Background Our understanding of the gut microbiota of animals is largely based on studies of mammals. To better understand the evolutionary basis of symbiotic relationships between animal hosts and indigenous microbes, it is necessary to investigate the gut microbiota of non-mammalian vertebrate species. In particular, fish have the highest species diversity among groups of vertebrates, with approximately 33,000 species. In this study, we comprehensively characterized gut bacterial communities in fish. Results We analyzed 227 individual fish representing 14 orders, 42 families, 79 genera, and 85 species. The fish gut microbiota was dominated by Proteobacteria (51.7%) and Firmicutes (13.5%), different from the dominant taxa reported in terrestrial vertebrates (Firmicutes and Bacteroidetes). The gut microbial community in fish was more strongly shaped by host habitat than by host taxonomy or trophic level. Using a machine learning approach trained on the microbial community composition or predicted functional profiles, we found that the host habitat exhibited the highest classification accuracy. Principal coordinate analysis revealed that the gut bacterial community of fish differs significantly from those of other vertebrate classes (reptiles, birds, and mammals). Conclusions Collectively, these data provide a reference for future studies of the gut microbiome of aquatic animals as well as insights into the relationship between fish and their gut bacteria, including the key role of host habitat and the distinct compositions in comparison with those of mammals, reptiles, and birds.

Gintonin is a novel ginseng-derived lysophosphatidic acid (LPA) receptor ligand. Oral administration of gintonin ameliorates learning and memory dysfunctions in Alzheimer’s disease (AD) animal models. The brain cholinergic system plays a key role in cognitive functions. The brains of AD patients show a reduction in acetylcholine concentration caused by cholinergic system impairments. However, little is known about the role of LPA in the cholinergic system. In this study, we used gintonin to investigate the effect of LPA receptor activation on the cholinergic system in vitro and in vivo using wild-type and AD animal models. Gintonin induced [Ca2+]i transient in cultured mouse hippocampal neural progenitor cells (NPCs). Gintonin-mediated [Ca2+]i transients were linked to stimulation of acetylcholine release through LPA receptor activation. Oral administration of gintonin-enriched fraction (25, 50, or 100 mg/kg, 3 weeks) significantly attenuated scopolamine-induced memory impairment. Oral administration of gintonin (25 or 50 mg/kg, 2 weeks) also significantly attenuated amyloid-β protein (Aβ)-induced cholinergic dysfunctions, such as decreased acetylcholine concentration, decreased choline acetyltransferase (ChAT) activity and immunoreactivity, and increased acetylcholine esterase (AChE) activity. In a transgenic AD mouse model, long-term oral administration of gintonin (25 or 50 mg/kg, 3 months) also attenuated AD-related cholinergic impairments. In this study, we showed that activation of G protein-coupled LPA receptors by gintonin is coupled to the regulation of cholinergic functions. Furthermore, this study showed that gintonin could be a novel agent for the restoration of cholinergic system damages due to Aβ and could be utilized for AD prevention or therapy.

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Background: Archaea are one of the least-studied members of the gut-dwelling autochthonous microbiota. Few studies have reported the dominance of methanogens in the archaeal microbiome (archaeome) of the human gut, although limited information regarding the diversity and abundance of other archaeal phylotypes is available. Results: We surveyed the archaeome of faecal samples collected from 897 East Asian subjects living in South Korea. In total, 42.47% faecal samples were positive for archaeal colonisation; these were subsequently subjected to archaeal 16S rRNA gene deep sequencing and real-time quantitative polymerase chain reaction-based abundance estimation. The mean archaeal relative abundance was 10.24 ± 4.58% of the total bacterial and archaeal abundance. We observed extensive colonisation of haloarchaea (95.54%) in the archaea-positive faecal samples, with 9.63% mean relative abundance in archaeal communities. Haloarchaea were relatively more abundant than methanogens in some samples. The presence of haloarchaea was also verified by fluorescence in situ hybridisation analysis. Owing to large inter-individual variations, we categorised the human gut archaeome into four archaeal enterotypes. Conclusions: The study demonstrated that the human gut archaeome is indigenous, responsive, and functional, expanding our understanding of the archaeal signature in the gut of human individuals.

Orbus sasakiae sp. nov., a bacterium isolated from the gut of the butterfly Sasakia charonda, and emended description of the genus Orbus Joon Yong Kim, Jina Lee, Na-Ri Shin, Ji-Hyun Yun, Tae Woong Whon, Min-Soo Kim, Mi-Ja Jung, Seong Woon Roh, Dong-Wook Hyun and Jin-Woo Bae ). An emended description of the genus Orbus is provided.Orbus, a genus in the class Gammaproteobacteria, was first introduced by Volkmann et al. (2010). At the time of writing, Orbus hercynius is the only recognized species within this genus and was originally isolated from the faeces of wild boars in Germany. The major fatty acids of the genus Orbus are monounsaturated, even-numbered, straight-chain C 18 (C 18 : 1 v7c) and saturated, even-numbered, straight-chain C 16 (C 16 : 0 ) components (Volkmann et al., 2010). Here, we isolated an Orbus-like strain, designated C7 T , from butterfly gut. Based on taxonomic characterization and phylogenetic analysis, we propose that strain C7T represents a novel species belonging to the genus Orbus. Strain C7T was isolated from the gut of the butterfly Sasakia charonda in South Korea. Cells were isolated by the standard dilution-plating method and were incubated under aerobic conditions at 20 u C on trypticase soy agar (TSA; Difco). To obtain pure cultures, a single colony was repeatedly transferred. Gram reactions were performed using a Gram staining kit (bioMérieux) according to the manufacturer's instructions. Cell morphology and Gram staining of strain C7T were observed using a light microscope (ECLIPSE 50i; Nikon). Motility was examined by the method of Tittsler & Sandholzer (1936). Growth under anaerobic conditions was monitored after 7 days incubation in an anaerobic chamber (N 2 /H 2 /CO 2 , 90 : 5 : 5) at 37 u C on TSA medium. The growth of strain C7 T on CIN agar medium (CIN; BBL) was tested. Based on the experiments described above, strain C7T was determined to be coccoid (0.5-1.0 mm in diameter), Gram-stain-negative, facultatively anaerobic and non-motile. Growth of strain C7T was observed on CIN agar. All experiments were performed in triplicate.Growth at different temperatures (4, 15, 20, 25, 30, 37, 45 and 65 u C), pH values (pH 4.0-11.0, at intervals of 1.0 pH unit) and NaCl concentrations (0, 1, 2, 3, 4, 5, 8, 10, 12 and 15 %, w/v) was tested in trypticase soy broth (TSB; Difco). pH was adjusted by adding the following buffers: 10 mM MES (C 6 H 13 NO 4 S) (for pH 4, 5 and 6), 10 mM TAPS (C 7 H 14 NO 6 S) (for pH 7, 8 and 9) or 10 mM Na 2 HPO 4 (for pH 10 and 11). The strains were cultivated in TSB at 20 u C for all experiments, unless stated otherwise. After incubation for 24 h, 48 h or 7 days, the turbidity of the cultures was measured as the optical density at 600 nm (OD 600 ) using a spectrophotometer (SYNERGY MX; BioTek). Strain C7T grew with 0-5 % (w/v) NaCl, atAbbreviations: PE, phosphatidylethanolamine; PG, phosphatidylglycerol.