a novel Verrucomicrobiota species isolated from Reticulitermes chinensis gives insights of high adaptability of symbiotic bacteria to termite gut ecosystem

Verrucomicrobiota is widely distributed in various habitats including insect guts. It was found to be prevalent in almost all investigated termite guts, whereas their physiological functions are not very clear. In this study we characterized the physiological and genomic properties of Verrucomicrobiota strain TSB47T isolated from Reticulitermes chinensis. The cells of strain TSB47T were Gram-stain-negative, non-motile, and non-spore-forming coccoid with one or more warts. 16S rRNA gene analysis showed that the closest relatives of strain TSB47T were Opitutaceae strain TAV1 and Ereboglobus luteus Ho45T (98.3% and 95.4% sequence similarity, respectively). Whole genome analysis revealed that there are a large number of glycoside hydrolase genes, amino acid metabolism genes, complete Mo-Fe nitrogenase and Fe-Fe nitrogenase gene clusters, as well as cbb3-type cytochrome oxidase gene in the genome of strain TSB47T. Strain TSB47T grows well under anaerobic and microaerophilic conditions with a strong tolerance to oxygen. Physiological and genomic characters of strain TSB47T indicated its high adaptability to termite gut ecosystem. Based on phenotypic and phylogenetic evidence, we suggest strain TSB47T as the type species of a novel genus in the family Opitutaceae, for which the name Termitidicoccus mucosus sp. nov. is proposed. The type strain is TSB47T (CCTCC AB2022447T; KCTC 102044T).

Complete genome sequence of Opitutales bacterium strain ASA1, isolated from soil

We present the complete genome of Opitutales bacterium ASA1, isolated from soil. The genome is 5,821,695 bp with 4,638 protein-coding sequences. The genome data suggest that this strain belongs to the class Opitutae of the phylum Verrucomicrobiota, and its genome has six unique biosynthetic gene clusters associated with secondary metabolites.

Description of the first cultured representative of "Candidatus Synoicihabitans" genus, isolated from deep-sea sediment of South China Sea

In this study we describe the first cultured representative of Candidatus Synoicihabitans genus, a novel strain designated as LMO-M01T, isolated from deep-sea sediment of South China Sea. This bacterium is a facultative aerobe, Gram-negative, non-motile, and has a globular-shaped morphology, with light greenish, small, and circular colonies. Analysis of the 16S rRNA gene sequences of strain LMO-M01T showed less than 93% similarity to its closest cultured members. Furthermore, employing advanced phylogenomic methods such as comparative genome analysis, average nucleotide identity (ANI), average amino acids identity (AAI), and digital DNA-DNA hybridization (dDDH), placed this novel species within the candidatus genus Synoicihabitans of the family Opitutaceae, Phylum Verrucomicrobiota. The genomic analysis of strain LMO-M01T revealed 175 genes, encoding putative carbohydrate-active enzymes. This suggests its metabolic potential to degrade and utilize complex polysaccharides, indicating a significant role in carbon cycling and nutrient turnover in deep-sea sediment. In addition, the strain's physiological capacity to utilize diverse biopolymers such as lignin, xylan, starch, and agar as sole carbon source opens up possibilities for sustainable energy production and environmental remediation. Moreover, the genome sequence of this newly isolated strain has been identified across diverse ecosystems, including marine sediment, fresh water, coral, soil, plants, and activated sludge highlighting its ecological significance and adaptability to various environments. The recovery of strain LMO-M01T holds promise for taxonomical, ecological and biotechnological applications. Based on the polyphasic data, we propose that this ecologically important strain LMO-M01T represents a novel genus (previously Candidatus) within the family Opitutaceae of phylum Verrucomicrobiota, for which the name Synoicihabitans lomoniglobus gen. nov., sp. nov. was proposed. The type of strain is LMO-M01T (= CGMCC 1.61593T = KCTC 92913T).

Impact of elobixibat on liver tumors, microbiome, and bile acid levels in a mouse model of nonalcoholic steatohepatitis

BACKGROUND

Elevated bile acid levels have been associated with liver tumors in fatty liver. Ileal bile acid transporter inhibitors may inhibit bile acid absorption in the distal ileum and increase bile acid levels in the colon, potentially decreasing the serum and hepatic bile acid levels. This study aimed to investigate the impact of these factors on liver tumor.

METHODS

C57BL/6J mice received a one-time intraperitoneal injection of 25-mg/kg diethylnitrosamine. They were fed a choline-deficient high-fat diet for 20 weeks starting from 8 weeks of age, with or without elobixibat (EA Pharma, Tokyo, Japan).

RESULTS

Both groups showed liver fat accumulation and fibrosis, with no significant differences between the two groups. However, mice with elobixibat showed fewer liver tumors. The total serum bile acid levels, including free, tauro-conjugated, glyco-conjugated, and tauro-α/β-muricholic acids in the liver, were noticeably reduced following elobixibat treatment. The proportion of gram-positive bacteria in feces was significantly lower in the group treated with elobixibat (5.4%) than in the group without elobixibat (33.7%).

CONCLUSION

Elobixibat suppressed tumor growth by inhibiting bile acid reabsorption, and decreasing total bile acid and primary bile acid levels in the serum and liver. Additionally, the presence of bile acids in the colon may have led to a significant reduction in the proportion of gram-positive bacteria, potentially resulting in decreased secondary bile acid synthesis.

Identification and characterization of an abundant lipoprotein from Methylacidiphilum fumariolicum SolV

Bacterial lipoproteins are characterized by the presence of a conserved N-terminal lipid-modified cysteine residue that allows the hydrophilic protein to anchor into bacterial cell membranes. These lipoproteins play essential roles in a wide variety of physiological processes. Based on transcriptome analysis of the verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV, we identified a highly expressed lipoprotein, WP_009060351 (139 amino acids), in its genome. The first 86 amino acids are specific for the methanotrophic genera Methylacidiphilum and Methylacidmicrobium, while the last 53 amino acids are present only in lipoproteins of members from the phylum Verrucomicrobiota (Hedlund). Heterologous expression of WP_009060351 in Escherichia coli revealed a 25-kDa dimeric protein and a 60-kDa tetrameric protein. Immunoblotting showed that WP_009060351 was present in the total membrane protein and peptidoglycan fractions of M. fumariolicum SolV. The results suggest an involvement of lipoprotein WP_009060351 in the linkage between the outer membrane and the peptidoglycan.