Biogas production from food waste via co-digestion and digestion- effects on performance and microbial ecology.

In this work, performance and microbial structure of a digestion (food waste-only) and a co-digestion process (mixture of cow manure and food waste) were studied at mesophilic (37 °C) and thermophilic (55 °C) temperatures. The highest methane yield (480 mL/g VS) was observed in the mesophilic digester (MDi) fed with food waste alone. The mesophilic co-digestion of food waste and manure (McoDi) yielded 26% more methane than the sum of individual digestions of manure and food waste. The main volatile fatty acid (VFA) in the mesophilic systems was acetate, averaging 93 and 172 mg/L for McoDi and MDi, respectively. Acetate (2150 mg/L) and propionate (833 mg/L) were the main VFAs in the thermophilic digester (TDi), while propionate (163 mg/L) was the major VFA in the thermophilic co-digester (TcoDi). The dominant bacteria in MDi was Chloroflexi (54%), while Firmicutes was dominant in McoDi (60%). For the mesophilic reactors, the dominant archaea was Methanosaeta in MDi, while Methanobacterium and Methanosaeta had similar abundance in McoDi. In the thermophilic systems, the dominant bacteria were Thermotogae, Firmicutes and Synergistetes in both digesters, however, the relative abundance of these phyla were different. For archaea, the genus Methanothermobacter were entirely dominant in both TDi and TcoDi.

Corrosion of carbon steel by bacteria from North Sea offshore seawater injection systems: laboratory investigation.

Influence of sulfidogenic bacteria, from a North Sea seawater injection system, on the corrosion of S235JR carbon steel was studied in a flow bioreactor; operating anaerobically for 100days with either inoculated or filtrated seawater. Deposits formed on steel placed in reactors contained magnesium and calcium minerals plus iron sulfide. The dominant biofilm-forming organism was an anaerobic bacterium, genus Caminicella, known to produce hydrogen sulfide and carbon dioxide. Open Circuit Potentials (OCP) of steel in the reactors was, for nearly the entire test duration, in the range -80045), suggested pitting on steel samples within the inoculated environment. However, the actual degree of corrosion could neither be directly correlated with the electrochemical data and nor with the steel corrosion in the filtrated seawater environment. Further laboratory tests are thought to clarify the noticed apparent discrepancies.

Colonization pattern of periodontal bacteria in Japanese children and their mothers.

BACKGROUND AND OBJECTIVE: The purpose of this study was to determine the time of infection by anaerobic gram-negative rods associated with periodontal disease, and to clarify their transmission from mother to child. MATERIAL AND METHODS: Seventy-eight Japanese children (including 10 siblings), aged from 3 to 9 years, and 68 mothers, were enrolled in this study. Colonization by 11 periodontal bacterial species was determined using polymerase chain reaction amplification of samples of subgingival plaque obtained from the children and their mothers. RESULTS: The detection rates of Porphyromonas gingivalis, Tannerella forsythensis and Treponema denticola increased in children after the age of 6 years. We found a high consistency in colonization by P. gingivalis, T. denticola, Prevotella intermedia and Prevotella nigrescens in 9 of the 10 siblings. The average number of bacterial species in plaque samples harboring Fusobacterium nucleatum and/or Fusobacterium periodonticum was significantly greater than in those without, in both children and mothers. Kappa statistical analysis revealed that the detection of Capnocytophaga gingivalis, Capnocytophaga ochracea, Campylobacter rectus and T. denticola in children was consistent with that in the mother. CONCLUSION: Periodontal bacterial colonization in Japanese children increased with age and was associated with F. nucleatum and/or periodonticum, and the bacterial flora in children was similar to that in their mothers.

Petrotoga halophila sp. nov., a thermophilic, moderately halophilic, fermentative bacterium isolated from an offshore oil well in Congo.

A novel thermophilic, moderately halophilic, rod-shaped bacterium, strain MET-B(T), with a sheath-like outer structure (toga) was isolated from an offshore oil-producing well in Congo, West Africa. Strain MET-B(T) was a Gram-negative bacterium with the ability to reduce elemental sulfur, but not sulfate, thiosulfate or sulfite into sulfide. The optimum growth conditions were 60 degrees C, pH 6.7-7.2 and 4-6 % NaCl. The DNA G+C content was 34.6 mol%. Strain MET-B(T) was phylogenetically related to members of the genus Petrotoga; Petrotoga miotherma, Petrotoga olearia and Petrotoga mexicana were the closest relatives, with type strains exhibiting more than 99 % identity in an analysis of small-subunit rRNA gene sequences. The values for DNA-DNA relatedness between the type strains of these three species and strain MET-B(T) were less than 42 %. As MET-B(T) was found to be genetically and physiologically different from other species of the genus Petrotoga, this strain is proposed as representing a novel species, for which the name Petrotoga halophila sp. nov. is proposed. The type strain is MET-B(T) (=DSM 16923(T)=CCUG 50214(T)).

Microbial biochemistry, physiology, and biotechnology of hyperthermophilic Thermotoga species.

High-throughput sequencing of microbial genomes has allowed the application of functional genomics methods to species lacking well-developed genetic systems. For the model hyperthermophile Thermotoga maritima, microarrays have been used in comparative genomic hybridization studies to investigate diversity among Thermotoga species. Transcriptional data have assisted in prediction of pathways for carbohydrate utilization, iron-sulfur cluster synthesis and repair, expolysaccharide formation, and quorum sensing. Structural genomics efforts aimed at the T. maritima proteome have yielded hundreds of high-resolution datasets and predicted functions for uncharacterized proteins. The information gained from genomics studies will be particularly useful for developing new biotechnology applications for T. maritima enzymes.

Mucispirillum schaedleri gen. nov., sp. nov., a spiral-shaped bacterium colonizing the mucus layer of the gastrointestinal tract of laboratory rodents.

The mammalian gastrointestinal tract is covered by a layer of mucus that can harbour a range of bacterial species specifically adapted to colonize this ecological niche. Examination of 110 bacterial isolates cultivated from the gastrointestinal tract of 23 mice revealed the presence of a subgroup of 30 isolates that did not correspond genetically with genera commonly associated with this site, i.e. members of the epsilon-Proteobacteria such as Helicobacter and Campylobacter species. Instead this group of isolates was found to lie within the phylum Deferribacteres, a completely distinct lineage in the domain Bacteria. There was a high level of consensus in results obtained from the phenotypic and genotypic characterization of a number of the isolates, which showed they were distinct from other members of the Deferribacteres. As such, they are proposed to constitute a new genus and species, Mucispirillum schaedleri gen. nov., sp. nov. These organisms are anaerobic, Gram-negative, spiral-shaped rods with bipolar flagella. The type strain is HRI I17(T) (= ATCC BAA-1009(T) = ACM 5223(T)).

Marinitoga hydrogenitolerans sp. nov., a novel member of the order Thermotogales isolated from a black smoker chimney on the Mid-Atlantic Ridge.

A novel, thermophilic, anaerobic bacterium that is able to tolerate hydrogen was isolated from a deep-sea hydrothermal chimney collected at the Rainbow field on the Mid-Atlantic Ridge. Cells were rod-shaped and surrounded by a sheath-like outer structure (toga); they were weakly motile by means of a polar flagellum. They appeared singly, in pairs or in short chains. They grew at 35-65 degrees C (optimum 60 degrees C), pH 4.5-8.5 (optimum pH 6.0) and 10-65 g sea salts l(-1) (optimum 30-40 g l(-1)). The isolate was organotrophic, and able to grow on various carbohydrates or complex proteinaceous substrates. Growth was not inhibited under 100 % hydrogen or in the presence of 2 % oxygen in the gas phase. The isolate reduces sulfur, although sulfur reduction is not required for growth. The fermentation products identified on glucose were acetate, ethanol, formate, hydrogen and CO(2). The G + C content of the genomic DNA was 28 +/- 1 mol%. Phylogenetic analysis of the 16S rRNA gene placed the strain within the genus Marinitoga, order Thermotogales, in the bacterial domain. On the basis of the 16S rRNA gene sequence comparisons and physiological characteristics, the isolate is considered to represent a novel species, for which the name Marinitoga hydrogenitolerans sp. nov. is proposed. The type strain is AT1271(T) (=DSM 16785(T) = JCM 12826(T)).

Attachment of oral gram-negative anaerobic rods to a smooth titanium surface: an electron microscopy study.

PURPOSE: Attachment of bacteria to titanium may differ not only between bacterial species but also between strains within a species. The aim of the present in vitro study was to examine differences in bacterial attachment using 4 gram-negative anaerobic species of bacteria that are considered potential periodontal pathogens. MATERIALS AND METHODS: The attachment of clinical and laboratory strains (n = 23) representing 2 Fusobacterium nucleatum subspecies, Porphyromonas gingivalis, and Prevotella intermedia to smooth, commercially pure titanium was examined using scanning electron microscopy. RESULTS: All bacterial strains were attached to the smooth titanium surface by their outer membrane. F nucleatum cells were poorly attached to the titanium, unlike P gingivalis or P intermedia cells, but only slight differences were observed in the quantity of attached cells between the strains within each bacterial group. DISCUSSION: In favorable conditions, some anaerobes can attach directly to an inert titanium surface. Microbial adhesion and subsequent colonization on the dental implant surface can lead to infection of the peri-implant tissue. CONCLUSION: The results indicated that the avidity of bacterial attachment to a smooth titanium surface varies between species of oral gram-negative anaerobes but not between strains.

An analysis of the proteomic profile for Thermoanaerobacter tengcongensis under optimal culture conditions.

The genome of Thermoanaerobacter tengcongensis is estimated to encode 2588 theoretical proteins. In this study, we have vitalized approximately 46% of the theoretical proteome experimentally using a proteomic strategy that combines three different methods, shotgun digestion plus high-performance liquid chromatography (HPLC) with ion-trap tandem mass spectrometry (shotgun-liquid chromatography (LC)/MS), one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) plus HPLC with ion-trap tandem mass spectrometry (one-dimensional electrophoresis (1DE)-LC/MS), and two-dimensional gel electrophoresis plus matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (2DE-MALDI-TOF-MS). Of the 1200 proteins identified, as few as 76 proteins were globally found by all three approaches, and notably, most of these proteins were in the soluble fraction. However, there were a number of unique proteins detected by one method only, suggesting that our strategy provides a means toward obtaining a comprehensive view of protein expression profile. Proteins from the major metabolic pathways are strongly represented on the map, and a number of these enzymes were identified by more than one proteomic method. Based upon the proteins identified in the present study, we are able to broaden the understanding of how T. tengcongensis survives under high temperature environment, whereas several of its properties can not be fully explained by genome data.

Algicidal activity and gliding motility of Saprospira sp. SS98-5.

A marine bacterium, Saprospira sp. SS98-5, which was isolated from Kagoshima Bay, Japan, was able to kill and lyse the cells of the diatom Chaetoceros ceratosporum. The multicellular filamentous cells of this bacterium captured the diatom cells, formed cell aggregates, and lysed them in an enriched sea water (ESS) liquid medium. Strain SS98-5 also formed plaques on double layer agar plates incorporating diatom cells. The diatom cell walls were partially degraded at the contact sites with the bacteria, the bacteria invaded from there into the diatom cells, and then the diatom cells were completely lysed. The strain possessed gliding motility and grew as spreading colonies on ESS agar plates containing lower concentrations of polypeptone (below 0.1%) while forming nonspreading colonies on ESS agar plates containing 0.5% polypeptone. Electron micrographs of ultrathin sections demonstrated that microtubule-like structures were observable only in gliding motile cells. Both the gliding motility and the microtubule-like structures were diminished by the addition of podophyllotoxin, an inhibitor of microtubule assembly, suggesting that the microtubule-like structures observed in these bacterial cells are related to their gliding motility.

Marinitoga piezophila sp. nov., a rod-shaped, thermo-piezophilic bacterium isolated under high hydrostatic pressure from a deep-sea hydrothermal vent.

A thermophilic, anaerobic, piezophilic, chemo-organotrophic sulfur-reducing bacterium, designated as KA3T, was isolated from a deep-sea hydrothermal chimney sample collected at a depth of 2630 m on the East-Pacific Rise (13 degrees N). When grown under elevated hydrostatic pressure, the cells are rod-shaped with a sheath-like outer structure, motile, have a mean length of 1-1.5 microm and stain Gram-negative. They appear singly or in short chains. When grown at lower, or atmospheric, pressures, the cells elongate and become twisted. Growth is enhanced by hydrostatic pressure; the optimal pressure for growth is 40 MPa (26 MPa pressure at sampling site). The temperature range for growth is 45-70 degrees C, the optimum being around 65 degrees C (doubling time is approximately 20 min at 40 MPa). Growth is observed from pH 5 to pH 8, the optimum being at pH 6. The salinity range for growth is 10-50 g NaCl l(-1), the optimum being at 30 g l(-1). The isolate is able to grow on a broad spectrum of carbohydrates or complex proteinaceous substrates, and growth is stimulated by L-cystine and elemental sulfur. The G+C content of the genomic DNA is 29 +/- 1 mol%. According to phylogenetic analysis of the 16S rDNA gene, the strain is placed within the order Thermotogales, in the bacterial domain. On the basis of 16S rDNA sequence comparisons and morphological, physiological and genotypic characteristics, it is proposed that the isolate be described as a novel species of the genus Marinitoga, with Marinitoga piezophila sp. nov. as the type species. The type strain is KA3T (= DSM 14283T = JCM 11233T).

Dialister pneumosintes, a new putative periodontal pathogen.

Recent studies have implicated Dialister pneumosintes as a candidate periodontal pathogen. This study determined the association of subgingival D. pneumosintes with demographic variables (age and gender) and the presence of subgingival periodontopathic Bacteroides forsythus and Porphyromonas gingivalis. Microbial identification by established PCR techniques was performed in samples from 149 periodontitis patients. Subgingival D. pneumosintes occurred with significantly higher prevalence in older individuals and was closely associated with subgingival B. forsythus. D. pneumosintes may play an important role in the microbial complex responsible for destructive periodontal disease.

Incidence of beta-lactamase production and antimicrobial susceptibility of anaerobic gram-negative rods isolated from pus specimens of orofacial odontogenic infections.

The incidence of beta-lactamase production in anaerobic gram-negative rods isolated from 93 pus specimens of orofacial odontogenic infections and the antimicrobial susceptibility of these isolates against 11 antibiotics were determined. A total of 191 anaerobic gram-negative rods were isolated from the specimens. Beta-lactamase was detected in 35.6% of the black-pigmented Prevotella and 31.9% of the nonpigmented Prevotella. However, no strains among the other species isolated produced beta-lactamase. Ampicillin, cefazolin and cefotaxime showed decreased activity as regards beta-lactamase-positive Prevotella strains, whereas the activity of ampicillin/sulbactam, cefmetazole, and imipenem continued to be effective against such strains. All tested beta-lactam antibiotics were effective against Porphyromonas and Fusobacterium. Erythromycin showed decreased activity against nonpigmented Prevotella and Fusobacterium. Clindamycin, minocycline and metronidazole were powerful antibiotics against which anaerobic gram-negative rods could be tested. The present study showed that beta-lactamase-positive strains were found more frequently in the Prevotella strains than in any of the other species of anaerobic gram-negative rods. The effectiveness of adding sulbactam to ampicillin was demonstrated, as well as the difference in cephalosporin activity against beta-lactamase-positive strains.

Thermohalobacter berrensis gen. nov., sp. nov., a thermophilic, strictly halophilic bacterium from a solar saltern.

A new thermophilic, strictly halophilic, anaerobic, non-sporulating rod-shaped bacterium, measuring 0.5 x 3.0-8.0 microns and designated strain CTT3T, was isolated from a solar saltern. Strain CTT3T stained Gram-negative, was motile by means of laterally inserted flagella, had a genome G + C content of 33 mol% and grew optimally at 65 degrees C and pH 7.0 with 5% NaCl. The strain also grew readily at 70 degrees C in the presence of 15% NaCl. Strain CTT3T fermented cellobiose, fructose, glucose, maltose, mannitol, mannose, sucrose, glycerol, N-acetylglucosamine, starch, pyruvate and bio-Trypticase. It produced acetate, ethanol, H2 and presumably CO2 from glucose. 16S rRNA gene sequence analysis indicated that it is a member of cluster XII of the Clostridiales and related genera of the subphylum of the Gram-positive bacteria containing genomes of low G + C content. Its phenotypic and phylogenetic characteristics clearly differentiated it from all other members of this cluster. Based on the findings it is proposed that strain CTT3T be designated as a new species of a new genus, Thermohalobacter berrensis gen. nov., sp. nov. The type strain is CTT3T (= CNCM 105955T).

Desulfovirga adipica gen. nov., sp. nov., an adipate-degrading, gram-negative, sulfate-reducing bacterium.

A novel, mesophilic, Gram-negative bacterium was isolated from an anaerobic digestor for municipal wastewater. The bacterium degraded adipate in the presence of sulfate, sulfite, thiosulfate and elemental sulfur. (E)-2-Hexenedioate accumulated transiently in the degradation of adipate. (E)-2-Hexenedioate, (E)-3-hexenedioate, pyruvate, lactate, C1-C12 straight-chain fatty acids and C2-C10 straight-chain primary alcohols were also utilized as electron donors. 3-Phenylpropionate was oxidized to benzoate. The G + C content of the DNA was 60 mol%. 16S rDNA sequence analysis revealed that the new isolate clustered with species of the genus Syntrophobacter and Desulforhabdus amnigenus. Strain TsuAS1T resembles Desulforhabdus amnigenus DSM 10338T with respect to the ability to utilize acetate as an electron donor and the inability to utilize propionate without sulfate in co-culture with Methanospirillum hungatei DSM 864. Strains TsuAS1T and DSM 10338T form a 'non-syntrophic subcluster' within the genus Syntrophobacter. Desulfovirga adipica gen. nov., sp. nov. is proposed for the newly isolated bacterium, with strain TsuAS1T (= DSM 12016T) as the type strain.

Orenia salinaria sp. nov., a fermentative bacterium isolated from anaerobic sediments of Mediterranean salterns.

A diverse range of fermentative bacteria have been isolated from the commercial salterns of Salin-de-Giraud (Camargue, France). One of these isolates, strain SG 3902T, has many of the morphological and physiological characteristics of the genus Orenia, as was confirmed by a phylogenetic study based on 16S rRNA gene sequencing. The closest species is Orenia marismortui, with a similarity of only 95.1%. However, strain SG 3902T, unlike O. marismortui, does not ferment mannose, glycogen or starch. The G + C contents of the DNA also differ significantly, being 29.6 mol% for O. marismortui and 33.7 mol% for strain SG 3902T. On the basis of these physiological and genetic differences, it is proposed that strain SG 3902T should be considered as a representative of a new species belonging to the genus Orenia, under the name Orenia salinaria sp. nov. The type strain is SG 3902T (= ATCC 700911).

Effect of rapid cooling and acidic pH on cellular homeostasis of Pectinatus frisingensis, a strictly anaerobic beer-spoilage bacterium.

Pectinatus frisingensis is a strictly anaerobic mesophilic bacterium involved in bottled beer spoilage. Cellular volume, adenylate energy charge, intracellular pH and intracellular potassium concentration measurements were performed in late exponential-phase cell suspensions placed in different physiological conditions, to evaluate the capability of this bacterium to maintain cellular homeostasis. The intracellular pH was calculated from the intracellular accumulation of a [carboxyl-14C]benzoic acid. Optimum physiological conditions were the presence of a carbon source and pH of 6.2, hostile conditions were a pH 4.5, absence of a carbon source, and rapid cooling treatment. The cell was able to maintain a higher intracellular pH than the external pH under all conditions. Intracellular volume was lower at pH 4.5 than at pH 6.2. A low net potassium efflux rate was routinely measured in starving cells, while glucose addition promoted immediate net potassium uptake from the medium. Cooling treatment resulted in sudden net potassium efflux from the cell, a decrease of the intracellular pH, and low modifications of the adenylate energy charge in metabolizing-glucose cell suspensions. Thus, cold treatment perturbs the P. frisingensis homeostasis but the bacteria were able to restore their homeostasis in the presence of a carbon source, and under warm conditions.

Sulfate-reducing bacteria in rice field soil and on rice roots.

Rice plants that were grown in flooded rice soil microcosms were examined for their ability to exhibit sulfate reducing activity. Washed excised rice roots showed sulfate reduction potential when incubated in anaerobic medium indicating the presence of sulfate-reducing bacteria. Rice plants, that were incubated in a double-chamber (phylloshpere and rhizosphere separated), showed potential sulfate reduction rates in the anoxic rhizosphere compartment. These rates decreased when oxygen was allowed to penetrate through the aerenchyma system of the plants into the anoxic root compartment, indicating that sulfate reducers on the roots were partially inhibited by oxygen or that sulfate was regenerated by oxidation of reduced S-compounds. The potential activity of sulfate reducers on rice roots was consistent with MPN enumerations showing that H2-utilizing sulfate-reducing bacteria were present in high numbers on the rhizoplane (4.1 x 10(7) g-1 root fresh weight) and in the adjacent rhizosperic soil (2.5 x 10(7) g-1 soil dry weight). Acetate-oxidizing sulfate reducers, on the other hand, showed highest numbers in the unplanted bulk soil (1.9 x 10(6) g-1 soil dry weight). Two sulfate reducing bacteria were isolated from the highest dilutions of the MPN series and were characterized physiologically and phylogenetically. Strain F1-7b which was isolated from the rhizoplane with H2 as electron donor was related to subgroup II of the family Desulfovibrionaceae. Strain EZ-2C2, isolated from the rhizoplane on acetate, grouped together with Desulforhabdus sp. and Syntrophobacter wolinii. Other strains of sulfate-reducing bacteria originated from bulk soil of rice soil microcosms and were isolated using different electron donors. From these isolates, strains R-AcA1, R-IbutA1, R-PimA1 and R-AcetonA170 were Gram-positive bacteria which were affiliated with the genus Desulfotomaculum. The other isolates were members of subgroup II of the Desulfovibrionaceae (R-SucA1 and R-LacA1), were related to Desulforhabdus sp. (strain BKA11), Desulfobulbus (R-PropA1), or culstered between Desulfobotulus sapovorans and Desulfosarcina variabilis (R-ButA1 and R-CaprA1).

Desulfobulbus rhabdoformis sp. nov., a sulfate reducer from a water-oil separation system.

A mesophilic, Gram-negative, rod-shaped, marine, propionate-oxidizing sulfate reducer (strain M16T) was isolated from a water-oil separation system on a North Sea oil platform. The optimum conditions for growth were 31 degrees C, pH 6.8-7.2 and 1.5-2.0% (w/v) NaCl and 0.1-0.3% (w/v) MgCl2.6H2O in the medium. The growth yield with sulfate was 4.6 g cell biomass (mol propionate oxidized)-1. Strain M16T is nutritionally related to members of the genus Desulfobulbus, but differs in that it has no vitamin requirement and is able to utilize fumarate and malate as carbon and energy sources. Hydrogenase activity measured as hydrogen uptake was mainly membrane-bound and varied with the growth substrate. Highest activity [28 mumol min-1 (mg protein)-1] was found in cells grown with hydrogen and lowest [50 nmol min-1 (mg protein)-1] in cells grown with propionate as electron donors for sulfate reduction. Desulforubidin, menaquinone-5(H2) and cytochromes of the c- and b-type were present. The fatty acid pattern was similar to that found for Desulfobulbus propionicus. The DNA base composition was 50.6 mol% G + C. Strain M16T is equidistantly related to D. propionicus and Desulfobulbus elongatus with 96.1% 16S rDNA similarity. On the basis of differences in genotypic, phenotypic and immunological characteristics, strain M16T (= DSM 8777T) is proposed as the type strain of a new species, Desulfobulbus rhabdoformis.

Desulfurella kamchatkensis sp. nov. and desulfurella propionica sp. nov., new sulfur-respiring thermophilic bacteria from Kamchatka thermal environments.

Two strains of moderately thermophilic bacteria, which reduce elemental sulfur to hydrogen sulfide, were isolated from volcanic sources in Kamchatka. Strain K-119T was obtained from a thermophilic microbial community associated with Thermothrix thiopara, and strain U-8T was isolated from a cyanobacterial mat inhabiting a sulfide-rich hot spring. Cells of both strains are short Gram-negative rods, motile with one polar flagellum (strain K-119T) or non-motile (strain U-8T). Both strains are obligate anaerobes, have temperature otima of 54-55 degrees C and pH optima of 6.9-7.2. Molecular hydrogen, acetate, fumarate, malate, pyruvate, lactate and long-chain saturated fatty acids served as growth substrates for both species; strain U-8T was also able to grow on propionate. All substrates were oxidized completely, H2S and CO2 being the only metabolic products. Elemental sulfur was obligately required for growth of strain K-119T, whereas strain U-8T was able to grow also with thiosulfate as electron acceptor and on pyruvate without an external electron acceptor. The DNA G + C contents of strains K-119T and U-8T were 31.6 and 32.2 mol%, respectively. Phenotypic features and the results of 16S rRNA sequencing indicate the affiliation of the new isolates to the genus Desulfurella. The DNA-DNA hybridization with Desulfurella acetivorans was 40% for strain K-119T and 55% for strain U-8T; the DNA-DNA hybridization between the new isolates was 32%. Based on the results of morphological, physiological and phylogenetic studies the following two new species are proposed: Desulfurella kamchatkensis sp. nov. with the type strain K-119T (= DSM 10409T) and Desulfurella propionica sp. nov. with the type strain U-8T (= DSM 10410T).