Irritable Bowel Syndrome
Nicole M. Farmer, Andres Victor Ardisson Korat in Cooking for Health and Disease Prevention, 2022
Another proposed mechanism for the effect of FODMAPs has to do with bacterial fermentation and SIBO (Sachdeva et al., 2011). The theory goes that these poorly absorbed carbohydrates are excellent sources of food for an overgrowth of bacteria in the small intestine. These bacteria and sometimes archaea (single-celled nonbacterial organisms) ferment the carbohydrates and release different gases such as hydrogen and methane (recent evidence points to hydrogen sulfide, as well) (Banik et al. 2016). The gases released can cause the symptoms of bloating and also lead to cramping, pain, and changes in the motility of the small intestine.
Inorganic Chemical Pollutants
William J. Rea, Kalpana D. Patel in Reversibility of Chronic Disease and Hypersensitivity, Volume 4, 2017
In the absence of genome sequences for all Hg-methylating organisms, the generality of the present findings cannot yet be ascertained. However, their interpretation is in agreement with all currently available sequence information for methylating bacteria and archaea. The presence of the hgcAB cluster in the genomes of several sequenced, but so far untested, microorganisms leads them to hypothesize that these organisms are also capable of methylating mercury. The gene cluster appears to be quite sporadically distributed across two phyla of bacteria (Proteobacteria and Firmicutes) and one phylum of archaea (Euryarchaeota). Organisms possessing the two-gene cluster include 24 strains of Deltaproteobacteria, 16 Clostridia, 1 Negativicutes, and 11 Methanomicrobia. Interestingly, they also found these genes in a psychrophile,583 in a thermophile,584 and in a human commensal methanogen.585 The sporadic distribution of these genes and the lack of an obvious selective advantage related to mercury toxicity raise important questions regarding their physiological roles. Identification of these genes is a critical step linking specific microorganisms and environmental factors that influence microbial Hg methylation in aquatic ecosystems.
Archaeosomes for Skin Injuries
Andreia Ascenso, Sandra Simões, Helena Ribeiro in Carrier-Mediated Dermal Delivery, 2017
In view to optimize the performance of archaeosomes, specific archaeal lipid membrane properties have to be considered: (i) the ether linkages are more stable than esters over a wide range of pH, high temperature and the branching methyl groups help to reduce crystallization (membrane lipids in the liquid crystalline state at ambient temperature) and membrane permeability (steric hindrance of the methyl side groups); (ii) the saturated alkyl chains would impart stability towards oxidative degradation; (iii) the unusual stereochemistry of the glycerol backbone (opposite to mesophilic organisms) would ensure resistance to attack by phospholipases released by other organisms; (iv) the bipolar lipids span the membranes and enhance their stability properties; and (v) the addition of cyclic structures (in particular five-membered rings) in the transmembrane portion of the lipids appears to be a thermoadaptive response, resulting in enhanced membrane packing and reduced membrane fluidity [24].
Gut non-bacterial microbiota contributing to alcohol-associated liver disease
Published in Gut Microbes, 2021
Wenkang Gao, Yixin Zhu, Jin Ye, Huikuan Chu
Archaea were originally discovered and isolated from ecosystems with extreme conditions, including environments with high temperature, strong acid or base, and high ion concentration. However, with the continuous advancing of detection techniques, archaea had also been found in some mild environments such as the ocean ecosystems.145–149 Archaea are similar to bacteria in terms of shape, size, and genetic information expression including DNA replication, RNA transcription, and protein synthesis. Beside these similarities, there are also some obvious differences between archaea and bacteria. For instance, the archaeal cell walls do not contain peptidoglycans,150 and their cell membranes are composed of L-glycerol-ether/isoprenoid lipids, which are more stable and rigid than bacterial.151 Moreover, due to its special metabolic patterns, archaea can use sunlight, inorganic or organic substances as energy sources.152
Profiling the microbial contamination in aviation fuel from an airport
Published in Biofouling, 2019
Dong Hu, Wenfang Lin, Jie Zeng, Peng Wu, Menglu Zhang, Lizheng Guo, Chengsong Ye, Kun Wan, Xin Yu
Ascomycota and Euryarchaeota were the dominant fungal and archaeal phyla, respectively. The most prominent fungal contaminants in these selected fuel samples was Amorphotheca, and members of the genus Alternaria were also confirmed to be an active fungal contaminant (Darby et al. 2001). Surprisingly, archaea, which were neglected in previous studies (Hill T 2003; Rauch et al. 2006), were detected with a relatively high abundance (9%) in this study (Figure 2(A)). It has been shown that Methanosaeta species (Figure 2(C)), belonging to Euryarchaeota, can accept electrons directly from metallic coupons for the production of methane (Rotaru et al. 2014), indicating that Methanosaeta may play a role in MIC. In addition, sequences related to archaea have been found in petroleum reservoirs (Li et al. 2017), oil wells (Duncan et al. 2009), diesel storage tanks (de Azambuja et al. 2017), and automotive fuel tanks (Williamson 2007).
The rumen microbiome: a crucial consideration when optimising milk and meat production and nitrogen utilisation efficiency
Published in Gut Microbes, 2019
Chloe Matthews, Fiona Crispie, Eva Lewis, Michael Reid, Paul W. O’Toole, Paul D. Cotter
Archaea, in general, have a broad spectrum of unusual and distinctive metabolisms, enabling them to survive in a variety of different environments. Rumen archaea are strictly anaerobic and are the only known microorganisms present in the rumen capable of producing methane.32 Such archaea are referred to as methanogens. Archaea are found in the rumen in the range of 106 to 108 cells per ml, accounting for less than 4% of the microbial community.33 Archaea are found at the bottom of the trophic chain due to their need to use the end products of fermentation as substrates.8 The domain Archaea is broken into two different kingdoms; Euryarchaeota, consisting of methanogens and extreme halophiles, and Crenarchaeota, consisting of hyperthermophiles and nonthermophiles.34 Methanogens found in the kingdom Euryarchaeota require a very low redox potential and are among the strictest anaerobes known.35 According to meta-analysis of global data, 90% of rumen methanogens belong to the following genera36,37; Methanobrevibacter (63.2% of methanogen population), Methanomicrobium (7.7% of methanogen population) Methanosphaera (9.8%) “Rumen Cluster C”, now referred to as Thermoplasma (7.4%) and Methanobacterium (1.2%). Most methanogens remove hydrogen gas by reducing CO2 with hydrogen gas to form methane. In contrast, Methanosphaera stadtmanae only produces methane through the reduction of methanol with H2, having one of the strictest energy metabolisms of all methanogenic archaea. Producing methane keeps hydrogen concentrations in the rumen low, allowing methanogens to promote the growth of other species, and enabling a more efficient fermentation.11 However, methane produced in the rumen is eructated, leading to atmospheric pollution. Efforts to mitigate rumen methane emissions include vaccines (targeting rumen methanogens through the generation of antibodies to selected methanogen antigens that enter via saliva, binding to targets on the methanogens),38 small-molecule inhibitors (targets enzymes essential for the growth of methanogens), additives and breeding approaches. In a study carried out by Goopy et al.,39 it was found that sheep that emitted low methane levels had a smaller rumen in comparison to high methane-emitting sheep. There was no difference in dry matter intake or digestibility between the two groups. The study also found that low methane-emitting animals had a shorter mean retention time for both solid and liquid phase. This may be the basis for breeding animals with a smaller rumen size to reduce methane emissions. However, dietary manipulation is regarded the most effective and straightforward method of lowering rumen methane emissions,40 as selective breeding is slow and selection of specific traits may affect favourable variants.
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