To date among the sulfate-reducing bacteria, no bona fide member of the species desulfuricans has been sequenced. Desulfovibrio desulfuricans subsp. desulfuricans str. ATCC 27774 was isolated by the late Marvin Bryant as the first well documented sulfate-reducing bacterium capable of growing with dissimilatory nitrate reduction (1). The c-type cytochrome shown to be responsible for nitrite reduction was identified as the first nitrite reductase of this type. The sulfate-reducing bacteria are known to require medium poised at a redox potential of about -100 mV to initiate growth with sulfate, yet here is a strain also capable of growing with nitrate in medium much more oxidized. The changes in cellular metabolism that allow this switch in terminal electron acceptors are not known. Work with 27774 showed that the nitrate reduction pathway was not expressed while sulfate was available (1). Alternatively, the sulfate reduction pathway was constitutively expressed when the cells were growing with nitrate reduction. D. desulfuricans 27774 holds the distinction of also being the first strain among the Deltaproteobacteria to exhibit generalized transduction (2). A small defective bacteriophage, Dd1, was described for this strain that packaged apparently random bacterial DNA in fragments of about 13.5 kb and transferred the DNA to appropriate recipient strains of 27774. Plaque-forming ability for Dd1 was not detectable, a finding consistent with the small size of the phage particle head. In the absence of a plaquing phenotype, the development of Dd1 into an in vitro packaging vector was not pursued. This strain has become the focus of a number of biochemical efforts to isolate functional membrane-associated electron transport complexes. The DsrMKJOP complex thought to function as the electron carrier for sulfite reduction has been isolated and characterized. In addition, a novel membrane-bound complex with homology to heterodisulfide reductases has been purified. Having sequence information to bolster the elegant biochemistry would increase the rate at which understanding occurs.