pH值和产甲烷抑制剂对两相耦合系统污泥发酵定向产乙酸的影响

采用产氢产乙酸/同型产乙酸两相耦合工艺对剩余污泥进行了半连续式厌氧发酵,主要研究了pH值和产甲烷抑制剂2-bromoethanesulphonate(BES)对耦合系统定向产乙酸的影响.结果表明:碱性pH(pH=10.0)和添加BES都能促进A相乙酸的积累,提高乙酸的产率,同时碱性pH比添加BES更有利于污泥的水解.当...     

Granulomatous Propionibacterium acnes infection after trauma surgery

We report here a rare case of infection caused by Propionibacterium acnes following trauma surgery: a 36-year-old male, accident victim was admitted to the hospital because of polytrauma. He underwent a long-drawn-out surgical intervention and after a free-muscle transfer using the rectus femoris muscle, signs of inflammation were detected in the affected area. Microbiological examination of the wound revealed the presence of P. acnes as the only etiological agent of this infection. Adequate antibiotic treatment with penicillin had been started right after the positive microbiological result. Our data confirm the pathogenic potential of P. acnes in late post-surgical infections, and suggest a proper therapeutic approach with intravenous antibiotics and surgical removal of the infected tissue.     

Complete genome sequence of Bacteroides helcogenes type strain (P 36-108)

Bacteroides helcogenes Benno et al. 1983 is of interest because of its isolated phylogenetic location and, although it has been found in pig feces and is known to be pathogenic for pigs, occurrence of this bacterium is rare and it does not cause significant damage in intensive animal husbandry. The genome of B. helcogenes P 36-108(T) is already the fifth completed and published type strain genome from the genus Bacteroides in the family Bacteroidaceae. The 3,998,906 bp long genome with its 3,353 protein-coding and 83 RNA genes consists of one circular chromosome and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

Complete genome sequence of Mahella australiensis type strain (50-1 BON)

Mahella australiensis Bonilla Salinas et al. 2004 is the type species of the genus Mahella, which belongs to the family Thermoanaerobacteraceae. The species is of interest because it differs from other known anaerobic spore-forming bacteria in its G+C content, and in certain phenotypic traits, such as carbon source utilization and relationship to temperature. Moreover, it has been discussed that this species might be an indigenous member of petroleum and oil reservoirs. This is the first completed genome sequence of a member of the genus Mahella and the ninth completed type strain genome sequence from the family Thermoanaerobacteraceae. The 3,135,972 bp long genome with its 2,974 protein-coding and 59 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

Non-contiguous finished genome sequence of the opportunistic oral pathogen Prevotella multisaccharivorax type strain (PPPA20)

Prevotella multisaccharivorax Sakamoto et al. 2005 is a species of the large genus Prevotella, which belongs to the family Prevotellaceae. The species is of medical interest because its members are able to cause diseases in the human oral cavity such as periodontitis, root caries and others. Although 77 Prevotella genomes have already been sequenced or are targeted for sequencing, this is only the second completed genome sequence of a type strain of a species within the genus Prevotella to be published. The 3,388,644 bp long genome is assembled in three non-contiguous contigs, harbors 2,876 protein-coding and 75 RNA genes and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

Complete genome sequence of Rhodospirillum rubrum type strain (S1)

Rhodospirillum rubrum (Esmarch 1887) Molisch 1907 is the type species of the genus Rhodospirillum, which is the type genus of the family Rhodospirillaceae in the class Alphaproteobacteria. The species is of special interest because it is an anoxygenic phototroph that produces extracellular elemental sulfur (instead of oxygen) while harvesting light. It contains one of the most simple photosynthetic systems currently known, lacking light harvesting complex 2. Strain S1(T) can grow on carbon monoxide as sole energy source. With currently over 1,750 PubMed entries, R. rubrum is one of the most intensively studied microbial species, in particular for physiological and genetic studies. Next to R. centenum strain SW, the genome sequence of strain S1(T) is only the second genome of a member of the genus Rhodospirillum to be published, but the first type strain genome from the genus. The 4,352,825 bp long chromosome and 53,732 bp plasmid with a total of 3,850 protein-coding and 83 RNA genes were sequenced as part of the DOE Joint Genome Institute Program DOEM 2002.     

Complete genome sequence of the thermophilic sulfur-reducer Hippea maritima type strain (MH(2))

Hippea maritima (Miroshnichenko et al. 1999) is the type species of the genus Hippea, which belongs to the family Desulfurellaceae within the class Deltaproteobacteria. The anaerobic, moderately thermophilic marine sulfur-reducer was first isolated from shallow-water hot vents in Matipur Harbor, Papua New Guinea. H. maritima was of interest for genome sequencing because of its isolated phylogenetic location, as a distant next neighbor of the genus Desulfurella. Strain MH(2) (T) is the first type strain from the order Desulfurellales with a completely sequenced genome. The 1,694,430 bp long linear genome with its 1,723 protein-coding and 57 RNA genes consists of one circular chromosome and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

Anaerobic treatment of 2,4,6-trichlorophenol in an expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactor at 15 degrees C

Expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors were operated at 15 degrees C for the treatment of 2,4,6-trichlorophenol (TCP)-containing volatile fatty acid (VFA)-based wastewaters. The seed sludge used as inoculum for the control (no TCP) and test reactor was unexposed to chlorophenols (CPs) prior to the 425-day trial. TCP supplementation to the feed at 50 mg TCPl(-1) partially inhibited the anaerobic degradation of the VFA feed measured as COD removal efficiency. However, the withdrawal and subsequent application of stepwise increments to the TCP loading resulted in steady COD removal. Terminal restriction fragment length polymorphism analysis showed Methanosaeta-like Archaea in the control reactor over the experimental period. Different methanogenic populations were detected in the test reactor and responded to the changes in feed composition. Bacterial community analyses indicated changes in the community structure over time and suggested the presence of Campylobacter-like, Acidimicrobium-like and Heliophilum-like organisms in the samples. TCP mineralisation was by a reductive dechlorination pathway through 2,4-dichlorophenol (DCP) and 4-chlorophenol (4-CP) or 2-chlorophenol (2-CP). CP degradation rates in sludge granules from the lower chamber of the hybrid EGSB-AF reactor was in the order TCP > DCP > 4-CP > 2-CP. However, a biodegradability order of lower CPs > TCP was observed in fixed-film biomass taken from the upper reactor chamber, thus reflecting the role of this reactor section in the metabolism of residual lower CPs from the lower sludge-bed stage of operation.     

Propylphenols are metabolites in the anaerobic biodegradation of propylbenzene under iron-reducing conditions

The metabolism of monoaromatic hydrocarbons by an iron-reducing bacterial enrichment culture originating from diesel-contaminated groundwater was examined using d₇-propylbenzene as a model hydrocarbon. Sequence analysis of the 16S rDNA gene showed that the dominant part (10 of 10 clones) of the enrichment culture consisted of a bacterium closely related to clones found in benzene-contaminated groundwater and to the iron-reducing -proteobacterium, Rhodoferax ferrireducens (similarity values were 99.5% and 98.3%, respectively). In degradation studies conducted over 18 weeks, d₇-propylphenols were detected by gas chromatography–mass spectrometry (GC/MS) as intra-cellular metabolites concomitant with cell growth in the cultures. The amount of propylphenols increased during the exponential growth phase, and by the end of this phase 4 × 10^–14 moles of ferric iron were reduced and 3 × 10^–15 moles propylphenol produced for every cell formed. During the stationary growth phase the cell density was approximately 10⁷ ml^–1, with significantly correlated amounts of propylphenols. Succinate derivates of propylbenzene or phenylpropanol previously shown to be the initial metabolites in the anaerobic degradation of alkylbenzenes could not be identified. This study is the first to report that oxidation of propylbenzene to propylphenols can initiate anaerobic propylbenzene degradation and that iron-reducing bacteria are responsible for this process. In addition, the study shows the importance of taking account of the metabolites adhering to solid phases when determining the extent of biodegradation, so as not to underestimate the extent of the process.     

Anaerobic biodegradation of vegetable oil and its metabolic intermediates in oil-enriched freshwater sediments

Anaerobic biodegradation of vegetable oil in freshwater sediments is strongly inhibited by high concentrations of oil, but the presence of ferric hydroxide relieves the inhibition. The effect of ferric hydroxide is not due to physical or chemical interactions with long-chain fatty acids (LCFAs) that are produced as intermediates during metabolism of vegetable-oil triglycerides. The anaerobic biodegradation of canola oil and mixtures of acetic and oleic acids, two important intermediates of vegetable-oil metabolism, were investigated using sediments enriched on canola oil under methanogenic and iron-reducing conditions to determine whether the effect of ferric hydroxide has a biological basis. Sediments enriched under both conditions rapidly and completely converted canola oil to methane when the initial oil concentration was relatively low (1.9 g oil/kg sediments), but the biotransformation was strongly inhibited in sediments enriched under methanogenic conditions when the initial concentration was 19 g/kg (<30% of the oil-derived electron equivalents were transferred to methane in a 420-day incubation period). Sediments enriched under iron-reducing conditions, however, completely transformed canola oil to methane in about 250 days at this initial oil concentration. The anaerobic biotransformation of mixtures of acetate and oleic acid followed a similar pattern: the rate and extent of conversion of these electron-donor substrates to methane was always higher in sediments enriched under iron-reducing than under methanogenic conditions. These results suggest that enrichment on canola oil in the presence of ferric hydroxide selects a microbial community that is less sensitive to inhibition by LCFAs than the community that develops during enrichment under methanogenic conditions.