Metabolic Synergy between Human Symbionts Bacteroides and Methanobrevibacter

Trophic interactions between microbes are postulated to determine whether a host microbiome is healthy or causes predisposition to disease. Two abundant taxa, the Gram-negative heterotrophic bacterium Bacteroides thetaiotaomicron and the methanogenic archaeon Methanobrevibacter smithii, are proposed to have a synergistic metabolic relationship. Both organisms play vital roles in human gut health; B. thetaiotaomicron assists the host by fermenting dietary polysaccharides, whereas M. smithii consumes end-stage fermentation products and is hypothesized to relieve feedback inhibition of upstream microbes such as B. thetaiotaomicron. To study their metabolic interactions, we defined and optimized a coculture system and used software testing techniques to analyze growth under a range of conditions representing the nutrient environment of the host. We verify that B. thetaiotaomicron fermentation products are sufficient for M. smithii growth and that accumulation of fermentation products alters secretion of metabolites by B. thetaiotaomicron to benefit M. smithii. Studies suggest that B. thetaiotaomicron metabolic efficiency is greater in the absence of fermentation products or in the presence of M. smithii. Under certain conditions, B. thetaiotaomicron and M. smithii form interspecies granules consistent with behavior observed for syntrophic partnerships between microbes in soil or sediment enrichments and anaerobic digesters. Furthermore, when vitamin B12, hematin, and hydrogen gas are abundant, coculture growth is greater than the sum of growth observed for monocultures, suggesting that both organisms benefit from a synergistic mutual metabolic relationship. IMPORTANCE The human gut functions through a complex system of interactions between the host human tissue and the microbes which inhabit it. These diverse interactions are difficult to model or examine under controlled laboratory conditions. We studied the interactions between two dominant human gut microbes, B. thetaiotaomicron and M. smithii, using a seven-component culturing approach that allows the systematic examination of the metabolic complexity of this binary microbial system. By combining high-throughput methods with machine learning techniques, we were able to investigate the interactions between two dominant genera of the gut microbiome in a wide variety of environmental conditions. Our approach can be broadly applied to studying microbial interactions and may be extended to evaluate and curate computational metabolic models. The software tools developed for this study are available as user-friendly tutorials in the Department of Energy KBase.

SepF is the FtsZ anchor in archaea, with features of an ancestral cell division system

Most archaea divide by binary fission using an FtsZ-based system similar to that of bacteria, but they lack many of the divisome components described in model bacterial organisms. Notably, among the multiple factors that tether FtsZ to the membrane during bacterial cell constriction, archaea only possess SepF-like homologs. Here, we combine structural, cellular, and evolutionary analyses to demonstrate that SepF is the FtsZ anchor in the human-associated archaeon Methanobrevibacter smithii. 3D super-resolution microscopy and quantitative analysis of immunolabeled cells show that SepF transiently co-localizes with FtsZ at the septum and possibly primes the future division plane. M. smithii SepF binds to membranes and to FtsZ, inducing filament bundling. High-resolution crystal structures of archaeal SepF alone and in complex with the FtsZ C-terminal domain (FtsZCTD) reveal that SepF forms a dimer with a homodimerization interface driving a binding mode that is different from that previously reported in bacteria. Phylogenetic analyses of SepF and FtsZ from bacteria and archaea indicate that the two proteins may date back to the Last Universal Common Ancestor (LUCA), and we speculate that the archaeal mode of SepF/FtsZ interaction might reflect an ancestral feature. Our results provide insights into the mechanisms of archaeal cell division and pave the way for a better understanding of the processes underlying the divide between the two prokaryotic domains.

Detoxification of Ciprofloxacin in an Anaerobic Bioprocess Supplemented with Magnetic Carbon Nanotubes: Contribution of Adsorption and Biodegradation Mechanisms

In anaerobic bioreactors, the electrons produced during the oxidation of organic matter can potentially be used for the biological reduction of pharmaceuticals in wastewaters. Common electron transfer limitations benefit from the acceleration of reactions through utilization of redox mediators (RM). This work explores the potential of carbon nanomaterials (CNM) as RM on the anaerobic removal of ciprofloxacin (CIP). Pristine and tailored carbon nanotubes (CNT) were first tested for chemical reduction of CIP, and pristine CNT was found as the best material, so it was further utilized in biological anaerobic assays with anaerobic granular sludge (GS). In addition, magnetic CNT were prepared and also tested in biological assays, as they are easier to be recovered and reused. In biological tests with CNM, approximately 99% CIP removal was achieved, and the reaction rates increased ≈1.5-fold relatively to the control without CNM. In these experiments, CIP adsorption onto GS and CNM was above 90%. Despite, after applying three successive cycles of CIP addition, the catalytic properties of magnetic CNT were maintained while adsorption decreased to 29 ± 3.2%, as the result of CNM overload by CIP. The results suggest the combined occurrence of different mechanisms for CIP removal: adsorption on GS and/or CNM, and biological reduction or oxidation, which can be accelerated by the presence of CNM. After biological treatment with CNM, toxicity towards Vibrio fischeri was evaluated, resulting in ≈ 46% detoxification of CIP solution, showing the advantages of combining biological treatment with CNM for CIP removal.

Effects of the particle of ground alfalfa hay on the growth performance, methane production and archaeal populations of rabbits

The world's annual output of rabbits is over 1.2 billion, therefore this sector is also one of the sources of greenhouse gases in livestock production. One hundred-twenty New Zealand rabbits were allocated into four treatments, five replicates in each treatment and six rabbits in each replicate to examine the effect of grinding alfalfa hay to different sizes on growth performance, methane production and cecal archaeal populations. The particle sizes of the alfalfa meal in the four treatment diets were 2500, 1000, 100 and 10 μm, while the other ingredients were ground through a 2.5 mm sieve. The average daily gain (ADG) and average daily feed intake (ADFI) increased (P<0.001) as the particle size decreased, but the feed conversion ratio (FCR) was not affected (P = 0.305). The digestibility of neutral detergent fiber (NDF) (P = 0.006) and acid detergent fiber (ADF) (P<0.006) increased while the greatest digestibility of crude protein (CP) was obtained in 1000 um group (P = 0.015). The rabbits produced more methane (CH4, L/kgBM0.75/d) with decreasing alfalfa particle size (P<0.001). The molar proportion of acetic acid and propionic acid decreased (P<0.001) at the cost of butyric acid (P<0.001). The greatest villus height:crypt depth ratio were obtained in 1000 μm group, and the decrease in the alfalfa hay particle size decreased the jejunum and ilem villus height:crypt depth ratio (P<0.05). The gastric muscular and mucosal thickness decreased with decreasing alfalfa particle size (P<0.05). Archaea diversity decreased with decreasing alfalfa particle size, and the relative abundance of genus Methanobrevibacter increased (P<0.001) while the genus Methanosphaera decreased (P<0.001). It is concluded that a finer particle size favors the growth of genus Methanobrevibacter, which produces more methane but promotes the growth performance of rabbits.

Development of a Modified-Release Formulation of Lovastatin Targeted to Intestinal Methanogens Implicated in Irritable Bowel Syndrome With Constipation

There is growing evidence that methane production, predominantly by Methanobrevibacter smithii, in the intestines is a cause of constipation, pain, and bloating in irritable bowel syndrome with constipation (IBS-C). M smithii resides primarily in the large intestine but can also colonize the small intestine. In vitro studies found that the prodrug lactone form of lovastatin, found in cholesterol-lowering drugs, inhibited methane production in stool samples from patients with IBS-C. However, the cholesterol-lowering lovastatin β-hydroxyacid was ineffective at inhibiting methane production in this system. A considerable amount of lovastatin is converted to hydroxyacid in the stomach and is absorbed. It was hypothesized that galenic innovations could protect lovastatin from the stomach and allow release in 2 strategic locations, the duodenum and the ileocecal region, to reach M smithii. The desired release profile was achieved by developing an oral dosage form containing lovastatin and coated with 2 different enteric polymers that enabled a pH-dependent "dual pulse" drug release. Combinations of the 2 coated tablets were encapsulated together to deliver the desired amount of lovastatin to the targeted intestinal locations. The capsules have been tested in vitro and in vivo and show promise in treating IBS-C.

Dietary pea fiber increases diversity of colonic methanogens of pigs with a shift from Methanobrevibacter to Methanomassiliicoccus-like genus and change in numbers of three hydrogenotrophs

BACKGROUND

Pea fiber (PF) is a potential fibrous supplement in swine production. The influence of dietary PF on microbial community in the colon of pigs remains largely unexplored. Methanogens in the hindgut of monogastric animals play important roles in degradation of dietary fibers and efficient removal of microbial metabolic end product H2. Understanding the impact of dietary PF on the structure of colonic methanogens may help understand the mechanisms of microbe-mediated physiological functions of PF. This study investigated the influence of PF on the diversity and quantity and/or activity of colonic methanongens of piglets and finishing pigs. Four archaeal 16S rRNA clone libraries were constructed for piglets and finishers fed with control (Piglet-C and Finisher-C) or PF diet (Piglet-P and Finisher-P).

RESULTS

There were 195, 190, 194 and 196 clones obtained from the library Piglet-C, Piglet-P, Finisher-C and Finisher-P, respectively, with corresponding 12, 11, 11 and 16 OTUs (operational taxonomic units). Significant differences of Shannon Index among the four libraries were found (P < 0.05). Libshuff analysis showed that the archaeal community structure among the four libraries were significantly different (P < 0.0001). The predominant methanogens shifted from Methanobrevibacter to Methanobrevibacter and Methanomassiliicoccus-like genus as a result of dietary PF. Supplementation of PF significantly increased the copy numbers of mcrA and dsrA genes (P < 0.05).

CONCLUSIONS

Alteration of methanogenic community structure may lead to functional transition from utilization of H2/CO2 to employment of both H2/CO2 and methanol/CO2. Quantification of three functional genes (mcrA, dsrA and fhs) of methanogens, sulfate-reducing bacteria (SRB) and acetogens revealed that dietary PF also increased the activity of methanogens and SRB,probably associated with increased proportion of Methanomassiliicoccus luminyensis-species. Further study is required to examine the interaction between specific methanogens and SRB during fermentation of dietary PF.

Illumina MiSeq Phylogenetic Amplicon Sequencing Shows a Large Reduction of an Uncharacterised Succinivibrionaceae and an Increase of the Methanobrevibacter gottschalkii Clade in Feed Restricted Cattle

Periodic feed restriction is used in cattle production to reduce feed costs. When normal feed levels are resumed, cattle catch up to a normal weight by an acceleration of normal growth rate, known as compensatory growth, which is not yet fully understood. Illumina Miseq Phylogenetic marker amplicon sequencing of DNA extracted from rumen contents of 55 bulls showed that restriction of feed (70% concentrate, 30% grass silage) for 125 days, to levels that caused a 60% reduction of growth rate, resulted in a large increase of relative abundance of Methanobrevibacter gottschalkii clade (designated as OTU-M7), and a large reduction of an uncharacterised Succinivibrionaceae species (designated as OTU-S3004). There was a strong negative Spearman correlation (ρ = -0.72, P = <1x10^-20) between relative abundances of OTU-3004 and OTU-M7 in the liquid rumen fraction. There was also a significant increase in acetate:propionate ratio (A:P) in feed restricted animals that showed a negative Spearman correlation (ρ = -0.69, P = <1x10^-20) with the relative abundance of OTU-S3004 in the rumen liquid fraction but not the solid fraction, and a strong positive Spearman correlation with OTU-M7 in the rumen liquid (ρ = 0.74, P = <1x10^-20) and solid (ρ = 0.69, P = <1x10^-20) fractions. Reduced A:P ratios in the rumen are associated with increased feed efficiency and reduced production of methane which has a global warming potential (GWP 100 years) of 28. Succinivibrionaceae growth in the rumen was previously suggested to reduce methane emissions as some members of this family utilise hydrogen, which is also utilised by methanogens for methanogenesis, to generate succinate which is converted to propionate. Relative abundance of OTU-S3004 showed a positive Spearman correlation with propionate (ρ = 0.41, P = <0.01) but not acetate in the liquid rumen fraction.

Inhibition of methyl-CoM Reductase from Methanobrevibacter ruminantium by 2-bromoethanesulfonate

Cattle husbandry is a major contributor to atmospheric methane, which is considered as an important greenhouse gas. Moreover, the generation of methane in the intestine of domestic ruminants by methanogenic bacteria is a drag on feed efficacy. Studies on methanogenesis have typically implied model organisms that are, however, not relevant in the ruminant gut. This paper shows that methyl-CoM reductase catalyzing the final step of methanogenesis in Methanobrevibacter ruminantium, a major participant in methane production by cattle, is inhibited by 2-bromoethanesulfonate, a compound often used as a model in animal agriculture, with an apparent IC50 of 0.4 ± 0.04 μM.

Sewage pollution in urban stormwater runoff as evident from the widespread presence of multiple microbial and chemical source tracking markers

The concurrence of human sewage contamination in urban stormwater runoff (n=23) from six urban catchments across Australia was assessed by using both microbial source tracking (MST) and chemical source tracking (CST) markers. Out of 23 stormwater samples human adenovirus (HAv), human polyomavirus (HPv) and the sewage-associated markers; Methanobrevibacter smithii nifH and Bacteroides HF183 were detected in 91%, 56%, 43% and 96% of samples, respectively. Similarly, CST markers paracetamol (87%), salicylic acid (78%) acesulfame (96%) and caffeine (91%) were frequently detected. Twenty one samples (91%) were positive for six to eight sewage related MST and CST markers and remaining two samples were positive for five and four markers, respectively. A very good consensus (>91%) observed between the concurrence of the HF183, HAv, acesulfame and caffeine suggests good predictability of the presence of HAv in samples positive for one of the three markers. High prevalence of HAv (91%) also suggests that other enteric viruses may also be present in the stormwater samples which may pose significant health risks. This study underscores the benefits of employing a set of MST and CST markers which could include monitoring for HF183, adenovirus, caffeine and paracetamol to accurately detect human sewage contamination along with credible information on the presence of human enteric viruses, which could be used for more reliable public health risk assessments. Based on the results obtained in this study, it is recommended that some degree of treatment of captured stormwater would be required if it were to be used for non-potable purposes.

HuBac and nifH source tracking markers display a relationship to land use but not rainfall

Identification of the source of fecal pollution is becoming a priority for states and territories in the U.S. in order to meet water quality standards and to develop and implement total maximum daily loads. The goal of this research was to relate microbial source tracking (MST) assay concentrations to land use and levels of impervious surfaces in order to gauge how increasing development is associated with human fecal contamination in inland watersheds. The concentrations of two proposed MST markers, targeting nifH of Methanobrevibacter smithii and HuBac of Bacteroides sp., were positively correlated with increasing anthropogenic development and impervious surfaces. Higher concentrations of these MST markers in more urbanized watersheds suggest that increasing development negatively affects water quality. Neither MST marker concentration was correlated with antecedent rainfall levels, and detection of markers did not differ between dry weather and rain events. Water samples were also analyzed for norovirus and enterovirus, but these enteric viruses were rarely detected. These MST results differ from previous studies that have found correlations between traditional fecal indicator bacteria (FIB) and antecedent rainfall. This difference suggests that the MST markers used in this study may be more specific for recent, land-based contamination events as opposed to resuspension of particle-associated organisms in waterways. HuBac was detected in 98% of samples, correlating with fecal coliform and Escherichia coli concentrations. The ubiquity of the HuBac marker in our samples suggests that this marker does not provide sufficiently different or additional information than FIB, and it is likely this marker was amplifying non-human targets. The nifH marker was detected in 30% of samples. Less than half of the nifH-positive samples contained levels of fecal coliforms or E. coli above regulatory thresholds, suggesting that nifH would be more useful when utilized simultaneously with FIB than in a tiered monitoring strategy. The results of this research suggests that land use factors play an important role in characterizing and mitigating fecal contamination in watersheds.

The genome sequence of the rumen methanogen Methanobrevibacter ruminantium reveals new possibilities for controlling ruminant methane emissions

BACKGROUND

Methane (CH(4)) is a potent greenhouse gas (GHG), having a global warming potential 21 times that of carbon dioxide (CO(2)). Methane emissions from agriculture represent around 40% of the emissions produced by human-related activities, the single largest source being enteric fermentation, mainly in ruminant livestock. Technologies to reduce these emissions are lacking. Ruminant methane is formed by the action of methanogenic archaea typified by Methanobrevibacter ruminantium, which is present in ruminants fed a wide variety of diets worldwide. To gain more insight into the lifestyle of a rumen methanogen, and to identify genes and proteins that can be targeted to reduce methane production, we have sequenced the 2.93 Mb genome of M. ruminantium M1, the first rumen methanogen genome to be completed.

METHODOLOGY/PRINCIPAL FINDINGS

The M1 genome was sequenced, annotated and subjected to comparative genomic and metabolic pathway analyses. Conserved and methanogen-specific gene sets suitable as targets for vaccine development or chemogenomic-based inhibition of rumen methanogens were identified. The feasibility of using a synthetic peptide-directed vaccinology approach to target epitopes of methanogen surface proteins was demonstrated. A prophage genome was described and its lytic enzyme, endoisopeptidase PeiR, was shown to lyse M1 cells in pure culture. A predicted stimulation of M1 growth by alcohols was demonstrated and microarray analyses indicated up-regulation of methanogenesis genes during co-culture with a hydrogen (H(2)) producing rumen bacterium. We also report the discovery of non-ribosomal peptide synthetases in M. ruminantium M1, the first reported in archaeal species.

CONCLUSIONS/SIGNIFICANCE

The M1 genome sequence provides new insights into the lifestyle and cellular processes of this important rumen methanogen. It also defines vaccine and chemogenomic targets for broad inhibition of rumen methanogens and represents a significant contribution to worldwide efforts to mitigate ruminant methane emissions and reduce production of anthropogenic greenhouse gases.

Monitoring bacterial community of human gut microbiota reveals an increase in Lactobacillus in obese patients and Methanogens in anorexic patients

Background

Studies of the bacterial communities of the gut microbiota have revealed a shift in the ratio of Firmicutes and Bacteroidetes in obese patients. Determining the variations of microbial communities in feces may be beneficial for the identification of specific profiles in patients with abnormal weights. The roles of the archaeon Methanobrevibacter smithii and Lactobacillus species have not been described in these studies.

Methods and Findings

We developed an efficient and robust real-time PCR tool that includes a plasmid-based internal control and allows for quantification of the bacterial divisions Bacteroidetes, Firmicutes, and Lactobacillus as well as the methanogen M. smithii. We applied this technique to the feces of 20 obese subjects, 9 patients with anorexia nervosa, and 20 normal-weight healthy controls. Our results confirmed a reduction in the Bacteroidetes community in obese patients (p<0.01). We found a significantly higher Lactobacillus species concentration in obese patients than in lean controls (p = 0.0197) or anorexic patients (p = 0.0332). The M. smithii concentration was much higher in anorexic patients than in the lean population (p = 0.0171).

Conclusions

Lactobacillus species are widely used as growth promoters in the farm industry and are now linked to obesity in humans. The study of the bacterial flora in anorexic patients revealed an increase in M. smithii. This increase might represent an adaptive use of nutrients in this population.

Thermophilic degradation of phenolic compounds in lab scale hybrid up flow anaerobic sludge blanket reactors

This Study describes the feasibility of anaerobic degradation of United States Environmental Protection Agency (USEPA) listed 4-chloro-2-nitrophenol (4C-2-NP), 2-chloro-4-nitrophenol (2C-4-NP), 2-chloro-5-methylphenol (2C-5-MP) from a simulated wastewater using four identical 7L bench scale hybrid up flow anaerobic sludge blankets (HUASBs) at five different hydraulic retention times (HRTs) under thermophilic condition (55+/-3 degrees C). The substrate to co-substrate ratios were maintained between 1:33.3 and 1:166.6. Continuous monitoring of parameters like pH, volatile fatty acids (VFAs) accumulation, oxidation reduction potential, chemical oxygen demand (COD), alkalinity, gas productions, methane percentages were carried out along with compound reduction to asses the efficiency of biodegradation. The compound reduction was estimated by using spectrophotometric methods and further validated with high-performance liquid chromatography (HPLC). Optimum HRT values were observed at 24h. Optimum ratio of substrate (phenolic compounds) to co-substrate (glucose) was 1:100. Scanning electron micrographs show that the granules were composed of thermophilic Methanobrevibacter and thermophilic Methanothrix like bacteria.

Genomic and metabolic adaptations of Methanobrevibacter smithii to the human gut

The human gut is home to trillions of microbes, thousands of bacterial phylotypes, as well as hydrogen-consuming methanogenic archaea. Studies in gnotobiotic mice indicate that Methanobrevibacter smithii, the dominant archaeon in the human gut ecosystem, affects the specificity and efficiency of bacterial digestion of dietary polysaccharides, thereby influencing host calorie harvest and adiposity. Metagenomic studies of the gut microbial communities of genetically obese mice and their lean littermates have shown that the former contain an enhanced representation of genes involved in polysaccharide degradation, possess more archaea, and exhibit a greater capacity to promote adiposity when transplanted into germ-free recipients. These findings have led to the hypothesis that M. smithii may be a therapeutic target for reducing energy harvest in obese humans. To explore this possibility, we have sequenced its 1,853,160-bp genome and compared it to other human gut-associated M. smithii strains and other Archaea. We have also examined M. smithii's transcriptome and metabolome in gnotobiotic mice that do or do not harbor Bacteroides thetaiotaomicron, a prominent saccharolytic bacterial member of our gut microbiota. Our results indicate that M. smithii is well equipped to persist in the distal intestine through (i) production of surface glycans resembling those found in the gut mucosa, (ii) regulated expression of adhesin-like proteins, (iii) consumption of a variety of fermentation products produced by saccharolytic bacteria, and (iv) effective competition for nitrogenous nutrient pools. These findings provide a framework for designing strategies to change the representation and/or properties of M. smithii in the human gut microbiota.

Molecular diversity of methanogens in feedlot cattle from Ontario and Prince Edward Island, Canada

The molecular diversity of rumen methanogens in feedlot cattle and the composition of the methanogen populations in these animals from two geographic locations were investigated using 16S rRNA gene libraries prepared from pooled PCR products from 10 animals in Ontario (127 clones) and 10 animals from Prince Edward Island (114 clones). A total of 241 clones were examined, with Methanobrevibacter ruminantium accounting for more than one-third (85 clones) of the clones identified. From these 241 clones, 23 different 16S rRNA phylotypes were identified. Feedlot cattle from Ontario, which were fed a corn-based diet, revealed 11 phylotypes (38 clones) not found in feedlot cattle from Prince Edward Island, whereas the Prince Edward Island cattle, which were fed potato by-products as a finishing diet, had 7 phylotypes (42 clones) not found in cattle from Ontario. Five sequences, representing the remaining 161 clones (67% of the clones), were common in both herds. Of the 23 different sequences, 10 sequences (136 clones) were 89.8 to 100% similar to those from cultivated methanogens belonging to the orders Methanobacteriales, Methanomicrobiales, and Methanosarcinales, and the remaining 13 sequences (105 clones) were 74.1 to 75.8% similar to those from Thermoplasma volcanium and Thermoplasma acidophilum. Overall, nine possible new species were identified from the two clone libraries, including two new species belonging to the order Methanobacteriales and a new genus/species within the order Methanosarcinales. From the present survey, it is difficult to conclude whether the geographical isolation between these two herds or differences between the two finishing diets directly influenced community structure in the rumen. Further studies are warranted to properly assess the differences between these two finishing diets.

Methanobrevibacter millerae sp. nov. and Methanobrevibacter olleyae sp. nov., methanogens from the ovine and bovine rumen that can utilize formate for growth

Four formate-utilizing methanogens were isolated from ovine (strain KM1H5-1PT) and bovine (strains AK-87, OCP and ZA-10T) rumen contents. Based on 16S rRNA gene sequence analysis, the methanogen strains were found to belong to the order Methanobacteriales in the genus Methanobrevibacter. Strains ZA-10T and KM1H5-1PT gained energy for growth by the reduction of CO2 to CH4 using H2 or formate exclusively as electron donors. Increasing formate concentrations to 220 mM in batch cultures increased the growth of strain KM1H5-1PT but did not affect the growth of strain ZA-10T. Substrate specificity and resistance to cell-wall lysis supported the affiliation of the strains to the genus Methanobrevibacter. Strains ZA-10T and KM1H5-1PT showed 16S rRNA gene sequence similarity of 98.0 and 98.6 % to their closest recognized relatives, Methanobrevibacter thaueri CWT and Methanobrevibacter ruminantium M1T, respectively. DNA–DNA hybridization experiments indicated that the strains were not affiliated at the species level to their closest recognized relatives, with DNA reassociation values of only 28 % between strains ZA-10T and Methanobrevibacter thaueri CWT and <25 % between strains KM1H5-1PT and Methanobrevibacter ruminantium M1T. Based on the data presented, the new strains are considered to represent two novel species of the genus Methanobrevibacter, for which the names Methanobrevibacter millerae sp. nov. (type strain ZA-10T=DSM 16643T=OCM 820T) and Methanobrevibacter olleyae sp. nov. (type strain KM1H5-1PT=DSM 16632T=OCM 841T) are proposed.

Identification and quantification of methanogenic Archaea in adult chicken ceca

By using molecular methods for the identification and quantification of methanogenic archaea in adult chicken ceca, 16S rRNA genes of 11 different phylotypes, 10 of which were 99% similar to Methanobrevibacter woesei, were found. Methanogen populations, as assessed by cultivation, and the 16S rRNA copy number were between 6.38 and 8.23 cells/g (wet weight) and 5.50 and 7.19 log(10)/g (wet weight), respectively.

Purification and characterization of Fe-containing superoxide dismutase from Methanobrevibacter arboriphilus strain AZ

Superoxide dismutase (SOD) was purified from cells of the strict anaerobic methanogenic archaeon Methanobrevibacter arboriphilus strain AZ. The four-step purification procedure resulted in enzyme with specific activity of 3970 units/mg and yield of 22%. It was shown that the SOD is a Fe-containing homotetramer composed of subunits of 21.2 kD each. Sodium azide (13.5 mM), unlike KCN, inhibits the activity of the SOD. Hydrogen peroxide (0.5 mM) inactivates the enzyme, which is consistent with the properties of the known Fe-containing SODs from methanogenic Archaea.

H2 and acetate transfers during xylan fermentation between a butyrate-producing xylanolytic species and hydrogenotrophic microorganisms from the human gut

The aim of this work was to investigate in vitro interrelationships during xylan fermentation between an H2 and butyrate-producing xylanolytic species recently isolated in our laboratory from human faeces and identified as Roseburia intestinalis and the H2-utilizing acetogen Ruminococcus hydrogenotrophicus or the methanogen Methanobrevibacter smithii. H2 transfer between M. smithii or Ru. hydrogenotrophicus and the xylanolytic species was evidenced, confirming the great potential of these H2-consuming microorganisms to reutilize fermentative H2 during fibre fermentation in the gut. In addition, acetate transfer was demonstrated between the xylanolytic Roseburia sp. and the acetogenic species, both metabolites transfers leading to butyric fermentation of oat xylan without production of H2.

Reducing methane emissions in sheep by immunization against rumen methanogens

This work was conducted to determine if methane emissions from sheep immunized with an anti-methanogen vaccine were significantly lower than methane emissions from non-immunized sheep, to test the effectiveness of two different vaccine formulations (VF) on methane abatement, and to compare methane emissions measured using a closed-circuit respiration chamber and the sulphur-hexafluoride (SF6) tracer technique. Thirty mature wether sheep were randomly allocated to three treatment groups (n = 10). One group received an immunization of adjuvant only on days 0 and 153 (control), a second group received an immunization with a 3-methanogen mix on days 0 and 153 (VF3 + 3), and a third group received an immunization of a 7-methanogen mix on day 0 followed by a 3-methanogen mix on day 153 (VF7 + 3). Four weeks post-secondary immunization, there was a significant 7.7% reduction in methane production per kg dry matter intake in the VF7 + 3 group compared to the controls (P = 0.051). However, methane emissions from sheep immunized with VF7 + 3 were not significantly different when compared to the sheep in the control group (P = 0.883). The average IgG and IgA antibody titres in both plasma and saliva of the VF3 + 3 immunized sheep were four to nine times higher than those immunized with VF7 + 3 (P< 0.001) at both 3 and 6 weeks post-secondary immunization. Data also revealed that SF6 methane estimates were consistently higher than the respiration chamber estimates and that there was no significant correlation between the SF6 methane estimates and the respiration chamber methane estimates (R2 = 0.11).

Application of Methanobrevibacter acididurans in anaerobic digestion

To operate anaerobic digesters successfully under acidic conditions, hydrogen utilizing methanogens which can grow efficiently at low pH and tolerate high volatile fatty acids (VFA) are desirable. An acid tolerant hydrogenotrophic methanogen viz. Methanobrevibacter acididurans isolated from slurry of an anaerobic digester running on alcohol distillery wastewater has been described earlier by this lab. This organism could grow optimally at pH 6.0. In the experiments reported herein, M. acididurans showed better methanogenesis under acidic conditions with high VFA, particularly acetate, than Methanobacterium bryantii, a common hydrogenotrophic inhabitant of anaerobic digesters. Addition of M. acididurans culture to digesting slurry of acidogenic as well as methanogenic digesters running on distillery wastewater showed increase in methane production and decrease in accumulation of volatile fatty acids. The results proved the feasibility of application of M. acididurans in anaerobic digesters.