Effect of the macroalgaeAsparagopsis taxiformison methane production and the rumen microbiome assemblage
Breanna Michelle RoqueCharles BrookeJoshua LadauTamsen PolleyLyndsey MarshNegeen NajafiPramod PandeyLatika SinghJoan King SalwenEmiley A. Eloe‐FadroshE. KebreabMatthias Hess
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ABSTRACT Background Recent studies using batch-fermentation suggest that the red macroalgae Asparagopsis taxiformis might reduce methane (CH 4 ) emission from beef cattle by up to ~99% when added to rhodes grass hay, a common feed in the Australian beef industry. These experiments have shown significant reductions in methane without compromising other fermentation parameters (i.e. volatile fatty acid production) with A. taxiformis organic matter (OM) inclusion rates of up to 5%. In the study presented here, A. taxiformis was evaluated for its ability to reduce methane production from dairy cattle fed a mixed ration widely utilized in California; the largest milk producer in the US. Results Fermentation in a semi-continuous in-vitro rumen system suggests that A. taxiformis can reduce methane production from enteric fermentation in dairy cattle by 95% when added at a 5% OM inclusion rate without any obvious negative impacts on volatile fatty acid production. High-throughput 16S ribosomal RNA (rRNA) gene amplicon sequencing showed that seaweed amendment effects rumen microbiome communities consistent with the Anna Karenina hypothesis, with increased beta-diversity, over time scales of approximately three days. The relative abundance of methanogens in the fermentation vessels amended with A. taxiformis decreased significantly compared to control vessels, but this reduction in methanogen abundance was only significant when averaged over the course of the experiment. Alternatively, significant reductions of methane in the A. taxiformis amended vessels was measured in the early stages of the experiment. This suggests that A. taxiformis has an immediate effect on the metabolic functionality of rumen methanogens whereas its impact on microbiome assemblage, specifically methanogen abundance, is delayed. Conclusions The methane reducing effect of A. taxiformis during rumen fermentation makes this macroalgae a promising candidate as a biotic methane mitigation strategy in the largest milk producing state in the US. But its effect in-vivo (i.e. in dairy cattle) remains to be investigated in animal trials. Furthermore, to obtain a holistic understanding of the biochemistry responsible for the significant reduction of methane, gene expression profiles of the rumen microbiome and the host animal are warranted.Keywords:
Methanogen
Abstract This study investigated a possible role for primary bile acid in the control of methanogenesis in the human colon. Production of hydrogen and methane was measured in anaerobic faecal cultures derived from faeces of six ‘non‐methanogenic’ and three methanogenic healthy humans. Using a sensitive technique for gas measurement, methane was detected in all faecal cultures, including those from ‘non‐methanogenic’ humans. Bile acid inhibited methanogenesis in a dose‐response fashion in the in vitro ‘non‐methanogenic’ and methanogenic faecal cultures. Inhibition was significant at bile acid concentrations > 0.05%. Methanogenesis correlated with methanogen (methanogenic bacteria) numbers. If this inhibition occurs in vivo , then it would explain much of the epidemiology of non‐methanogenesis in humans. From an analysis of net hydrogen production by the faecal cultures, it is inferred that bile acid inhibits other hydrogen‐consuming bacteria in addition to methanogens. These in vitro data suggest a major role for bile acid in the accumulation of hydrogen gas in the colon. Possible links between bile acid induced accumulation of gas and irritable bowel syndrome are discussed.
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Coal-bed methane is one of the largest unconventional natural gas resources. Although microbial activity may greatly contribute to coal-bed methane formation, it is unclear whether the complex aromatic organic compounds present in coal can be used for methanogenesis. We show that deep subsurface-derived Methermicoccus methanogens can produce methane from more than 30 types of methoxylated aromatic compounds (MACs) as well as from coals containing MACs. In contrast to known methanogenesis pathways involving one- and two-carbon compounds, this "methoxydotrophic" mode of methanogenesis couples O-demethylation, CO2 reduction, and possibly acetyl-coenzyme A metabolism. Because MACs derived from lignin may occur widely in subsurface sediments, methoxydotrophic methanogenesis would play an important role in the formation of natural gas not limited to coal-bed methane and in the global carbon cycle.
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Abstract The objective of our study was to identify environmental conditions that structure lake sediment microbial communities and determine whether community composition explained inter‐lake variation in potential methanogenesis rates. We performed a comparative analysis of microbial communities and methanogenesis rates in 14 lake sediments along gradients of pH and primary productivity. Variation in methanogen community composition and non‐methanogen microbial community composition was best explained by pH and sediment organic matter content. However, these regulators of methanogen community structure were not associated with differences in methanogenesis rates. Instead, variation in lake methanogenesis rates was best explained by proxies for organic matter supplied to sediments (lake chlorophyll a concentration and sediment pore‐water total phosphorus) and the composition of the non‐methanogen microbial community. Our results suggest a role for sediment bacterial community in influencing methanogenesis via the supply of growth substrates.
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Summary Considering wide utilization and high methane fluxes from anaerobic biological stabilization ponds ( ABSP s), understanding the methanogenesis in ABSP s is of fundamental importance. Here we investigated the variation and impact factors of methanogenesis in seven ABSP s that spanned from the north to the south of China. Results showed that methanogen abundance (7.7 × 10 9 –8.7 × 10 10 copies g −1 dry sediment) and methanogenic activities (2.2–21.2 μmol CH 4 g −1 dry sediment h −1 ) were considerable for all sediments. Statistical analysis demonstrated that compared with other factors (ammonium, pH , COD and TOC ), mean annual temperature ( MAT ) showed the lowest P value and thus was the most important influencing factor for the methanogenic process. Besides, with the increasing MAT , methanogenic activity was enhanced mainly due to the shift of the dominant methanogenic pathway from acetoclastic (49.8–70.7%) in low MAT areas to hydrogenotrophic (42.0–54.6%) in high MAT areas. This shift of methanogenic pathway was also paralleled with changes in composition of bacterial communities. These results suggested that future global warming may reshape the composition of methanogen communities and lead to an increasing methane emission from ABSP s. Therefore, further research is urgently needed to globally estimate methane emissions from ABSP s and re‐examine the role of ABSP s in wastewater treatment.
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A rumen fistulated wether was used for continuous infusion of a 2‐bromoethanesulfonic acid (BES) solution (2 g/d in 50 ml of water). The infusion was started after introduction of a pulse dose of BES (2 g) into the rumen. Immediately after introduction of the pulse dose, methane concentration in rumen gases was lowered from about 40 to less than 1%, with concomittant decreases and increases in the molar proportions of acetic and propionic acids respectively in the rumen volatile fatty acids. After 4 days of infusion however, and despite repeated pulse dosage of BES, methanogenesis adapted to BES and methane concentration in rumen gases reached 20%. Addition of BES to incubations of rumen contents with hay resulted in 'considerable inhibition of methanogenesis. Extra addition of methanol in such incubations increased both acetate and methane production, whereas addition of formate had no effect. In a second experiment using a second rumen fistulated whether, a 4 day control period was followed by 10 days of daily introduction of 11 of cattle cecal contents into the rumen. The cattle cecal contents were collected from slaughterhouse cattle, filtered and kept at — 20°C until use. Comparison of in vitro fermentation of thawed with fresh contents showed absence of methanogenesis but not of reductive acetogenesis after freezing and thawing. Evidence for the latter was sought by calculation of metabolic hydrogen recoveries from amounts of end products formed in incubations. In a similar way, evidence for induction of reductive acetogenesis was sought from incubations in vitro, carried out with rumen contents obtained before, during and after introduction of cecal contents into the rumen. No such evidence was obtained.
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Methane production in the environment has been recognized as an important factor for the global warming. It is also important as a process for self-purification in the polluted environment. In this study, the author isolated methanogenic bacteria which live in a lake sediment and investigated the methanogenic activity of the isolated bacteria. The author also studied the distribution of methanogenic activity in a lake sediment by using sediment samples which were obtained from each depth of the sediment, and temperature effects to the methanogenic activities. One coccus bacterial strain of methanogenic bacteria isolated from the lake sediment was a hydrogen utilizing methanogen. It was impossible to isolate acetate utilizing methanogen from the lake sediment because of the coexisting bacteria other than methanogens. There were many differences between hydrogen utilizing methanogenesis and acetate utilizing methanogenesis. Methanogenesis from hydrogen dominated in the lake sediment, especially in the deeper sediment. This methanogenic activity was also observed at low temperature. Methanogenesis from acetate was active at the upper sediment which contained much organic compounds, but not so high as methanogenesis from hydrogen.
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