Enrichment of anaerobic methanotrophs in sulfate-reducing membrane bioreactors (original) (raw)
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Applied Microbiology and Biotechnology, 2010
Anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SR) is assumed to be a syntrophic process, in which methanotrophic archaea produce an interspecies electron carrier (IEC), which is subsequently utilized by sulfate-reducing bacteria. In this paper, six methanogenic substrates are tested as candidate-IECs by assessing their effect on AOM and SR by an anaerobic methanotrophic enrichment. The presence of acetate, formate or hydrogen enhanced SR, but did not inhibit AOM, nor did these substrates trigger methanogenesis. Carbon monoxide also enhanced SR but slightly inhibited AOM. Methanol did not enhance SR nor did it inhibit AOM, and methanethiol inhibited both SR and AOM completely. Subsequently, it was calculated at which candidate-IEC concentrations no more Gibbs free energy can be conserved from their production from methane at the applied conditions. These concentrations were at least 1,000 times lower can the final candidate-IEC concentration in the bulk liquid. Therefore, the tested candidate-IECs could not have been produced from methane during the incubations. Hence, acetate, formate, methanol, carbon monoxide, and hydrogen can be excluded as sole IEC in AOM coupled to SR. Methanethiol did inhibit AOM and can therefore not be excluded as IEC by this study.
Environmental Microbiology, 2009
Anaerobic oxidation of methane (AOM) is an important methane sink in the ocean but the microbes responsible for AOM are as yet resilient to cultivation. Here we describe the microbial analysis of an enrichment obtained in a novel submerged-membrane bioreactor system and capable of high-rate AOM (286 μmol gdry weight−1 day−1) coupled to sulfate reduction. By constructing a clone library with subsequent sequencing and fluorescent in situ hybridization, we showed that the responsible methanotrophs belong to the ANME-2a subgroup of anaerobic methanotrophic archaea, and that sulfate reduction is most likely performed by sulfate-reducing bacteria commonly found in association with other ANME-related archaea in marine sediments. Another relevant portion of the bacterial sequences can be clustered within the order of Flavobacteriales but their role remains to be elucidated. Fluorescent in situ hybridization analyses showed that the ANME-2a cells occur as single cells without close contact to the bacterial syntrophic partner. Incubation with 13C-labelled methane showed substantial incorporation of 13C label in the bacterial C16 fatty acids (bacterial; 20%, 44% and 49%) and in archaeal lipids, archaeol and hydroxyl-archaeol (21% and 20% respectively). The obtained data confirm that both archaea and bacteria are responsible for the anaerobic methane oxidation in a bioreactor enrichment inoculated with Eckernförde bay sediment.
Applied and Environmental Microbiology, 2005
The consumption of methane in anoxic marine sediments is a biogeochemical phenomenon mediated by two archaeal groups (ANME-1 and ANME-2) that exist syntrophically with sulfate-reducing bacteria. These anaerobic methanotrophs have yet to be recovered in pure culture, and key aspects of their ecology and physiology remain poorly understood. To characterize the growth and physiology of these anaerobic methanotrophs and the syntrophic sulfate-reducing bacteria, we incubated marine sediments using an anoxic, continuous-flow bioreactor during two experiments at different advective porewater flow rates. We examined the growth kinetics of anaerobic methanotrophs and Desulfosarcina-like sulfate-reducing bacteria using quantitative PCR as a proxy for cell counts, and measured methane oxidation rates using membrane-inlet mass spectrometry. Our data show that the specific growth rates of ANME-1 and ANME-2 archaea differed in response to porewater flow rates. ANME-2 methanotrophs had the highest rates in lower-flow regimes (mu(ANME-2) = 0.167 . week(-1)), whereas ANME-1 methanotrophs had the highest rates in higher-flow regimes (mu(ANME-1) = 0.218 . week(-1)). In both incubations, Desulfosarcina-like sulfate-reducing bacterial growth rates were approximately 0.3 . week(-1), and their growth dynamics suggested that sulfate-reducing bacterial growth might be facilitated by, but not dependent upon, an established anaerobic methanotrophic population. ANME-1 growth rates corroborate field observations that ANME-1 archaea flourish in higher-flow regimes. Our growth and methane oxidation rates jointly demonstrate that anaerobic methanotrophs are capable of attaining substantial growth over a range of environmental conditions used in these experiments, including relatively low methane partial pressures.
Applied and environmental microbiology, 2014
Anaerobic methane oxidizing communities of archaea (ANME) and sulfate reducing bacteria (SRB) grow slowly, which limits physiological studies. High methane partial pressure was previously successfully applied to stimulate growth, but it is not clear how different ANME subtypes and associated sulfate reducing bacteria (SRB) are affected by it. Here, we report growth of ANME/SRB in a membrane-capsule bioreactor inoculated with Eckernförde Bay sediment that combines high pressure incubation (10.1 MPa methane) and thorough mixing (100 rpm) with complete cell retention by a 0.2 μm membrane. Results were compared to previously obtained data from an ambient-pressure (0.101 MPa methane) bioreactor inoculated with the same sediment. Labelled-methane oxidation rates were not higher at 10.1 MPa, likely because measurements were done at ambient pressure. The subtype ANME-2a/b was abundant in both reactors, but subtype ANME-2c was only enriched at 10.1 MPa. SRB at 10.1 MPa mainly belonged to the...
Applied and Environmental Microbiology, 2003
Anaerobic methanotrophic archaea have recently been identified in anoxic marine sediments, but have not yet been recovered in pure culture. Physiological studies on freshly collected samples containing archaea and their sulfate-reducing syntrophic partners have been conducted, but sample availability and viability can limit the scope of these experiments. To better study microbial anaerobic methane oxidation, we developed a novel continuous-flow anaerobic methane incubation system (AMIS) that simulates the majority of in situ conditions and supports the metabolism and growth of anaerobic methanotrophic archaea. We incubated sediments collected from within and outside a methane cold seep in Monterey Canyon, Calif., for 24 weeks on the AMIS system. Anaerobic methane oxidation was measured in all sediments after incubation on AMIS, and quantitative molecular techniques verified the increases in methane-oxidizing archaeal populations in both seep and nonseep sediments. Our results demon...
Anaerobe, 2008
In this paper, the microbial characteristics of the granular sludge in the presence of oxygen (3.070.7 mg O 2 l À1 ) were analyzed using molecular biology techniques. The granules were provided by an upflow anaerobic sludge blanket (UASB) operated over 469 days and fed with synthetic substrate. Ethanol and sulfate were added to obtain different COD/SO 4 2À ratios (3.0, 2.0, and 1.6). The results of fluorescent in situ hybridization (FISH) analyses showed that archaeal cells, detected by the ARC915 probe, accounted for 77%, 84%, and 75% in the COD/SO 4 2À ratios (3.0, 2.0, and 1.6, respectively).
Applied Microbiology and Biotechnology, 2008
The microbial population structure and function of natural anaerobic communities maintained in lab-scale continuously stirred tank reactors at different lactate to sulfate ratios and in the absence of sulfate were analyzed using an integrated approach of molecular techniques and chemical analysis. The population structure, determined by denaturing gradient gel electrophoresis and by the use of oligonucleotide probes, was linked to the functional changes in the reactors. At the influent lactate to sulfate molar ratio of 0.35 mol mol −1 , i.e., electron donor limitation, lactate oxidation was mainly carried out by incompletely oxidizing sulfate-reducing bacteria, which formed 80-85% of the total bacterial population. Desulfomicrobium-and Desulfovibriolike species were the most abundant sulfate-reducing bacteria. Acetogens and methanogenic Archaea were mostly outcompeted, although less than 2% of an acetogenic population could still be observed at this limiting concentration of lactate. In the near absence of sulfate (i.e., at very high lactate/sulfate ratio), acetogens and methanogenic Archaea were the dominant microbial communities. Acetogenic bacteria represented by Dendrosporobacter quercicolus-like species formed more than 70% of the population, while methanogenic bacteria related to uncultured Archaea comprising about 10-15% of the microbial community. At an influent lactate to sulfate molar ratio of 2 mol mol −1 , i.e., under sulfate-limiting conditions, a different metabolic route was followed by the mixed anaerobic community. Apparently, lactate was fermented to acetate and propionate, while the majority of sulfidogenesis and methanogenesis were dependent on these fermentation products. This was consistent with the presence of significant levels (40-45% of total bacteria) of D. quercicolus-like heteroacetogens and a corresponding increase of propionate-oxidizing Desulfobulbus-like sulfate-reducing bacteria (20% of the total bacteria). Methanogenic Archaea accounted for 10% of the total microbial community.
Production of biogas: relationship between methanogenic and sulfate-reducing microorganisms
Open Life Sciences, 2017
The production of high-quality methane depends on many factors, including temperature, pH, substrate, composition and relationship of the microorganisms. The qualitative and quantitative composition of methanogenic and sulfate-reducing microorganisms and their relationship in the experimental bioreactors has never been studied. The aim of this research was to characterize, for the first time, the diversity of the methanogenic microorganisms and sulfate-reducing bacteria, and study their relationship and biogas production in experimental bioreactors. Amplification of 16S rRNA gene fragments was carried out. Purified amplicons were paired-end sequenced on an Illumina Mi-Seq platform. The dominant morphotypes of these microorganisms in the bioreactor were homologous (99%) by the sequences of 16S rRNA gene to theMethanosarcina,Thermogymnomonas,Methanoculleusgenera andArchaeondeposited in GenBank. Three dominant genera of sulfate-reducing bacteria,Desulfomicrobium,DesulfobulbusandDesulfo...
Applied and Environmental Microbiology, 1986
A variety of sulfur-containing compounds were investigated for use as medium reductants and sulfur sources for growth of four methanogenic bacteria. Sulfide (1 to 2 mM) served all methanogens investigated well. Methanococcus thermolithotrophicus and Methanobacterium thermoautotrophicum Marburg and AH grew well with S, s032-, or thiosulfate as the sole sulfur source. Only Methanococcus thermolithotrophicus was able to grow with s042as the sole sulfur source. 2-Mercaptoethanol at 20 mM was greatly inhibitory to growth of Methanococcus thermolithotrophicus on s042or s032and Methanobacterium thermoautotrophicum Marburg on s032but not to growth of strain AH on s032-. Sulfite was metabolized during growth by Methanococcus thermolithotrophicus. Sulfide was produced in cultures of Methanococcus thermolithotrophicus growing on s042-, s032-, thiosulfate, and So. Methanobacterium thermoautotrophicum Marburg was successfully grown in a 10-liter fermentor with S, s032-, or thiosulfate as the sole sulfur source.
Role of syntrophic microbial communities in high-rate methanogenic bioreactors
Water Science & Technology, 2012
Anaerobic purification is a cost-effective way to treat high strength industrial wastewater. Through anaerobic treatment of wastewaters energy is conserved as methane, and less sludge is produced. For high-rate methanogenesis compact syntrophic communities of fatty acid-degrading bacteria and methanogenic archaea are essential. Here, we describe the microbiology of syntrophic communities in methanogenic reactor sludges and provide information on which microbiological factors are essential to obtain high volumetric methane production rates. Fatty-acid degrading bacteria have been isolated from bioreactor sludges, but also from other sources such as freshwater sediments. Despite the important role that fatty acid-degrading bacteria play in high-rate methanogenic bioreactors, their relative numbers are generally low. This finding indicates that the microbial community composition can be further optimized to achieve even higher rates.