Culture-independent analysis of desulfovibrios in the human distal colon of healthy, colorectal cancer and polypectomized individuals

The production of hydrogen sulphide, an end product of metabolism by the sulphate-reducing bacteria (SRB) has been cited as a potential aetiological agent in gastrointestinal disease. Quantitative PCR (Q-PCR) assays to enumerate desulfovibrios from two gastrointestinal disease groups: colorectal cancer (CRC) n =27 and polypectomized individuals (PP) n =27, and two healthy control groups, elderly (H1) n =8 and young adults (H2) n =30 was performed. Analysis of Desulfovibrio sp. diversity using the dissimilarity sulphite reductase ( dsrAB ) gene as a molecular marker was also undertaken. Q-PCR detected Desulfovibrio sp. in all samples and no significant difference was observed for PP, H1, H2 with gene copy numbers of Desulfovibrio sp. averaging at 10⁶ g⁻¹ of faeces. Significantly reduced numbers of Desulfovibrio sp. were observed for CRC (10⁵ g⁻¹) compared with both PP and H2 groups ( P <0.05). Diversity analysis indicated that a low Desulfovibrio sp. diversity and the predominance of Desulfovibrio piger was a feature of both healthy and disease groups. In addition, a dsrAB gene sequence distantly related to a Gram-positive SRB was also recovered, highlighting the importance of cultivation-independent techniques for furthering our understanding of the diversity of the human gastrointestinal ecosystem.     

化学杀菌剂对太原集中供热水体中有害菌群杀灭作用研究

研究了戊二醛、十二烷基二甲基苄基氯化铵对太原热网循环水中脱硫弧菌、鞘铁细菌、棒状杆菌、微球菌、葡萄球菌、芽孢杆菌和不动细菌等7类细胞的杀菌效果,结果表明：（1）不同浓度的戊二醛与十二烷基二甲基苄基氯化铵对7类细胞的杀菌效果差异极显著,而且随着杀菌剂浓度的增加这些细菌的死亡率呈线性上升;（2）戊二醛的杀菌浓度在100mg/L较为适宜,而二十烷基二甲基苄基氯化铵对脱硫弧菌和鞘铁细菌的杀菌浓度以100mg/L为宜,而对其余5类细菌的浓度以120mg/L较好;（3）戊二醛的杀菌效果明显优于十二烷基二甲基苄基氯化铵。     

Selection for novel,acid-tolerant <Emphasis Type="Italic">Desulfovibrio</Emphasis> spp. from a closed Transbaikal mine site in a temporal pH-gradient bioreactor

Almost all the known isolates of acidophilic or acid-tolerant sulphate-reducing bacteria (SRB) belong to the spore-forming genus Desulfosporosinus in the Firmicutes. The objective of this study was to isolate acidophilic/acid-tolerant members of the genus Desulfovibrio belonging to deltaproteobacterial SRB. The sample material originated from microbial mat biomass submerged in mine water and was enriched for sulphate reducers by cultivation in anaerobic medium with lactate as an electron donor. A stirred tank bioreactor with the same medium composition was inoculated with the sulphidogenic enrichment. The bioreactor was operated with a temporal pH gradient, changing daily, from an initial pH of 7.3 to a final pH of 3.7. Among the bacteria in the bioreactor culture, Desulfovibrio was the only SRB group retrieved from the bioreactor consortium as observed by 16S rRNA-targeted denaturing gradient gel electrophoresis. Moderately acidophilic/acid-tolerant isolates belonged to Desulfovibrio aerotolerans-Desulfovibrio carbinophilus-Desulfovibrio magneticus and Desulfovibrio idahonensis-Desulfovibrio mexicanus clades within the genus Desulfovibrio. A moderately acidophilic strain, Desulfovibrio sp. VK (pH optimum 5.7) and acid-tolerant Desulfovibrio sp. ED (pH optimum 6.6) dominated in the bioreactor consortium at different time points and were isolated in pure culture.     

Desulfovibrio longus sp. nov., a sulfate-reducing bacterium isolated from an oil-producing well.

A novel type of sulfate-reducing bacteria with unusual morphology was isolated from an oil-producing well in the Paris Basin. The cells of this bacterium, strain SEBR 2582T (T = type strain), are long, thin, flexible rods, contain desulfoviridin, and are physiologically similar to members of the genus Desulfovibrio. On the basis of 16S rRNA sequence data, this strain should be included in the genus Desulfovibrio. However, strain SEBR 2582T differs from other members of this genus morphologically, physiologically, and phylogenetically. Thus, a new species, Desulfovibrio longus sp. nov., is proposed for this organism.     

Properties of Desulfovibrio carbinolicus sp. nov. and Other Sulfate-Reducing Bacteria Isolated from an Anaerobic-Purification Plant

Several sulfate-reducing microorganisms were isolated from an anaerobic-purification plant. Four strains were classified as Desulfovibrio desulfuricans, Desulfovibrio sapovorans, Desulfobulbus propionicus, and Desulfovibrio sp. The D. sapovorans strain contained poly-beta-hydroxybutyrate granules and seemed to form extracellular vesicles. A fifth isolate, Desulfovibrio sp. strain EDK82, was a gram-negative, non-spore-forming, nonmotile, curved organism. It was able to oxidize several substrates, including methanol. Sulfate, sulfite, thiosulfate, and sulfur were utilized as electron acceptors. Pyruvate, fumarate, malate, and glycerol could be fermented. Because strain EDK82 could not be ascribed to any of the existing species, a new species, Desulfovibrio carbinolicus, is proposed. The doubling times of the isolates were determined on several substrates. Molecular hydrogen, lactate, propionate, and ethanol yielded the shortest doubling times (3.0 to 6.3 h). Due to the presence of support material in an anaerobic filter system, these species were able to convert sulfate to sulfide very effectively at a hydraulic retention time as short as 0.5 h.     

Desulfovibrio Africans sp. n., a new dissimilatory sulfate-reducing bacterium

Campbell, L. Leon (University of Illinois, Urbana), Mary A. Kasprzycki, and John R. Postgate. Desulfovibrio africanus sp. n., a new dissimilatory sulfate-reducing bacterium. J. Bacteriol. 92:1122-1127. 1966.-The strains Benghazi and Walvis Bay can be distinguished from 40 strains of Desulfovibrio and from D. gigas on the basis of morphological and immunological studies. Electron microscopy revealed polar lophotrichous flagellation similar to that of D. gigas but different from the characteristic single polar flagellum of the 40 strains of Desulfovibrio. Immunological evidence shows that the two strains are related to members of the genus Desulfovibrio but possess several common antigenic components not present in the other strains tested. The deoxyribonucleic acid of both strains has a buoyant density of 1.724 g/cc and a guanine plus cytosine content of 60.2%. Cell-free extracts of both organisms show absorption bands of cytochrome c(3) and desulfoviridin, characteristic for Desulfovibrio. The two organisms carry out the sulfate-linked lactate fermentation and neither will grow in the absence of sulfate. Both strains contain the enzymes of the dissimilatory pathway of sulfate reduction. Therefore, these studies have demonstrated that the Benghazi and Walvis Bay strains should be regarded as taxonomically distinct from other species of Desulfovibrio.     

Phospholipid fatty acid and infra-red spectroscopic analysis of a sulphate-reducing consortium

Abstract In order to validate unusual fatty acids as biomarkers for sulphate-reducing bacteria, selective conditions were arranged for the enrichment of a marine glutamate-fermenting bacterium which made hydrogen and acetate available for oxidation via the respiration of sulphate. Under these conditions the complete oxidation of glutamate via sulphate reduction accounted for 84% of the available electron equivalents. Fatty acid biomarkers for hydrogen-oxidizing Desulfovibrio sp. (iso 17:1w7c and branched monoenoics) and for acetate-oxidizing Desulfobacter (10 methyl 16:0) were detected in the enrichment. These biomarkers were demonstrated in pure cultures of Desulfovibrio sp. and Desulfobacter sp. obtained from the enrichment. The predominant glutamate-fermenting bacterium isolated from the consortium contained no branched ester-linked phospholipid fatty acids, and produced acetate and hydrogen. With energy limitation the enriched consortium produced increased amounts of extracellular polysaccharide and the endogenous storage lipid poly-beta-hydroxybutyrate as detected with Fourier transform/infra-red (FT-IR) spectroscopy.     

Sulphate-reducing bacteria,palladium and the reductive dehalogenation of chlorinated aromatic compounds

The surfaces of cells of Desulfovibrio desulfuricans,Desulfovibrio vulgaris and a new strain, Desulfovibrio sp. `Oz-7' were used to manufacturea novel bioinorganic catalyst via the reduction of Pd(II) to Pd(0) at the cell surface usinghydrogen as the electron donor. The ability of the palladium coated (palladised) cells to reductivelydehalogenate chlorophenol and polychlorinated biphenyl species was demonstrated. Dried, palladisedcells of D. desulfuricans, D. vulgaris and Desulfovibrio sp. `Oz-7'were more effective bioinorganic catalysts than Pd(II) reduced chemically under H₂ orcommercially available finely divided Pd(0). Differences were observed in the catalyticactivity of the preparations when compared with each other. Negligible chloride release occurredfrom chlorophenol and polychlorinated biphenyls using biomass alone.     

Culture and identification of Desulfovibrio spp. from corals infected by black band disease on Dominican and Florida Keys reefs

Black band disease (BBD) of corals is characterized as a pathogenic microbial consortium composed of a wide variety of microorganisms. Together, many of these microorganisms contribute to an active sulfur cycle that produces anoxia and high levels of sulfide adjacent to the coral surface, conditions that are lethal to coral tissue. Sulfate-reducing bacteria, as sulfide producers, are an important component of the sulfur cycle and the black band community. Previous molecular survey studies have shown multiple Desulfovibrio species present in BBD but with limited consistency between bacterial species and infections. In this study we compared 16S rRNA gene sequences of sulfate-reducing bacteria selectively cultured from 6 BBD bands on 4 coral species, Diploria clivosa, D. strigosa, D. labyrinthiformes, and Siderastrea siderea, in the Florida Keys and Dominica. The 16S rRNA gene sequences were obtained through direct sequencing of PCR products or by cloning. A BLAST search revealed that 8 out of 10 cultures sequenced were highly homologous to Desulfovibrio sp. strain TBP-1, a strain originally isolated from marine sediment. Although the remaining 2 sequences were less homologous to Desulfovibrio sp. strain TBP-1, they did not match any other sulfate-reducing (or other) species in GenBank.     

Isolation from estuarine sediments of a Desulfovibrio strain which can grow on lactate coupled to the reductive dehalogenation of 2,4, 6-tribromophenol

Strain TBP-1, an anaerobic bacterium capable of reductively dehalogenating 2,4,6-tribromophenol to phenol, was isolated from estuarine sediments of the Arthur Kill in the New York/New Jersey harbor. It is a gram-negative, motile, vibrio-shaped, obligate anaerobe which grows on lactate, pyruvate, hydrogen, and fumarate when provided sulfate as an electron acceptor. The organism accumulates acetate when grown on lactate and sulfate, contains desulfoviridin, and will not grow in the absence of NaCl. It will not utilize acetate, succinate, propionate, or butyrate for growth via sulfate reduction. When supplied with lactate as an electron donor, strain TBP-1 will utilize sulfate, sulfite, sulfur, and thiosulfate for growth but not nitrate, fumarate, or acrylate. This organism debrominates 2-, 4-, 2,4-, 2,6-, and 2,4,6-bromophenol but not 3- or 2,3-bromophenol or monobrominated benzoates. It will not dehalogenate monochlorinated, fluorinated, or iodinated phenols or chlorinated benzoates. Together with its physiological characteristics, its 16S rRNA gene sequence places it in the genus Desulfovibrio. The average growth yield of strain TBP-1 grown on a defined medium supplemented with lactate and 2,4,6-bromophenol is 3.71 mg of protein/mmol of phenol produced, and the yield was 1.42 mg of protein/mmol of phenol produced when 4-bromophenol was the electron acceptor. Average growth yields (milligrams of protein per millimole of electrons utilized) for Desulfovibrio sp. strain TBP-1 grown with 2,4,6-bromophenol, 4-bromophenol, or sulfate are 0.62, 0.71, and 1.07, respectively. Growth did not occur when either lactate or 2,4,6-bromophenol was omitted from the growth medium. These results indicate that Desulfovibrio sp. strain TBP-1 is capable of growth via halorespiration.     

Syntrophic growth on formate: a new microbial niche in anoxic environments

Anaerobic syntrophic associations of fermentative bacteria and methanogenic archaea operate at the thermodynamic limits of life. The interspecies transfer of electrons from formate or hydrogen as a substrate for the methanogens is key. Contrary requirements of syntrophs and methanogens for growth-sustaining product and substrate concentrations keep the formate and hydrogen concentrations low and within a narrow range. Since formate is a direct substrate for methanogens, a niche for microorganisms that grow by the conversion of formate to hydrogen plus bicarbonate--or vice versa--may seem unlikely. Here we report experimental evidence for growth on formate by syntrophic communities of (i) Moorella sp. strain AMP in coculture with a thermophilic hydrogen-consuming Methanothermobacter species and of (ii) Desulfovibrio sp. strain G11 in coculture with a mesophilic hydrogen consumer, Methanobrevibacter arboriphilus AZ. In pure culture, neither Moorella sp. strain AMP, nor Desulfovibrio sp. strain G11, nor the methanogens grow on formate alone. These results imply the existence of a previously unrecognized microbial niche in anoxic environments.     

Cometabolic Transformation and Cleavage of Nitrodiphenylamines by Three Newly Isolated Sulfate-Reducing Bacterial Strains

Three sulfate-reducing bacterial strains (Desulfovibrio sp. strain SHV, Desulfococcus sp. strain WHC, and Desulfomicrobium sp. strain WHB) with the capacity to cometabolize 2-nitrodiphenylamine, 4-nitrodiphenylamine, and 2,4-dinitrodiphenylamine were newly isolated. Before breaking down the diphenylamine structure, these strains cometabolically reduce the nitrodiphenylamines to the corresponding aminodiphenylamines during anaerobic oxidation of the growth substrate lactate (Desulfovibrio strain SHV and Desulfomicrobium strain WHC) or benzoate (Desulfococcus strain WHB), leading to the formation of aniline and a smaller quantity of methylaniline. These compounds were not further metabolized by the sulfate reducers. The anaerobic metabolism of aminodiphenylamines also led to the formation of heterocyclic condensation products such as phenazine and acridine derivatives, provided that they contained an amino group in the ortho position of the diphenylamine (e.g., 2-aminodiphenylamine or 2,4-diaminodiphenylamine). In addition, low levels of indole and benzothiazole derivatives were identified, but these also were not further metabolized by the three sulfate-reducing strains.     

16S rRNA gene diversity of attached and unattached bacteria in boreholes along the access tunnel to the Äspö hard rock laboratory, Sweden

Abstract: A total of 155 16S rRNA genes that were cloned from unattached and attached bacteria in nine boreholes down to 626 m below ground were partially sequenced. Attached bacteria were examined with scanning electron microscopy (SEM). The distribution of the 16S rRNA genes found was related to the different types of groundwaters studied. Several of the sequences obtained could be identified on genus level as one of the genera Acinetobacter, Bacillus, Desulfovibrio or Thiomicrospira . The 16S rRNA genes from 20 selected isolates were closely related to the sulphate reducers Desulfomicrobium baculatum or Desulfovibrio sp., the iron reducer Shewanella putrefaciens , or distantly related to the Gram-positive genus Eubacterium . Viable counts confirmed the presence of sulphate-reducing bacteria.     

Oxidation of benzaldehydes to benzoic acid derivatives by three Desulfovibrio strains

Desulfovibrio vulgaris Marburg, "Desulfovibrio simplex" XVI, and Desulfovibrio sp. strain MP47 used benzaldehydes such as vanillin, 3,4,5-trimethoxybenzaldehyde, protocatechualdehyde, syringaldehyde, p-anisaldehyde, p-hydroxybenzaldehyde, and 2-methoxybenzaldehyde as electron donors for sulfate reduction and carbon dioxide and/or components of yeast extract as carbon sources for cell synthesis. The aldehydes were oxidized to their corresponding benzoic acids. The three sulfate reducers oxidized up to 7 mM vanillin and up to 4 mM p-anisaldehyde. Higher concentrations of vanillin or p-anisaldehyde were toxic. In addition, pyridoxal hydrochloride and o-vanillin served as electron donors for sulfate reduction. Salicylaldehyde, pyridine-2-aldehyde, pyridine-4-aldehyde, and 4-hydroxy-3-methoxybenzylalcohol were not oxidized. No molecular hydrogen was detected in the gas phase. The oxidized aldehydes were not further degraded.     

Oxidation of benzaldehydes to benzoic acid derivatives by three Desulfovibrio strains.

Desulfovibrio vulgaris Marburg, "Desulfovibrio simplex" XVI, and Desulfovibrio sp. strain MP47 used benzaldehydes such as vanillin, 3,4,5-trimethoxybenzaldehyde, protocatechualdehyde, syringaldehyde, p-anisaldehyde, p-hydroxybenzaldehyde, and 2-methoxybenzaldehyde as electron donors for sulfate reduction and carbon dioxide and/or components of yeast extract as carbon sources for cell synthesis. The aldehydes were oxidized to their corresponding benzoic acids. The three sulfate reducers oxidized up to 7 mM vanillin and up to 4 mM p-anisaldehyde. Higher concentrations of vanillin or p-anisaldehyde were toxic. In addition, pyridoxal hydrochloride and o-vanillin served as electron donors for sulfate reduction. Salicylaldehyde, pyridine-2-aldehyde, pyridine-4-aldehyde, and 4-hydroxy-3-methoxybenzylalcohol were not oxidized. No molecular hydrogen was detected in the gas phase. The oxidized aldehydes were not further degraded.     

Temperature and nutrient induced responses of Lake Fryxell sulfate-reducing prokaryotes and description of Desulfovibrio lacusfryxellense, sp. nov., a pervasive, cold-active, sulfate-reducing bacterium from Lake Fryxell, Antarctica

The effects of temperature and carbon substrate availability on the stimulation of sulfate reduction by indigenous populations of sulfate-reducing prokaryotes (SRP) in permanently ice-covered Lake Fryxell, Antarctica were investigated. Psychrophilic and halotolerant, lactate-degrading SRP showed significant metabolic activity throughout all sampled depths of the water column, suggesting that such organisms, possibly of marine origin, may be key contributors to carbon and sulfur cycling in Lake Fryxell. Planktonic and benthic strains of lactate-oxidizing sulfate-reducing bacteria (SRB) were isolated from samples of various depths of the anoxic water column and from surficial sediments. Phylogenetic analyses of 16S rRNA gene sequences placed the Fryxell sulfate-reducer (FSR) strains within the Deltaproteobacteria and showed them to be most closely related to the Arctic marine species of SRB Desulfovibrio frigidus and Desulfovibrio ferrireducens. Based on phylogenetic and phenotypic differences between the Antarctic FSR strains and related species of the genus Desulfovibrio, strain FSRs^T (=DSM 23315^T =ATCC BAA-2083^T) is proposed as the type strain of a novel species of cold-active SRB, Desulfovibrio lacusfryxellense, sp. nov.     

Impact of nitrate-mediated microbial control of souring in oil reservoirs on the extent of corrosion

The effect of microbial control of souring on the extent of corrosion was studied in a model system consisting of pure cultures of the nitrate-reducing, sulfide-oxidizing bacterium (NR-SOB) Thiomicrospira sp. strain CVO and the sulfate-reducing bacterium (SRB) Desulfovibrio sp. strain Lac6, as well as in an SRB consortium enriched from produced water from a Canadian oil reservoir. The average corrosion rate induced by the SRB consortium (1.4 g x m(-2) x day(-1)) was faster than that observed in the presence of strain Lac6 (0.2 g x m(-2) x day(-1)). Examination of the metallic coupons at the end of the tests indicated a uniform corrosion in both cases. Addition of CVO and 10 mM nitrate to a fully grown culture of Lac6 or the SRB consortium led to complete removal of sulfide from the system and a significant increase in the population of CVO, as determined by reverse sample genome probing. In the case of the SRB consortium addition of just nitrate (10 mM) had a similar effect. When grown in the absence of nitrate, the consortium was dominated by Desulfovibrio sp. strains Lac15 and Lac29, while growth in the presence of nitrate led to dominance of Desulfovibrio sp. strain Lac3. The addition of CVO and nitrate to the Lac6 culture or nitrate to the SRB consortium accelerated the average corrosion rate to 1.5 and 2.9 g x m(-2) x day(-1), respectively. Localized corrosion and the occurrence of pitting were apparent in both cases. Although the sulfide concentration (0.5-7 mM) had little effect on corrosion rates, a clear increase of the corrosion rate with increasing nitrate concentration was observed in experiments conducted with consortia enriched from produced water.     

Hydrogen-using bacteria in a methanogenic acetate enrichment culture

A rcher , D.B. 1984. Hydrogen-using bacteria in a methanogenic acetate enrichment culture. Journal of Applied Bacteriology 56 , 125–129.
In a study of the anaerobic utilization of acetate, an enrichment culture of sewage sludge organisms was initiated with calcium acetate as the sole carbon and energy source. A mixed bacterial population became established from which 14 anaerobic species were isolated. Two of the isolates were methanogenic bacteria but only one of these, Methanosarcina barkeri , utilised acetate as an energy source in axenic culture. The other methanogenic isolate, a Methanobacterium sp., utilised H₂/CO₂ but not acetate. A third methanogen, which was morphologically identical to Methanothrix soehngenii , was detected in the enrichment but was not obtained in monoculture. 2-Bromoethanesulphonate, a specific inhibitor of methanogenesis. completely inhibited the enrichment at a concentration of 10 μmol/1. Addition of H₂ formate or methanol to the enrichment did not affect the rate of methanogenesis. An H₂-utilizing Desulfovibrio sp. was also isolated from the enrichment.     

Identification of a bacterium that specifically catalyzes the reductive dechlorination of polychlorinated biphenyls with doubly flanked chlorines

A microorganism whose growth is linked to the dechlorination of polychlorinated biphenyls (PCBs) with doubly flanked chlorines was identified. Identification was made by reductive analysis of community 16S ribosomal DNA (rDNA) sequences from a culture enriched in the presence of 2,3,4,5-tetrachlorobiphenyl (2,3,4,5-CB), which was dechlorinated at the para position. Denaturing gradient gel electrophoresis (DGGE) analysis of total 16S rDNA extracted from the culture led to identification of three operational taxonomic units (OTUs 1, 2, and 3). OTU 1 was always detected when 2,3,4,5-CB or other congeners with doubly flanked chlorines were present and dechlorinated. Only OTUs 2 and 3 were detected in the absence of PCBs and when other PCBs (i.e., PCBs lacking doubly flanked chlorines) were not dechlorinated. Partial sequences of OTUs 2 and 3 exhibited 98.2% similarity to the sequence of "Desulfovibrio caledoniensis" (accession no. DCU53465). A sulfate-reducing vibrio isolated from the culture generated OTUs 2 and 3. This organism could not dechlorinate 2,3,4,5-CB. From these results we concluded that OTU 1 represents the dechlorinating bacterium growing in a coculture with a Desulfovibrio sp. The 16S rDNA sequence of OTU 1 is most similar to the 16S rDNA sequence of bacterium o-17 (89% similarity), an ortho-PCB-dechlorinating bacterium. The PCB dechlorinator, designated bacterium DF-1, reductively dechlorinates congeners with doubly flanked chlorines when it is supplied with formate or H(2)-CO(2) (80:20).     

Diversity and origin of Desulfovibrio species: phylogenetic definition of a family

The different nutritional properties of several Desulfovibrio desulfuricans strains suggest that either the strains are misclassified or there is a high degree of phenotypic diversity within the genus Desulfovibrio. The results of partial 16S rRNA and 23S rRNA sequence determinations demonstrated that Desulfovibrio desulfuricans ATCC 27774 and "Desulfovibrio multispirans" are closely related to the type strain (strain Essex 6) and that strains ATCC 7757, Norway 4, and El Agheila Z are not. Therefore, these latter three strains of Desulfovibrio desulfuricans are apparently misclassified. A comparative analysis of nearly complete 16S rRNA sequences in which we used a least-squares analysis method for evolutionary distances, an unweighted pair group method, a signature analysis method, and maximum parsimony was undertaken to further investigate the phylogeny of Desulfovibrio species. The species analyzed were resolved into two branches with origins deep within the delta subdivision of the purple photosynthetic bacteria. One branch contained five deep lineages, which were represented by (i) Desulfovibrio salexigens and Desulfovibrio desulfuricans El Agheila Z; (ii) Desulfovibrio africanus; (iii) Desulfovibrio desulfuricans ATCC 27774, Desulfomonas pigra, and Desulfovibrio vulgaris; (iv) Desulfovibrio gigas; and (v) Desulfomicrobium baculatus (Desulfovibrio baculatus) and Desulfovibrio desulfuricans Norway 4. A correlation between 16S rRNA sequence similarity and percentage of DNA relatedness showed that these five deep lineages are related at levels below the minimum genus level suggested by Johnson (in Bergey's Manual of Systematic Bacteriology, vol. 1, 1984). We propose that this branch should be grouped into a single family, the Desulfovibrionaceae. The other branch includes other genera of sulfate-reducing bacteria (e.g., Desulfobacter and Desulfococcus) and contains Desulfovibrio sapovorans and Desulfovibrio baarsii as separate, distantly related lineages.