Cloning and assembly strategies in microbial genome projects
Résumé
The knowledge of an entire genome sequence not only provides a wealth of data, but also specific information that can not be obtained by other approaches. Only after the completion of genome projects did it become obvious that many genes had not been identified by classical genetics. These included many genes that do not share similarities with known genes in databases, paralogous genes leading to redundancy of gene function, genes corresponding to potential new drug targets (Arigoni et al., 1998R3 ) and inactive genes resulting from reductive evolution (Andersson et al., 1998R2 ). Whole-genome sequencing has revealed important information on the organization of genomes. These include the G+C content and its variation within the genome, leading to the identification of DNA regions acquired by horizontal gene transfer, the presence of repeated elements or insertion elements, the discovery of new pathogenicity islands in pathogenic bacteria and the identification of new operons, genome polarity, and the identification of origin(s) of replication. Genome projects also can be starting points for other projects such as metabolic reconstruction (Selkov et al., 1997R58 ) and the systematic functional analysis of all of the genes of an organism which are, for example, currently being carried out for Saccharomyces cerevisiae (Dujon, 1998R18 ) and Bacillus subtilis (see the INRA web site; Table 1T1).