Genomic organization analysis of acidophilic chemolithotrophic bacteria using pulsed field gel electrophoretic techniques

The genomic organization of acidophilic chemolithotrophic bacteria belongin g to the genus Thiobacillus, Thiomonas and Leptospirillum was studied using pulsed field gel electrophoresis techniques (PFGE). The electrophoretic an alysis of intact DNA prepared from different strains showed that all have a circular chromosome, with sizes ranging from 1.9 Mb for Leptospirillum fer rooxidans ATCC 49879, the smallest genome for an acidophilic strict chemoli thoautotrophic microorganism, to 3.8 Mb for Thiomonas cuprina DSM 5495, the largest in this study. The number of extrachromosomal elements present var ied from none, as observed in several isolates of Leptospirillum ferrooxida n, to five in Thiobacillus thiooxidans ATCC 8085. The mixotroph Thiomonas c uprina DSM 5495 was found to have a linear 50 kb megaplasmid which was indu cible when the bacteria was grown in chemolithotrophic conditions. Low-freq uency restriction fragment analysis (LFRFA) of different acidophilic chemol ithotrophs and related species was carried out by PFGE to determine macrore striction patterns for rare cutters (SpeI, XbaI, SwaI, PmeI), which were th en used for taxonomic identification (karyotyping), genome size determinati on, and generation of physical and generic maps. (C) Societe francaise de b iochimie et biologie moleculaire / Elsevier, Paris.