CONSERVATION OF THE GENES FOR DISSIMILATORY SULFITE REDUCTASE FROM DESULFOVIBRIO-VULGARIS AND ARCHAEOGLOBUS-FULGIDUS ALLOWS THEIR DETECTION BY PCR

The structural genes for dissimilatory sulfite reductase (desulfoviridin) from Desulfovibrio vulgaris Hildenborough were cloned as a 7.2-kbp SacII DNA fragment. Nucleotide sequencing indicated the presence of a third gene, encoding a protein of only 78 amino acids, immediately downstream from the genes for the alpha and beta subunits (dsvA and dsvB). We designated this protein DsvD and the gene encoding it the dspD gene. The alpha- and beta-subunit sequences are highly homologous to those of the dissimilatory sulfite reductase from Archaeoglobus fulgidus, a thermophilic archaeal sulfate reducer, which grows optimally at 83 degrees C. A gene with significant homology to dsvD was also found immediately downstream from the dsrAB genes of A. fulgidus. The remarkable conservation of gene arrangement and sequence across domain (bacterial versus archaeal) and physical (mesophilic versus thermophilic) boundaries indicates an essential role for DsvD in dissimilatory sulfite reduction and allowed the construction of conserved deoxyoligonucleotide primers for detection of the dissimilatory sulfite reductase genes in the environment.