Genetics and Genomics of Sulfate Respiration in Desulfovibrio

Abstract

Bacteria that have evolved to use sulfate as a terminal electron acceptor must commit to spending energy for sulfate activation before there is a return on the investment allowing net energy gain. How sulfate is used and how electron flow is controlled have provided challenging topics for research for many years. Having the complete genome sequences of several of these bacteria is a monumental step in the elucidation of these questions. This information has provided the tools for determining the quantity of transcripts for genes under defined growth conditions, not just the relative changes in transcripts in two growth conditions. A comparison of the hybridization signal of messenger RNA with that of genomic DNA with oligonucleotide microarrays of all open reading frames reveals the differences in steady-state levels of transcripts for each gene. Growth of Desulfovibrio vulgaris Hildenborough on defined medium with lactate as a carbon and reductant source and with sulfate as the electron acceptor has been examined by this procedure for levels of gene expression. Relative functional importance was inferred from the levels of gene transcription, in spite of the recognized limitations of this interpretation. Not surprisingly, genes encoding established functions for sulfate reduction were highly expressed. However, the high molecular mass c-type cytochrome genes thought to encode a most important transmembrane electron conduit for sulfate reduction were expressed at quite low levels.