Phylogeny and distribution of the soxB gene among thiosulfate-oxidizing bacteria

A PCR protocol for the detection of sulfur-oxidizing bacteria based on soxB genes that are essential for thiosulfate oxidation by sulfur oxidizing bac teria of various phylogenetic groups which use the 'Paracoccus sulfur oxida tion' pathway was developed. Five degenerate primers were used to specifica lly amplify fragments of soxB genes from different sulfur-oxidizing bacteri a previously shown to oxidize thiosulfate. The PCR yielded a soxB fragment of approximately 1000 bp from most of the bacteria. Amino acid and nucleoti de sequences of soxB from reference strains as well as from new isolates an d environmental DNA from a hydrothermal vent habitat in the North Fiji Basi n were compared and used to infer relationships of soxB between sulfur-oxid izing bacteria belonging to various 16S rDNA-based phylogenetic groups. Maj or phylogenetic lines derived From 16S rDNA were confirmed by soxB phylogen y. Thiosulfate-oxidizing green sulfur bacteria formed a coherent group by t heir soxB sequences. Likewise, clearly separated branches demonstrated the distant relationship of representatives of alpha-, beta-, and gamma -Proteo bacteria including representative species of the former genus Thiobacillus (now Halothiobacillus-gamma -Proteobacteria, Thiobacillus-beta -Proteobacte ria and Starkeya-alpha -Proteobacteria). This general picture emerged altho ugh apparent evidence for lateral transfer of the soxB gene is indicated an d comparison of soxB phylogeny and 16S rDNA phylogeny points to the signifi cance of this gene transfer in hydrothermal vent bacterial communities of t he North Fiji Basin. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Microbiological Societies.