT andΔwaaf strains.However,theΔwaaf strain non-reactive to O3 antisera and other 12 O-group antisera of V.parahaemolyticus.Moreover,the number of flgella and extracellular polysaccharides decreased,the adhesion decreased,and the pathogenicity weakened.These characteristics of the C-△waaf strain were similar to those of the WT strain These results indicated that the waaf gene is vital to the serotype in V.parahaemolyticus,and changes in O antigen could affect the pathogenicity of this bacterium.This study will be helpful to understand the pathogenic mechanism of V.parahaemolyticus.展开更多
In order to determine the effect of foreign genes on a transgenic parasite,the pathogenicity and development in chickens of transgenic E.tenella strain TE1,which expresses yellow fluorescent protein (YFP) and dihydrof...In order to determine the effect of foreign genes on a transgenic parasite,the pathogenicity and development in chickens of transgenic E.tenella strain TE1,which expresses yellow fluorescent protein (YFP) and dihydrofolate reductase thymidylate synthase derived from Toxoplasma gondii(TgDHFR-TS), were compared with that of the parental strain BJ.Results indicated that the fecundity of the transgenic parasite(TE1) was reduced at least 4 times relative to that of the BJ strain.Low dosage of the TE1 strain induced less pathogenesis in chickens than did the BJ strain,but chickens inoculated with a higher dosage of TE1 oocysts displayed severe pathogenicity and mortality as did the BJ strain.In addition,trophozoites, the first generation and the second generation meronts and merozoites,microgamonts and macrogamonts of the transgenic parasite TE1 were seen by fluorescence microscopy.More interestingly,not all four sporonts in the sporulating transgenic oocysts express YFP.These findings suggest that the expression of YFP and TgDHFR-TS genes to some extent reduced pathogenicity and reproductive potential of transgenic E.tenella.Recombination between homologous or non-homologous chromosomes occurred during zygotic meiosis in E.tenella strain TE1.展开更多
Wilt disease with unknown etiology causes mass mortality in commercial Acacia mangium nurseries in South Sumatra.This pathogen induces symptoms of chlorosis in the lower leaves and develops into the shoots;subsequentl...Wilt disease with unknown etiology causes mass mortality in commercial Acacia mangium nurseries in South Sumatra.This pathogen induces symptoms of chlorosis in the lower leaves and develops into the shoots;subsequently,the plants wither and die.This research identifies the path-ogenic species causing this wilt disease and to assess its pathogenicity or virulence.Fifteen isolates of Fusarium oxysporum with varying colony sizes and color pigments were recovered from symptomatic A.mangium seedlings.The pathogenicity test showed that all isolates could infect plants with wilt severity reaching 80%,and the pathogen was verified as causing vascular disease.Koch’s postulate was verified by re-isolating the F.oxysporum isolates.The pathogen was confirmed by observing the morphological characters and elongation factor 1-α(tef1-α)gene sequences as F.oxysporum.展开更多
A novel technique for finding pathogenicity islands in genome data with independent component analyses(ICA) is present. First denoise the genomic signal sequences with ICA and detect G+C patterns in genomes by compari...A novel technique for finding pathogenicity islands in genome data with independent component analyses(ICA) is present. First denoise the genomic signal sequences with ICA and detect G+C patterns in genomes by comparing the result sequence with original sequences. The results on G+C patterns analysis of Dradiodurans chromosome I and N.serogroup A strain Z2491 are present. A set of loci that have very different G+C content and have not previously described are detected. The findings show that ICA is a powerful tool to detect differences within and between genomes and to separate small (gene level) and large (putative pathogenicity islands) genomic regions that have different composition characteristics.展开更多
The hazelnut weevil(Curculio dieckmanni Faust.)is a major pest of Asian hazel(Corylus heterophylla Fisch.)in China.Dead hazelnut weevil larvae were examined and the associated pathogenic bacterium was identifi ed as S...The hazelnut weevil(Curculio dieckmanni Faust.)is a major pest of Asian hazel(Corylus heterophylla Fisch.)in China.Dead hazelnut weevil larvae were examined and the associated pathogenic bacterium was identifi ed as Serratia marcescens Bizio.This signifi cantly shortened the lifespan of hazelnut weevil.Larval weight was reduced as a function of S.marcescens concentration and exposure time.The structure of infected midgut cells was altered,with necrosis of the wall tissues and many cells becoming dislodged,creating cavities.The S.marcencens strain inhibited digestive enzyme activity and protective enzymes in the midgut of adult hazelnut weevil.Inhibition on S.marcencens strain increased with treatment time.S.marcescens directly destroyed the midgut cells and interfered with digestive and protective enzymes.This decreased the food intake and increased mortality of hazelnut weevil.S.marcescens appears to be an eff ective bacterium for the control of hazelnut weevil but requires further study,including biological formulation development and fi eld application.展开更多
In our previous screening of the transcriptome of the causal agent of the devastating pine wilt disease,pine wood nematode(PWN,Bursaphelenchus xylophilus),after treatment with the nematicide fomepizole,Surfeit locus g...In our previous screening of the transcriptome of the causal agent of the devastating pine wilt disease,pine wood nematode(PWN,Bursaphelenchus xylophilus),after treatment with the nematicide fomepizole,Surfeit locus gene sft-4,which encodes a regulatory factor,was found to be downregulated.In situ hybridization results showed that the sft-4 was continuously expressed from egg to adult and was especially high in the reproductive system.Here in a study of the effect of RNA interference(RNAi)of sft-4 and recombinant SFT-4 on PWN activity,treatment with sft-4 dsRNA inhibited feeding,reproduction,oviposition and egg hatching of PWN with the greatest inhibition on reproduction and oviposition,whereas recombinant SFT-4 had the opposite effect.In addition,RNAi of sft-4 changed the female–male ratio and lifespan of PWN.In bioassays of PWNs,with RNAi of sft-4 on seedlings and 2-year-old Pinus thunbergii trees,none of the treated plants developed symp-toms during the monitoring period,indicating that virulence of PWNs was either significantly weakened.These results indicate that the influence of sft-4 on PWN pathogenicity may be mainly through regulating reproductive function of PWN and its lifespan.展开更多
In this study,the hydrothermal method was employed to grow submicron CuS on carbon cloth(CC),and the photoreduction method was used to grow Ag nanoparticles on the CuS submicron flowers,thus forming the Ag/CuS/CC cata...In this study,the hydrothermal method was employed to grow submicron CuS on carbon cloth(CC),and the photoreduction method was used to grow Ag nanoparticles on the CuS submicron flowers,thus forming the Ag/CuS/CC catalytic electrode.The application of Ag/CuS/CC electrode-coupled dielectric barrier discharge(DBD)plasma in the disinfection of pathogenic bacteria in water was studied.The Ag/CuS/CC electrode exhibits strong antibacterial activity,and under an external voltage of 30 V,the degradation efficiency of Bacillus subtilis reaches 99.99%within 15 min without regeneration.After five cycles,the inactivation rate of Bacillus subtilis reached 99.99%within 25 min.The practical applicability of the Ag/CuS/CC-coupled DBD system for treating actual wastewater was evaluated,and the changes in biological toxicity were investigated.The results indicate that the prepared Ag/CuS/CC coupled DBD has great potential for safe disinfection of pathogenic bacteria in water through integrated processes.展开更多
This paper concentrates on the dynamics of a waterborne pathogen periodic PDE model with environmental pollution.For this model,we derive the basic reproduction number R0and establish a threshold type result on its gl...This paper concentrates on the dynamics of a waterborne pathogen periodic PDE model with environmental pollution.For this model,we derive the basic reproduction number R0and establish a threshold type result on its global dynamics in terms of R0,which predicts the extinction or persistence of diseases.More precisely,the disease-free steady state is globally attractive if R_(0)<1,while the system admits at least one positive periodic solution and the disease is uniformly persistent if R_(0)>1.Moreover,we carry out some numerical simulations to illustrate the long-term behaviors of solutions and explore the influence of environmental pollution and seasonality on the spread of waterborne diseases.展开更多
Pine wilt disease(PWD)is one of the most devastating diseases of Pinu s spp.and is caused by the pine wood nematode(PWN),Bursaphelenchus xylophilus(Steiner&Buhrer)Nickle.To study adaptation of PWN to survive in ho...Pine wilt disease(PWD)is one of the most devastating diseases of Pinu s spp.and is caused by the pine wood nematode(PWN),Bursaphelenchus xylophilus(Steiner&Buhrer)Nickle.To study adaptation of PWN to survive in hosts that differ in resistance,we examined the self-regulatory characteristics of PWN at the biological and molecular levels early in the interaction.Two-year-old susceptible Pinus thunbergii and resistant Pinus taeda were selected for this experiment,and changes in PWNs after inoculation were assessed.q RT-PCR was used to detect changes in genes related to PWN pathogenicity and detoxification.The results showed that the migration and reproductive abilities of PWNs in P.thunbergii were stronger than those of PWNs in P.taeda.After 7 d,the number of nematodes in P.thunbergii was approximately 3.2-fold higher than in P.taeda.After 15 d,the number of nematodes in P.thunbergii was approximately twofold higher than that in P.taeda.Because PWN can adjust its sex ratio after infection,we compared the sex ratio of uninoculated PWNs,to that in the two pine species.In P.thunbergii,the female to male ratio first decreased and then stabilized over time;in P.taeda first decreased and then increased.Relative fat accumulation in PWNs increased significantly after the PWNs entered the tree body;the accumulation rate in P.thunbergii was higher than in P.taeda at 7 d,but lower after 15 d.Scanning electron microscopy(SEM)showed significantly more bacteria on the surface of PWNs in P.taeda compared with PWNs in susceptible P.thunbergii.At 12 h after inoculation,the expression of genes related to cell-wall degradation(Bx Beta1-4 and Bxpel1),effectors(Bx CDP1,Bx Sap B1),and active oxygen metabolism(Bxy-ctl-1 and Bx GST3)was 2–6×higher in the resistant pine than in the susceptible one.In contrast,in PWNs,the expression of autophagy-related genes Bx ATG1 and Bx ATG16 was 1.5–2 times higher in P.thunbergii than in P.taeda.These results indicate that the interaction between PWNs and pine trees with different resistance levels elicits a series of physiological and molecular adaptations that affect nematode reproduction and virulence.This study will help elucidate the adaptive mechanisms of PWN in different pine trees.展开更多
Ophiostomatalean fungi may facilitate bark beetle colonization and reproduction.In the present study of the fungal community associated with bark beetle species belonging to Tomicus in Yunnan,China,six ophiostomatalea...Ophiostomatalean fungi may facilitate bark beetle colonization and reproduction.In the present study of the fungal community associated with bark beetle species belonging to Tomicus in Yunnan,China,six ophiostomatalean fungi(Ophiostoma canum,O.ips,O.tingens,Leptographium yunnanense,Leptographium sp.1 and Leptographium sp.2)were isolated from the beetles or their galleries;O.canum was the most common fungal species.The distribution of O.canum was associated with stands heavily damaged by Tomicus species and a higher percentage of valid galleries of Tomicus yunnanensis and T.minor in Yunnan pine(Pinus yunnanensis).After inoculation of Yunnan pine with the fungus,a phloem reaction zone formed and monoterpenes accumulated in the phloem.These results suggested that O.canum was pathogenic to Yunnan pine and that the wide distribution of the fungus might be benefi cial to reproduction of pine shoot beetles in Yunnan pine.However,because the reaction zone and monoterpene accumulation were mild,fungal damage of Yunnan pine might be limited.A more integrated study considering all the fungal species should be done to better understand the interactions among bark beetles,blue-stain fungi,and the tree hosts in the region.展开更多
Boxelder maple(Acer negundo L.)is widely grown as ornamental trees in China.In 2017 in Pizhou,Jiangsu Province,China,the boxelder maple trees suffered from a disease which caused wilting and yellowing leaves,rotted ro...Boxelder maple(Acer negundo L.)is widely grown as ornamental trees in China.In 2017 in Pizhou,Jiangsu Province,China,the boxelder maple trees suffered from a disease which caused wilting and yellowing leaves,rotted roots,and discolored xylem.The disease broke out from July to August.Seven fungal isolates were obtained from symptomatic tissue and tested for pathogenicity.Isolate An7 was isolated at high frequency from the discolored vascular tissues,which caused the wilt disease on healthy 2-year-old seedlings after inoculation and eventually killed all the seedlings.We conducted molecular analysis for An7,including the partial sequences of the rDNA internal transcribed spacer,calmodulin,RNA polymerase II second largest subunit and the translation elongation factor 1-αand evaluation of the variously sized conidia,chlamydospores and conidiophores and cultural traits.The pathogen was identified as Fusarium nirenbergiae,a member of the Fusarium oxysporum species complex.To our knowledge,this is the first report of F.nirenbergiae causing wilt on A.negundo in China.展开更多
Numerous Trichoderma spp. are mycoparasites and commercially applied as biological control agents against a large number of plant pathogenic fungi. The mycoparasitic interaction is host-specific and several research s...Numerous Trichoderma spp. are mycoparasites and commercially applied as biological control agents against a large number of plant pathogenic fungi. The mycoparasitic interaction is host-specific and several research strategies have been applied to identify the main genes and compounds involved in the antagonist-plant-pathogen three-way interaction. During mycoparasitism, signals from the host fungus are recognised by Trichoderma, stimulating antifungal activities that are accompanied by morphological changes and the secretion of hydrolytic enzymes and antibiotics. Interestingly some morphological changes appeared highly conserved in the strategy of pathogenicity within the fungal world, i.e. the formation of appressoria as well as the secretion of hydrolytic enzymes seem to be general mechanisms of attack both for plant pathogens and mycoparasitic antagonists. This knowledge is being used to identify receptors and key components of signalling pathways involved in fungus-fungus interaction. For this purpose we have cloned the first genes (tmk1, tga1, tga3) from T. atroviride showing a high similarity to MAP kinase and G protein subunits (see abstract by Zeilinger et al.), which have been found to have an important role in pathogenicity by Magnaporthe grisea. To identify the function and involvement of these factors in mycoparasitism by T. atroviride, tmk1, tga1, tga3 disruptant strains were produced. The knock-out mutants were tested by in vivo biocontrol assays for their ability to inhibit soil and foliar plant pathogens such as Rhizoctonia solani, Pythium ultimum and Botrytis cinerea . Disruption of these genes corresponded to a complete loss of biocontrol ability, suggesting a significant role in mycoparasitism. In particular, it has been suggested that tga3 regulates the expression of chitinase-encoding genes, the secretion of the corresponding enzymes and the process of conidiation. Comparative proteome analysis of wild type and disruptants supported this hypothesis, and indicated many changes in the protein profiles of T. atroviride in different interaction conditions with plants and pathogenic hosts.展开更多
The poplar and willow weevil,Crypto rhynchus lapathi L.,a major universally destructive wood-boring insect has become one of the important quarantine pests that is extremely destructive to forestry development and nee...The poplar and willow weevil,Crypto rhynchus lapathi L.,a major universally destructive wood-boring insect has become one of the important quarantine pests that is extremely destructive to forestry development and needs to be controlled.Entomopathogenic fungi(EPF) are considered safe and friendly for humans and the environment and play important roles in controlling insect pest populations.In this study,the screening of entomopathogenic fungi for control of C.lapathi is reported through the evaluation of virulence of four fungal Beauveria bassiana(CFCC81428,CFCC83116,CFCC83486,CFCC87297)strains,one B.brongniartii(CFCC83487) strain and one Metarhizium anisopliae(CFCC88953) strain.The virulence of the different strains was appraised by correct mortality rate,cumulative mortality rate,median lethal concentration(LC_(50)) and median lethal time(LT_(50)).B.bassiana strains CFCC81428 and CFCC83116 were the most virulent among the six strains with a mortality up to 100%,and the LT_(50) were 2.7 and 3.1 days.Five conidia concentrations of three strains(CFCC81428,CFCC83116 and CFCC87298) that caused high virulence was screened for dose-relationship.Their effect on controlling C.lapathi larvae were also determined under field condition by brushing conidia suspensions on C.lapathi larvae infested in a poplar trunk.The cumulative rate in the field was lower than those obtained from the laboratory,but the order of the virulence of different strains did not change.Mortality in all three strains occurred at their highest concentration(1.0 × 10^(8) conidia mL^(-1)).Under field conditions,the CFCC81428 strain was the most effective,causing mortalities of 80.3% and 75.2%in two plots in Beipiao and Lindian counties,respectively,followed by CFCC83116(69.1%,66.6%) and CFCC87298(60.7%,59.3%).Based on our results,the B.bassiana strain CFCC81428 has the potential as a biological insecticide to control C.lapathi larvae.展开更多
The objective of this study was to construct the infectious clone of encephalomyocarditis virus (EMCV) BJC3 strain.The genomic cDNA of the virus was amplified by three overlapping segments using RT-PCR,and cloned into...The objective of this study was to construct the infectious clone of encephalomyocarditis virus (EMCV) BJC3 strain.The genomic cDNA of the virus was amplified by three overlapping segments using RT-PCR,and cloned into low-copy plasmid pWSK29 to construct the full-length cDNA clone pWSKBJC3/ w.The pWSKBJC3/w was in vitro transcribed and transfected into BHK-21 cells to rescue the virus.The results showed that the full-length cDNA clone was infectious and the virus could be rescued in BHK-21 cells.The rescued virus designated RvBJC3W was identified by RT-PCR and indirect immunofluorescence assay(IFA).The rescued virus had similar growth characteristics to its parental virus BJC3 and retained pathogenicity for mice.Our results indicate that the first infectious cDNA clone of EMCV in China has been successfully established and provides an essential tool for investigating the molecular basis of pathogenicity of EMCV.展开更多
BACKGROUND： With mechanical ventilation widely used in intensive care unit, the ventilator associated pneumonia （VAP） has become a common and serious complication in critically ill patients. Compared with adults, t...BACKGROUND： With mechanical ventilation widely used in intensive care unit, the ventilator associated pneumonia （VAP） has become a common and serious complication in critically ill patients. Compared with adults, the incidence of VAP and the mortality are higher in children in pediatric intensive care unit （PICU） because of immune deficiency, severe basic diseases, and increased use of artificial airway or mechanical ventilation. Hence it is of significance to study the epidemiology and changes of antibacterial susceptibility in order to reduce the incidence and mortality of VAP in children.METHODS： From January 2008 to June 2010, 2758 children were treated in PICU of Wuhan Children＇s Hospital. Among them, 171 received mechanical ventilation over 48 hours in PICU, and 46 developed VAP. The distribution and drug-resistance pattern of the pathogenic bacteria isolated from lower respiratory tract aspirations were analyzed. RESULTS：A total of 119 pathogenic microbial strains were isolated. Gram-negative bacilli （G-） were the most （65.55%）, followed by fungi （21.01%） and gram-positive cocci （G~, 13.45%）. Among them, the most common pathogens were Acinetobacter baummannii, Escherichia coli, Klebsiella pneumoniae, candida albicans and coagulase-negative staphylococci. Antibiotic susceptibility tests indicated that the multiple drug-resistances of G- and G＋to antibiotics were serious. Most of G- was sensitive to ciprofloxacin, amikacin, imipenem, meropenem, cefoperazone-sulbactam and piperacillin-tazobactam. The susceptibility of G＋ to vancomycin, teicoplanin and linezolid were 100%. Fungi were almost sensitive to all the antifungal agents. The primary pathogens of VAP were G-, and their multiple drug-resistances were serious. CONCLUSION： In clinical practice we should choose the most sensitive drug for VAP according to pathogenic test.展开更多
Listeria monocytogenes is an important foodborne pathogen responsible for listeriosis,a fatal disease.It is widely distributed in various foods and environmental sources.In this review,we focused on addressing PCR-bas...Listeria monocytogenes is an important foodborne pathogen responsible for listeriosis,a fatal disease.It is widely distributed in various foods and environmental sources.In this review,we focused on addressing PCR-based technologies,including conventional PCR,qPCR and droplet digital PCR(ddPCR).Specifically,we described(a)conventional PCR and mono-,duplex-and multiplex-qPCR methodologies;(b)development and applications of gene HlyA-,Iap-,PrfA–and SsrA-based conventional and qPCR assays as well as PCR assays targeting newly identified gene targets for specific detection of L.monocytogenes;differentiation of viable from dead L.monocytogenes by qPCR in conjugation with propidium monoazide pretreatment;PCR-based serotype identification of L.monocytogenes isolates;PCR-based detection of L.ivanovii,infecting ruminants,differentiation of L.monocytogenes from other Listeria species;and sigB-gene based PCR identification of Listeria spp;(c)applications of ddPCR in detection of L.monocytogenes;and(d)application of qPCR assays in detection and subtyping of L.monocytogenes in milk and dairy products;meats,meat products and meat-processing environment;and seafood,seafood products and processing environment.Our goal was to provide a relatively comprehensive overview of PCR-based methodologies available in detection,characterization and subtyping of various strains of L.monocytogenes in foods and environmental sources.展开更多
DNA was extracted from the strain of pathogen of poplar leaf blight using a modified CTAB method. ITS sequence （601bp） was initially amplified from the pathogen by using the universal primers ITSl and ITS4 （registe...DNA was extracted from the strain of pathogen of poplar leaf blight using a modified CTAB method. ITS sequence （601bp） was initially amplified from the pathogen by using the universal primers ITSl and ITS4 （registered No, DQ011257）. Comparing to the nucleotide sequences acquired from GenBank database, the strain is clustered into the homogeneity with Alternaria alternate （AY787684） and Alternaria alternate （AY354228）, with a homology of 98%, thus the strain was checked as Alternaria alternata （Fr.） Keissler. The optimal conditions for conidia germination and mycelium growth of the pathogen were tested, The optimal temperature for conidia germinating and mycelium growth is 25℃, and the optimal pH value is 6. Mycelium grows rather slowly at 10℃ and 30℃ and growth stops at above 35 ℃. Among the six culture mediums tested, PDA ＋ poplar leaf juice medium is most favorable for mycelium growth.展开更多
Chinese hackberry(Celtis sinensis Pers.)is an adaptable species widely growing in southern China.The symptoms of canker on stems of seedlings were discovered mid-July 2017 in Shuyang,Jiangsu Province.The diseased port...Chinese hackberry(Celtis sinensis Pers.)is an adaptable species widely growing in southern China.The symptoms of canker on stems of seedlings were discovered mid-July 2017 in Shuyang,Jiangsu Province.The diseased portions of the stems were dark brown due to discoloured xylem.Some seedlings showed symptoms of wilting,leaf fall,twig dieback,and tissue discolouration.The outbreak period was concentrated in July and August,suggesting that the disease spread during summer months.Possible fungal causal agents were isolated from naturally infected canker tissue and discoloured xylem.The isolate from xylem tissue with a high frequency(>50%)was named Ls7 type.Pathogenicity tests were carried out on 4-yearold seedlings.The symptoms of canker began to develop 20 days after inoculation with Ls7 isolate and by day 35,there were dark,enlarged longitudinal lesions.A phylogenetic tree of the isolate was developed using the internal transcribed spacer,elongation factor-1α(tef1-α),β-tubulin gene(TUB)and RNA polymerase II subunit primer genes(RPB2).Based on morphological features and phylogenetic information,the pathogen was identifi ed as Lasiodiplodia pseudotheobromae.This is the fi rst report of L.pseudotheobromae causing canker on Chinese hackberry stems in China.展开更多
基金supported by grants from the Natural Science Foundation of Chongqing(cstc2020jcyj-msxm X0685)the Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN202001231)+1 种基金the National Natural Science Foundation of China(NSFC)(No.31201372)Science and Technology Project of Wanzhou in 2020。
文摘Vibrio parahaemolyticus is the main cause of foodborne gastroenteritis,which is widely distributed in shellfish and other seafood.Most V.parahaemolyticus are nonpathogenic,and only a few types,such as serotype O3:K6,are pathogenic,which is also the most prevalent strain in Asia.However,the relationship between this serotype and pathogenicity has yet to be established.The waaf gene is located in the O antigen synthesis gene cluster.Thus,we constructed a waaf gene deletion mutant(i.e.,Δwaaf)of wild-type(WT)which isolated from shellfish serotype O3:K6 via chitin-mediated transformation technology.We then constructed theΔwaaf complementary strain(i.e.,C-△waaf)via the Escherichia coli S17λpir strain by conjugation.The basic physiological characteristics,adhesion to Caco2 cells,and pathogenicity of the WT,△waaf,and C-△waaf strains were compared.Growth curves showed no remarkable differences between the WT andΔwaaf strains.However,theΔwaaf strain non-reactive to O3 antisera and other 12 O-group antisera of V.parahaemolyticus.Moreover,the number of flgella and extracellular polysaccharides decreased,the adhesion decreased,and the pathogenicity weakened.These characteristics of the C-△waaf strain were similar to those of the WT strain These results indicated that the waaf gene is vital to the serotype in V.parahaemolyticus,and changes in O antigen could affect the pathogenicity of this bacterium.This study will be helpful to understand the pathogenic mechanism of V.parahaemolyticus.
基金supported by the National High Technology Research and Development Program of China(Project No. 2006AA02Z458)the Doctor Startup Foundation of Henan University of Science and Technology(09001350)
文摘In order to determine the effect of foreign genes on a transgenic parasite,the pathogenicity and development in chickens of transgenic E.tenella strain TE1,which expresses yellow fluorescent protein (YFP) and dihydrofolate reductase thymidylate synthase derived from Toxoplasma gondii(TgDHFR-TS), were compared with that of the parental strain BJ.Results indicated that the fecundity of the transgenic parasite(TE1) was reduced at least 4 times relative to that of the BJ strain.Low dosage of the TE1 strain induced less pathogenesis in chickens than did the BJ strain,but chickens inoculated with a higher dosage of TE1 oocysts displayed severe pathogenicity and mortality as did the BJ strain.In addition,trophozoites, the first generation and the second generation meronts and merozoites,microgamonts and macrogamonts of the transgenic parasite TE1 were seen by fluorescence microscopy.More interestingly,not all four sporonts in the sporulating transgenic oocysts express YFP.These findings suggest that the expression of YFP and TgDHFR-TS genes to some extent reduced pathogenicity and reproductive potential of transgenic E.tenella.Recombination between homologous or non-homologous chromosomes occurred during zygotic meiosis in E.tenella strain TE1.
基金The work was supported by the Directorate General of Research and Development,Ministry of Research,Technology and Higher Education through the PMDSU scholarship 2020−2021 according to the Director of Research and Community Service,Directorate of Research and Community Service,chaired by Ahmad Muslim number 0124/UN9/SB3.LP2M.PT/2020.
文摘Wilt disease with unknown etiology causes mass mortality in commercial Acacia mangium nurseries in South Sumatra.This pathogen induces symptoms of chlorosis in the lower leaves and develops into the shoots;subsequently,the plants wither and die.This research identifies the path-ogenic species causing this wilt disease and to assess its pathogenicity or virulence.Fifteen isolates of Fusarium oxysporum with varying colony sizes and color pigments were recovered from symptomatic A.mangium seedlings.The pathogenicity test showed that all isolates could infect plants with wilt severity reaching 80%,and the pathogen was verified as causing vascular disease.Koch’s postulate was verified by re-isolating the F.oxysporum isolates.The pathogen was confirmed by observing the morphological characters and elongation factor 1-α(tef1-α)gene sequences as F.oxysporum.
基金Supported by the Electronic Science Foundation of China (No.51415010101DZ02)
文摘A novel technique for finding pathogenicity islands in genome data with independent component analyses(ICA) is present. First denoise the genomic signal sequences with ICA and detect G+C patterns in genomes by comparing the result sequence with original sequences. The results on G+C patterns analysis of Dradiodurans chromosome I and N.serogroup A strain Z2491 are present. A set of loci that have very different G+C content and have not previously described are detected. The findings show that ICA is a powerful tool to detect differences within and between genomes and to separate small (gene level) and large (putative pathogenicity islands) genomic regions that have different composition characteristics.
基金the National Key Research and Development project of China(2016YFC0500308)Special Project for Double First-Class-Cultivation of Innovative Talents(000/41113102)+1 种基金the Natural Science Foundation of Heilongjiang Scientifi c Committee(C2018055)the Application Research Project of Heilongjiang Provincial Forest Industry Administration(sgzjY2014004).
文摘The hazelnut weevil(Curculio dieckmanni Faust.)is a major pest of Asian hazel(Corylus heterophylla Fisch.)in China.Dead hazelnut weevil larvae were examined and the associated pathogenic bacterium was identifi ed as Serratia marcescens Bizio.This signifi cantly shortened the lifespan of hazelnut weevil.Larval weight was reduced as a function of S.marcescens concentration and exposure time.The structure of infected midgut cells was altered,with necrosis of the wall tissues and many cells becoming dislodged,creating cavities.The S.marcencens strain inhibited digestive enzyme activity and protective enzymes in the midgut of adult hazelnut weevil.Inhibition on S.marcencens strain increased with treatment time.S.marcescens directly destroyed the midgut cells and interfered with digestive and protective enzymes.This decreased the food intake and increased mortality of hazelnut weevil.S.marcescens appears to be an eff ective bacterium for the control of hazelnut weevil but requires further study,including biological formulation development and fi eld application.
基金supported by the Shandong Provincial Natural Science Foundation,China(ZR2020MC123)Qingdao Municipal People-benefitting Demonstration Project of Science and Technology,China(23-2-8-cspz-8-nsh).
文摘In our previous screening of the transcriptome of the causal agent of the devastating pine wilt disease,pine wood nematode(PWN,Bursaphelenchus xylophilus),after treatment with the nematicide fomepizole,Surfeit locus gene sft-4,which encodes a regulatory factor,was found to be downregulated.In situ hybridization results showed that the sft-4 was continuously expressed from egg to adult and was especially high in the reproductive system.Here in a study of the effect of RNA interference(RNAi)of sft-4 and recombinant SFT-4 on PWN activity,treatment with sft-4 dsRNA inhibited feeding,reproduction,oviposition and egg hatching of PWN with the greatest inhibition on reproduction and oviposition,whereas recombinant SFT-4 had the opposite effect.In addition,RNAi of sft-4 changed the female–male ratio and lifespan of PWN.In bioassays of PWNs,with RNAi of sft-4 on seedlings and 2-year-old Pinus thunbergii trees,none of the treated plants developed symp-toms during the monitoring period,indicating that virulence of PWNs was either significantly weakened.These results indicate that the influence of sft-4 on PWN pathogenicity may be mainly through regulating reproductive function of PWN and its lifespan.
基金funded by the National College Student Innovation and Entrepreneurship Training Program(No.GJ202323011)。
文摘In this study,the hydrothermal method was employed to grow submicron CuS on carbon cloth(CC),and the photoreduction method was used to grow Ag nanoparticles on the CuS submicron flowers,thus forming the Ag/CuS/CC catalytic electrode.The application of Ag/CuS/CC electrode-coupled dielectric barrier discharge(DBD)plasma in the disinfection of pathogenic bacteria in water was studied.The Ag/CuS/CC electrode exhibits strong antibacterial activity,and under an external voltage of 30 V,the degradation efficiency of Bacillus subtilis reaches 99.99%within 15 min without regeneration.After five cycles,the inactivation rate of Bacillus subtilis reached 99.99%within 25 min.The practical applicability of the Ag/CuS/CC-coupled DBD system for treating actual wastewater was evaluated,and the changes in biological toxicity were investigated.The results indicate that the prepared Ag/CuS/CC coupled DBD has great potential for safe disinfection of pathogenic bacteria in water through integrated processes.
基金supported by the NSFC(12161079)the XSTP(KC2023058)。
文摘This paper concentrates on the dynamics of a waterborne pathogen periodic PDE model with environmental pollution.For this model,we derive the basic reproduction number R0and establish a threshold type result on its global dynamics in terms of R0,which predicts the extinction or persistence of diseases.More precisely,the disease-free steady state is globally attractive if R_(0)<1,while the system admits at least one positive periodic solution and the disease is uniformly persistent if R_(0)>1.Moreover,we carry out some numerical simulations to illustrate the long-term behaviors of solutions and explore the influence of environmental pollution and seasonality on the spread of waterborne diseases.
基金supported by the major emergency project in science and technology of National Forestry and Grassland Administration(ZD202001)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘Pine wilt disease(PWD)is one of the most devastating diseases of Pinu s spp.and is caused by the pine wood nematode(PWN),Bursaphelenchus xylophilus(Steiner&Buhrer)Nickle.To study adaptation of PWN to survive in hosts that differ in resistance,we examined the self-regulatory characteristics of PWN at the biological and molecular levels early in the interaction.Two-year-old susceptible Pinus thunbergii and resistant Pinus taeda were selected for this experiment,and changes in PWNs after inoculation were assessed.q RT-PCR was used to detect changes in genes related to PWN pathogenicity and detoxification.The results showed that the migration and reproductive abilities of PWNs in P.thunbergii were stronger than those of PWNs in P.taeda.After 7 d,the number of nematodes in P.thunbergii was approximately 3.2-fold higher than in P.taeda.After 15 d,the number of nematodes in P.thunbergii was approximately twofold higher than that in P.taeda.Because PWN can adjust its sex ratio after infection,we compared the sex ratio of uninoculated PWNs,to that in the two pine species.In P.thunbergii,the female to male ratio first decreased and then stabilized over time;in P.taeda first decreased and then increased.Relative fat accumulation in PWNs increased significantly after the PWNs entered the tree body;the accumulation rate in P.thunbergii was higher than in P.taeda at 7 d,but lower after 15 d.Scanning electron microscopy(SEM)showed significantly more bacteria on the surface of PWNs in P.taeda compared with PWNs in susceptible P.thunbergii.At 12 h after inoculation,the expression of genes related to cell-wall degradation(Bx Beta1-4 and Bxpel1),effectors(Bx CDP1,Bx Sap B1),and active oxygen metabolism(Bxy-ctl-1 and Bx GST3)was 2–6×higher in the resistant pine than in the susceptible one.In contrast,in PWNs,the expression of autophagy-related genes Bx ATG1 and Bx ATG16 was 1.5–2 times higher in P.thunbergii than in P.taeda.These results indicate that the interaction between PWNs and pine trees with different resistance levels elicits a series of physiological and molecular adaptations that affect nematode reproduction and virulence.This study will help elucidate the adaptive mechanisms of PWN in different pine trees.
文摘Ophiostomatalean fungi may facilitate bark beetle colonization and reproduction.In the present study of the fungal community associated with bark beetle species belonging to Tomicus in Yunnan,China,six ophiostomatalean fungi(Ophiostoma canum,O.ips,O.tingens,Leptographium yunnanense,Leptographium sp.1 and Leptographium sp.2)were isolated from the beetles or their galleries;O.canum was the most common fungal species.The distribution of O.canum was associated with stands heavily damaged by Tomicus species and a higher percentage of valid galleries of Tomicus yunnanensis and T.minor in Yunnan pine(Pinus yunnanensis).After inoculation of Yunnan pine with the fungus,a phloem reaction zone formed and monoterpenes accumulated in the phloem.These results suggested that O.canum was pathogenic to Yunnan pine and that the wide distribution of the fungus might be benefi cial to reproduction of pine shoot beetles in Yunnan pine.However,because the reaction zone and monoterpene accumulation were mild,fungal damage of Yunnan pine might be limited.A more integrated study considering all the fungal species should be done to better understand the interactions among bark beetles,blue-stain fungi,and the tree hosts in the region.
基金The work was supported by the National Key Research and Development Program of China(Grant Number:2017YFD0600104).
文摘Boxelder maple(Acer negundo L.)is widely grown as ornamental trees in China.In 2017 in Pizhou,Jiangsu Province,China,the boxelder maple trees suffered from a disease which caused wilting and yellowing leaves,rotted roots,and discolored xylem.The disease broke out from July to August.Seven fungal isolates were obtained from symptomatic tissue and tested for pathogenicity.Isolate An7 was isolated at high frequency from the discolored vascular tissues,which caused the wilt disease on healthy 2-year-old seedlings after inoculation and eventually killed all the seedlings.We conducted molecular analysis for An7,including the partial sequences of the rDNA internal transcribed spacer,calmodulin,RNA polymerase II second largest subunit and the translation elongation factor 1-αand evaluation of the variously sized conidia,chlamydospores and conidiophores and cultural traits.The pathogen was identified as Fusarium nirenbergiae,a member of the Fusarium oxysporum species complex.To our knowledge,this is the first report of F.nirenbergiae causing wilt on A.negundo in China.
文摘Numerous Trichoderma spp. are mycoparasites and commercially applied as biological control agents against a large number of plant pathogenic fungi. The mycoparasitic interaction is host-specific and several research strategies have been applied to identify the main genes and compounds involved in the antagonist-plant-pathogen three-way interaction. During mycoparasitism, signals from the host fungus are recognised by Trichoderma, stimulating antifungal activities that are accompanied by morphological changes and the secretion of hydrolytic enzymes and antibiotics. Interestingly some morphological changes appeared highly conserved in the strategy of pathogenicity within the fungal world, i.e. the formation of appressoria as well as the secretion of hydrolytic enzymes seem to be general mechanisms of attack both for plant pathogens and mycoparasitic antagonists. This knowledge is being used to identify receptors and key components of signalling pathways involved in fungus-fungus interaction. For this purpose we have cloned the first genes (tmk1, tga1, tga3) from T. atroviride showing a high similarity to MAP kinase and G protein subunits (see abstract by Zeilinger et al.), which have been found to have an important role in pathogenicity by Magnaporthe grisea. To identify the function and involvement of these factors in mycoparasitism by T. atroviride, tmk1, tga1, tga3 disruptant strains were produced. The knock-out mutants were tested by in vivo biocontrol assays for their ability to inhibit soil and foliar plant pathogens such as Rhizoctonia solani, Pythium ultimum and Botrytis cinerea . Disruption of these genes corresponded to a complete loss of biocontrol ability, suggesting a significant role in mycoparasitism. In particular, it has been suggested that tga3 regulates the expression of chitinase-encoding genes, the secretion of the corresponding enzymes and the process of conidiation. Comparative proteome analysis of wild type and disruptants supported this hypothesis, and indicated many changes in the protein profiles of T. atroviride in different interaction conditions with plants and pathogenic hosts.
基金The work was supported by the“Applied Technology Research and Development Project of Heilongjiang Province(GA20B401-2)”the Central University Basic Research Business Expenses Special Fund Project(2572018BA06).
文摘The poplar and willow weevil,Crypto rhynchus lapathi L.,a major universally destructive wood-boring insect has become one of the important quarantine pests that is extremely destructive to forestry development and needs to be controlled.Entomopathogenic fungi(EPF) are considered safe and friendly for humans and the environment and play important roles in controlling insect pest populations.In this study,the screening of entomopathogenic fungi for control of C.lapathi is reported through the evaluation of virulence of four fungal Beauveria bassiana(CFCC81428,CFCC83116,CFCC83486,CFCC87297)strains,one B.brongniartii(CFCC83487) strain and one Metarhizium anisopliae(CFCC88953) strain.The virulence of the different strains was appraised by correct mortality rate,cumulative mortality rate,median lethal concentration(LC_(50)) and median lethal time(LT_(50)).B.bassiana strains CFCC81428 and CFCC83116 were the most virulent among the six strains with a mortality up to 100%,and the LT_(50) were 2.7 and 3.1 days.Five conidia concentrations of three strains(CFCC81428,CFCC83116 and CFCC87298) that caused high virulence was screened for dose-relationship.Their effect on controlling C.lapathi larvae were also determined under field condition by brushing conidia suspensions on C.lapathi larvae infested in a poplar trunk.The cumulative rate in the field was lower than those obtained from the laboratory,but the order of the virulence of different strains did not change.Mortality in all three strains occurred at their highest concentration(1.0 × 10^(8) conidia mL^(-1)).Under field conditions,the CFCC81428 strain was the most effective,causing mortalities of 80.3% and 75.2%in two plots in Beipiao and Lindian counties,respectively,followed by CFCC83116(69.1%,66.6%) and CFCC87298(60.7%,59.3%).Based on our results,the B.bassiana strain CFCC81428 has the potential as a biological insecticide to control C.lapathi larvae.
基金supported by the Key Project of National Natural Science Foundation of China(30530550)
文摘The objective of this study was to construct the infectious clone of encephalomyocarditis virus (EMCV) BJC3 strain.The genomic cDNA of the virus was amplified by three overlapping segments using RT-PCR,and cloned into low-copy plasmid pWSK29 to construct the full-length cDNA clone pWSKBJC3/ w.The pWSKBJC3/w was in vitro transcribed and transfected into BHK-21 cells to rescue the virus.The results showed that the full-length cDNA clone was infectious and the virus could be rescued in BHK-21 cells.The rescued virus designated RvBJC3W was identified by RT-PCR and indirect immunofluorescence assay(IFA).The rescued virus had similar growth characteristics to its parental virus BJC3 and retained pathogenicity for mice.Our results indicate that the first infectious cDNA clone of EMCV in China has been successfully established and provides an essential tool for investigating the molecular basis of pathogenicity of EMCV.
文摘BACKGROUND： With mechanical ventilation widely used in intensive care unit, the ventilator associated pneumonia （VAP） has become a common and serious complication in critically ill patients. Compared with adults, the incidence of VAP and the mortality are higher in children in pediatric intensive care unit （PICU） because of immune deficiency, severe basic diseases, and increased use of artificial airway or mechanical ventilation. Hence it is of significance to study the epidemiology and changes of antibacterial susceptibility in order to reduce the incidence and mortality of VAP in children.METHODS： From January 2008 to June 2010, 2758 children were treated in PICU of Wuhan Children＇s Hospital. Among them, 171 received mechanical ventilation over 48 hours in PICU, and 46 developed VAP. The distribution and drug-resistance pattern of the pathogenic bacteria isolated from lower respiratory tract aspirations were analyzed. RESULTS：A total of 119 pathogenic microbial strains were isolated. Gram-negative bacilli （G-） were the most （65.55%）, followed by fungi （21.01%） and gram-positive cocci （G~, 13.45%）. Among them, the most common pathogens were Acinetobacter baummannii, Escherichia coli, Klebsiella pneumoniae, candida albicans and coagulase-negative staphylococci. Antibiotic susceptibility tests indicated that the multiple drug-resistances of G- and G＋to antibiotics were serious. Most of G- was sensitive to ciprofloxacin, amikacin, imipenem, meropenem, cefoperazone-sulbactam and piperacillin-tazobactam. The susceptibility of G＋ to vancomycin, teicoplanin and linezolid were 100%. Fungi were almost sensitive to all the antifungal agents. The primary pathogens of VAP were G-, and their multiple drug-resistances were serious. CONCLUSION： In clinical practice we should choose the most sensitive drug for VAP according to pathogenic test.
文摘Listeria monocytogenes is an important foodborne pathogen responsible for listeriosis,a fatal disease.It is widely distributed in various foods and environmental sources.In this review,we focused on addressing PCR-based technologies,including conventional PCR,qPCR and droplet digital PCR(ddPCR).Specifically,we described(a)conventional PCR and mono-,duplex-and multiplex-qPCR methodologies;(b)development and applications of gene HlyA-,Iap-,PrfA–and SsrA-based conventional and qPCR assays as well as PCR assays targeting newly identified gene targets for specific detection of L.monocytogenes;differentiation of viable from dead L.monocytogenes by qPCR in conjugation with propidium monoazide pretreatment;PCR-based serotype identification of L.monocytogenes isolates;PCR-based detection of L.ivanovii,infecting ruminants,differentiation of L.monocytogenes from other Listeria species;and sigB-gene based PCR identification of Listeria spp;(c)applications of ddPCR in detection of L.monocytogenes;and(d)application of qPCR assays in detection and subtyping of L.monocytogenes in milk and dairy products;meats,meat products and meat-processing environment;and seafood,seafood products and processing environment.Our goal was to provide a relatively comprehensive overview of PCR-based methodologies available in detection,characterization and subtyping of various strains of L.monocytogenes in foods and environmental sources.
基金This paper was supported by National Natural Science Foundation of China （No.30271083）.
文摘DNA was extracted from the strain of pathogen of poplar leaf blight using a modified CTAB method. ITS sequence （601bp） was initially amplified from the pathogen by using the universal primers ITSl and ITS4 （registered No, DQ011257）. Comparing to the nucleotide sequences acquired from GenBank database, the strain is clustered into the homogeneity with Alternaria alternate （AY787684） and Alternaria alternate （AY354228）, with a homology of 98%, thus the strain was checked as Alternaria alternata （Fr.） Keissler. The optimal conditions for conidia germination and mycelium growth of the pathogen were tested, The optimal temperature for conidia germinating and mycelium growth is 25℃, and the optimal pH value is 6. Mycelium grows rather slowly at 10℃ and 30℃ and growth stops at above 35 ℃. Among the six culture mediums tested, PDA ＋ poplar leaf juice medium is most favorable for mycelium growth.
文摘Chinese hackberry(Celtis sinensis Pers.)is an adaptable species widely growing in southern China.The symptoms of canker on stems of seedlings were discovered mid-July 2017 in Shuyang,Jiangsu Province.The diseased portions of the stems were dark brown due to discoloured xylem.Some seedlings showed symptoms of wilting,leaf fall,twig dieback,and tissue discolouration.The outbreak period was concentrated in July and August,suggesting that the disease spread during summer months.Possible fungal causal agents were isolated from naturally infected canker tissue and discoloured xylem.The isolate from xylem tissue with a high frequency(>50%)was named Ls7 type.Pathogenicity tests were carried out on 4-yearold seedlings.The symptoms of canker began to develop 20 days after inoculation with Ls7 isolate and by day 35,there were dark,enlarged longitudinal lesions.A phylogenetic tree of the isolate was developed using the internal transcribed spacer,elongation factor-1α(tef1-α),β-tubulin gene(TUB)and RNA polymerase II subunit primer genes(RPB2).Based on morphological features and phylogenetic information,the pathogen was identifi ed as Lasiodiplodia pseudotheobromae.This is the fi rst report of L.pseudotheobromae causing canker on Chinese hackberry stems in China.
