Desulfotomaculum Kuznetsovii Research Articles

Evaluation of a multi-step catalytic co-processing hydrotreatment for the production of renewable fuels using Category 3 animal fat and used cooking oils.

An alternative method for the production of renewable fuels from rendered animal fats (pretreated using methods 1-5 or method 7 as described in Annex IV of Commission Regulation (EC) No 2011/142) and used cooking oils, derived from Category 3 animal by-products, was assessed. The method is based on a catalytic co-processing hydrotreatment using a middle distillate followed by a stripping step. The materials must be submitted to a pressure of at least 60 bars and a temperature of at least 270°C for at least 4.7min. The application focuses on the demonstration of the level of reduction of spores from non-pathogenic spore-forming indicator bacterial species (Bacillus subtilis and Desulfotomaculum kuznetsovii), based on a non-systematic review of published data and additional extrapolation analyses. The EFSA BIOHAZ Panelconsiders that the application and supporting literature contain sufficient evidence that the proposed alternative method can achieve a reduction of at least 5 log10 in the spores of B. subtilis and a 12 log10 reduction in the spores of C. botulinum. The alternative method under evaluation is considered at least equivalent to the processing methods currently approved in the Commission Regulation (EU) No 2011/142.

The deep-subsurface sulfate reducer Desulfotomaculum kuznetsovii employs two methanol-degrading pathways

Methanol is generally metabolized through a pathway initiated by a cobalamine-containing methanol methyltransferase by anaerobic methylotrophs (such as methanogens and acetogens), or through oxidation to formaldehyde using a methanol dehydrogenase by aerobes. Methanol is an important substrate in deep-subsurface environments, where thermophilic sulfate-reducing bacteria of the genus Desulfotomaculum have key roles. Here, we study the methanol metabolism of Desulfotomaculum kuznetsovii strain 17T, isolated from a 3000-m deep geothermal water reservoir. We use proteomics to analyze cells grown with methanol and sulfate in the presence and absence of cobalt and vitamin B12. The results indicate the presence of two methanol-degrading pathways in D. kuznetsovii, a cobalt-dependent methanol methyltransferase and a cobalt-independent methanol dehydrogenase, which is further confirmed by stable isotope fractionation. This is the first report of a microorganism utilizing two distinct methanol conversion pathways. We hypothesize that this gives D. kuznetsovii a competitive advantage in its natural environment.

Multiple Amino Acid Sequence Alignment Nitrogenase Component 1: Insights into Phylogenetics and Structure-Function Relationships

Amino acid residues critical for a protein's structure-function are retained by natural selection and these residues are identified by the level of variance in co-aligned homologous protein sequences. The relevant residues in the nitrogen fixation Component 1 α- and β-subunits were identified by the alignment of 95 protein sequences. Proteins were included from species encompassing multiple microbial phyla and diverse ecological niches as well as the nitrogen fixation genotypes, anf, nif, and vnf, which encode proteins associated with cofactors differing at one metal site. After adjusting for differences in sequence length, insertions, and deletions, the remaining >85% of the sequence co-aligned the subunits from the three genotypes. Six Groups, designated Anf, Vnf , and Nif I-IV, were assigned based upon genetic origin, sequence adjustments, and conserved residues. Both subunits subdivided into the same groups. Invariant and single variant residues were identified and were defined as “core” for nitrogenase function. Three species in Group Nif-III, Candidatus Desulforudis audaxviator, Desulfotomaculum kuznetsovii, and Thermodesulfatator indicus, were found to have a seleno-cysteine that replaces one cysteinyl ligand of the 8Fe:7S, P-cluster. Subsets of invariant residues, limited to individual groups, were identified; these unique residues help identify the gene of origin (anf, nif, or vnf) yet should not be considered diagnostic of the metal content of associated cofactors. Fourteen of the 19 residues that compose the cofactor pocket are invariant or single variant; the other five residues are highly variable but do not correlate with the putative metal content of the cofactor. The variable residues are clustered on one side of the cofactor, away from other functional centers in the three dimensional structure. Many of the invariant and single variant residues were not previously recognized as potentially critical and their identification provides the bases for new analyses of the three-dimensional structure and for mutagenesis studies.

Genome analysis of Desulfotomaculum kuznetsovii strain 17(T) reveals a physiological similarity with Pelotomaculum thermopropionicum strain SI(T).

Desulfotomaculum kuznetsovii is a moderately thermophilic member of the polyphyletic spore-forming genus Desulfotomaculum in the family Peptococcaceae. This species is of interest because it originates from deep subsurface thermal mineral water at a depth of about 3,000 m. D. kuznetsovii is a rather versatile bacterium as it can grow with a large variety of organic substrates, including short-chain and long-chain fatty acids, which are degraded completely to carbon dioxide coupled to the reduction of sulfate. It can grow methylotrophically with methanol and sulfate and autotrophically with H2 + CO2 and sulfate. For growth it does not require any vitamins. Here, we describe the features of D. kuznetsovii together with the genome sequence and annotation. The chromosome has 3,601,386 bp organized in one contig. A total of 3,567 candidate protein-encoding genes and 58 RNA genes were identified. Genes of the acetyl-CoA pathway, possibly involved in heterotrophic growth with acetate and methanol, and in CO2 fixation during autotrophic growth are present. Genomic comparison revealed that D. kuznetsovii shows a high similarity with Pelotomaculum thermopropionicum. Genes involved in propionate metabolism of these two strains show a strong similarity. However, main differences are found in genes involved in the electron acceptor metabolism.

Molecular characterization and corrosion behavior of thermophilic (55 °C) SRB Desulfotomaculum kuznetsovii isolated from cooling tower in petroleum refinery

AbstractDesulfotomaculum kuznetsovii (D. kuznetsovii), a thermophilic sulfate‐reducing bacterium (SRB), was identified in a cooling tower of a petroleum refinery by 16S rRNA gene sequencing and its functional gene encoding dissimilatory sulfite reductase (dsrAB). The thermophilic sulfate‐reducing bacterial species have been reported for the first time in the cooling towers of an Indian petroleum refinery. The protein coded by dsrAB gene was cloned, expressed, and identified using recombinant DNA technology. Weight loss method, electrochemical and surface analysis showed the corrosion behavior of the isolate. In the presence of D. kuznetsovii, the corrosion rate was higher when compared to control at 55 °C. It suppresses the anodic reaction and enhances the cathodic reaction by the production of organic complex and iron sulfide, respectively. Numerous pitting were noticed on mild steel which is due to the presence of D. kuznetsovii and its role in the corrosion process has been discussed.

Carbon monoxide conversion by thermophilic sulfate-reducing bacteria in pure culture and in co-culture with Carboxydothermus hydrogenoformans

Biological sulfate (SO(4)) reduction with carbon monoxide (CO) as electron donor was investigated. Four thermophilic SO(4)-reducing bacteria, Desulfotomaculum thermoacetoxidans (DSM 5813), Thermodesulfovibrio yellowstonii (ATCC 51303), Desulfotomaculum kuznetsovii (DSM 6115; VKM B-1805), and Desulfotomaculum thermobenzoicum subsp. thermosyntrophicum (DSM 14055), were studied in pure culture and in co-culture with the thermophilic carboxydotrophic bacterium Carboxydothermus hydrogenoformans (DSM 6008). D. thermoacetoxidans and T. yellowstonii were extremely sensitive to CO: their growth on pyruvate was completely inhibited at CO concentrations above 2% in the gas phase. D. kuznetsovii and D. thermobenzoicum subsp. thermosyntrophicum were less sensitive to CO. In pure culture, D. kuznetsovii and D. thermobenzoicum subsp. thermosyntrophicum were able to grow on CO as the only electron donor and, in particular in the presence of hydrogen/carbon dioxide, at CO concentrations as high as 50-70%. The latter SO(4) reducers coupled CO oxidation to SO(4) reduction, but a large part of the CO was converted to acetate. In co-culture with C. hydrogenoformans, D. kuznetsovii and D. thermobenzoicum subsp. thermosyntrophicum could even grow with 100% CO (P(CO) = 120 kPa).

Methanol utilization in defined mixed cultures of thermophilic anaerobes in the presence of sulfate

We studied thermophilic sulfate reduction with methanol as electron donor in continuous cultures. Mixed cultures of selected microorganisms were used, representing different methanol degrading pathways followed by various trophic groups of microorganisms. Our results show that direct competition for methanol between a homoacetogen, Moorella thermoautotrophica, and a sulfate reducer, Desulfotomaculum kuznetsovii, is in favour of the sulfate reducer due to its affinity for methanol. Methanogenesis as a result of interspecies hydrogen transfer between D. kuznetsovii and a hydrogen-consuming methanogenic archaeon, Methanothermobacter thermoautotrophicus occurred only below 5 mM total sulfide. A similar result was obtained when M. thermoautotrophica was grown on methanol in the presence of Mb. thermoautotrophicus. Interestingly, D. kuznetsovii could coexist with a non-methanol-utilizing sulfate reducer ( Thermodesulfovibrio species). Our data show that it is possible to maintain a dominant sulfate-reducing process with methanol as electron donor at 60 °C in mixed continuous cultures.

Heterogeneity of the nucleotide sequences of the 16S rRNA genes of the type strain of Desulfotomaculum kuznetsovii

Two copies of the 16S rRNA gene, rrnAand rrnB, of the type strain 17Tof the thermophilic sulfate-reducing bacterium Desulfotomaculum kuznetsoviiwere cloned and completely sequenced. The comparison of the determined sequences revealed considerable heterogeneity (8.3%) of the two genes, rrnAand rrnB.The main differences were associated with superlong inserts located in the variable 5"- and 3"-terminal regions of the 16S rRNA genes. Comparative analysis that involved analogous genes from the phylogenetically closest representatives of the genus Desulfotomaculumshowed that disregard of the heterogeneity of the two gene copies distorts the position of the bacterium studied in the phylogenetic tree.

Phylogenetic analysis of the genus Desulfotomaculum: evidence for the misclassification of Desulfotomaculum guttoideum and description of Desulfotomaculum orientis as Desulfosporosinus orientis gen. nov., comb. nov.

Almost complete 16S ribosomal DNA (rDNA) sequences were determined for the type strains of nine species belonging to the genus Desulfotomaculum and for seven strains described as strains of this genus. The sequences were compared with previously published 16S rDNA and rRNA sequences of the type strains of the other species of the genus. The majority of the species form a phylogenetically coherent cluster within the Clostridium-Bacillus subphylum of gram-positive bacteria. The cluster consists of phylogenetically well-separated lineages containing (i) Desulfotomaculum nigrificans, Desulfotomaculum aeronauticum, and Desulfotomaculum ruminis, (ii) Desulfotomaculum geothermicum, Desulfotomaculum thermosapovorans, and Desulfotomaculum sapomandens, (iii) Desulfotomaculum kuznetsovii, Desulfotomaculum australicum, and Desulfotomaculum thermocisternum, (iv) Desulfotomaculum thermobenzoicum and Desulfotomaculum thermoacetoxidans, and (v) Desulfotomaculum acetoxidans. Some as-yet-undescribed Desulfotomaculum strains are phylogenetically well-separated from strains of the described species. Desulfotomaculum guttoideum shares extremely high 16S rDNA similarity with certain Clostridium species (e.g., Clostridium sphenoides and Clostridium celerecrescens) and is most likely a misidentified species. Desulfotomaculum orientis represents a new genus which branches most closely to the genus Desulfitobacterium. The name Desulfosporosinus orientis gen. nov., comb. nov., is proposed for this taxon.