A comparative study on the phenotypic and genetic characteristics among Acidithiobacillus ferrooxidans （AF2）, a typic strain ATCC23270 and a previously isolated strain AF3 was performed. AF2 can use ferrous ion （F...A comparative study on the phenotypic and genetic characteristics among Acidithiobacillus ferrooxidans （AF2）, a typic strain ATCC23270 and a previously isolated strain AF3 was performed. AF2 can use ferrous ion （Fe^2＋） or elemental sulfur （S^0） as sole energy source, but oxidizes So more effectively than Fe^2＋, which is different from ATCC23270 and AF3. The G＋C content of AF2 is 51.8% （molar fraction）, however, ATCC23270 and AF3 strains have G＋C content of 63.7% and 64.8% （molar fraction）, respectively. The DNA-DNA hybridization results show that AF2 has 41.53% and 52.38% genome similarity to ATCC 23270 and AF3, respectively, but AF3 has a high genome similarity of 89.86% to ATCC 23270 strain. Rusticyanin （rus） and subunit III of aa3-type cytochrome oxidase （coxC） genes are not detected in AF2, but Fe^2＋ oxidase （iro） gene can be detected. To understand the genomic organization of iro gene, a cosmid library of AF2 genome was constructed and iro gene-containing clone was screened. The sequencing result shows that although the nucleotide sequence of iro gene in AF2 is completely identical to that of ATCC 23270 strain, its genomic organization is different from that of ATCC 23270. In AF2, iro is located at downstream ofpurA gene, while it is located at downstream ofpetC-2 gene in ATCC 23270 strain. These results indicate that AF2 is a novel strain ofA. ferrooxidans, and that phenotypic differences among the strains ofA. ferrooxidans are closely correlated with their genetic polymorphisms.展开更多
The classical job shop scheduling problem(JSP) is the most popular machine scheduling model in practice and is known as NP-hard.The formulation of the JSP is based on the assumption that for each part type or job ther...The classical job shop scheduling problem(JSP) is the most popular machine scheduling model in practice and is known as NP-hard.The formulation of the JSP is based on the assumption that for each part type or job there is only one process plan that prescribes the sequence of operations and the machine on which each operation has to be performed.However,JSP with alternative machines for various operations is an extension of the classical JSP,which allows an operation to be processed by any machine from a given set of machines.Since this problem requires an additional decision of machine allocation during scheduling,it is much more complex than JSP.We present a domain independent genetic algorithm(GA) approach for the job shop scheduling problem with alternative machines.The GA is implemented in a spreadsheet environment.The performance of the proposed GA is analyzed by comparing with various problem instances taken from the literatures.The result shows that the proposed GA is competitive with the existing approaches.A simplified approach that would be beneficial to both practitioners and researchers is presented for solving scheduling problems with alternative machines.展开更多
基金Project(200805032) supported by the Scientific Research Program of Marine Public Welfare Industry of China
文摘A comparative study on the phenotypic and genetic characteristics among Acidithiobacillus ferrooxidans （AF2）, a typic strain ATCC23270 and a previously isolated strain AF3 was performed. AF2 can use ferrous ion （Fe^2＋） or elemental sulfur （S^0） as sole energy source, but oxidizes So more effectively than Fe^2＋, which is different from ATCC23270 and AF3. The G＋C content of AF2 is 51.8% （molar fraction）, however, ATCC23270 and AF3 strains have G＋C content of 63.7% and 64.8% （molar fraction）, respectively. The DNA-DNA hybridization results show that AF2 has 41.53% and 52.38% genome similarity to ATCC 23270 and AF3, respectively, but AF3 has a high genome similarity of 89.86% to ATCC 23270 strain. Rusticyanin （rus） and subunit III of aa3-type cytochrome oxidase （coxC） genes are not detected in AF2, but Fe^2＋ oxidase （iro） gene can be detected. To understand the genomic organization of iro gene, a cosmid library of AF2 genome was constructed and iro gene-containing clone was screened. The sequencing result shows that although the nucleotide sequence of iro gene in AF2 is completely identical to that of ATCC 23270 strain, its genomic organization is different from that of ATCC 23270. In AF2, iro is located at downstream ofpurA gene, while it is located at downstream ofpetC-2 gene in ATCC 23270 strain. These results indicate that AF2 is a novel strain ofA. ferrooxidans, and that phenotypic differences among the strains ofA. ferrooxidans are closely correlated with their genetic polymorphisms.
文摘The classical job shop scheduling problem(JSP) is the most popular machine scheduling model in practice and is known as NP-hard.The formulation of the JSP is based on the assumption that for each part type or job there is only one process plan that prescribes the sequence of operations and the machine on which each operation has to be performed.However,JSP with alternative machines for various operations is an extension of the classical JSP,which allows an operation to be processed by any machine from a given set of machines.Since this problem requires an additional decision of machine allocation during scheduling,it is much more complex than JSP.We present a domain independent genetic algorithm(GA) approach for the job shop scheduling problem with alternative machines.The GA is implemented in a spreadsheet environment.The performance of the proposed GA is analyzed by comparing with various problem instances taken from the literatures.The result shows that the proposed GA is competitive with the existing approaches.A simplified approach that would be beneficial to both practitioners and researchers is presented for solving scheduling problems with alternative machines.
