Genome analysis of several marine, magnetotactic bacterial strains by pulsed-field gel electrophoresis

The genomic DNA of three strains of marine magnetotactic bacteria, includin g two facultatively anaerobic vibrios, strains MV-1 and MV-2, and the micro aerophilic coccus, strain MC-1, was analyzed by pulsed-field gel electropho resis (PFGE). Digestion of the genomic DNA of strain MV-1 by the restrictio n endonucleases Avl II, BamHI, HindIII, NheI, SalI, SfiI, SgfI, SgrAI, and XbaI resulted in a large number of fragments below 400 kb that were difficu lt to resolve by PFGE. Digestion of MV-1 DNA with NotI and RsrII resulted i n no fragments. Treatment of genomic DNA of strains MV-1 and MV-2 with PacI , PmeI, and SpeI yielded a manageable number of fragments (ca. 20) that wer e relatively easily resolved with PFGE, while PacI and SpeI were effective for strain MC-1. There was no evidence for the presence of plasmids and lin ear chromosomes in any of the strains, and strains MV-1 and MV-2 appear to contain a single, circular chromosome. Genome sizes of strains MV-1, MV-2, and MC-1 were estimated to be between 3.6 and 3.9 Mb (mean +/- SD; 3.7 +/- 0.2), 3.3 and 3.7 Mb (3.6 rfi 0.2), and 4.3 and 4.7 Mb (4.5 +/- 0.3), respe ctively. The restriction fragment patterns of the vibrioid strains MV-1 and MV-2 were extremely similar, suggesting that the strains are closely relat ed.