Zurabishvili, T. | Search bioRxiv

bioRxiv2024

Proteomic and Metabolomic Profiling of Archaeal Extracellular Vesicles from the Human Gut

One potential mechanism for microbiome-host, and microbiome constituents interaction and communication involves extracellular vesicles (EVs). Here, for the first time, we report the capability of two M. smithii strains (ALI and GRAZ-2), Candidatus M. intestini, and Methanosphaera stadtmanae, as underrepresented components of the gut microbiome, to produce EVs. Interesting, size, morphology, and composition of AEVs were comparable to bacterial EVs, as indicated by ultrastructure, composition, proteomic and metabolomic analyses; however, EVs were substantially less prevalent in the studied Archaea. When looking at the proteomics more precisely, although AEVs from M. smithii ALI and M. intestini were found to be carrying unique proteins (n=135 and n=30, respectively), the shared proteins in AEVs within this genus (n=229), were mostly adhesins(/like) proteins, or proteins with IG-like domains. One remarkable observation was the uptake of AEVs obtained from Methanosphaera stadtmanae and the studied Methanobrevibacter species by human monocytes and the subsequent IL-8 secretion.

microbiology↗

bioRxiv2024

Expanding the cultivable human archaeome: Methanobrevibacter intestini sp. nov. and strain Methanobrevibacter smithii GRAZ-2 from human feces

Two mesophilic, hydrogenotrophic methanogens, WWM1085 and M. smithii GRAZ-2 were isolated from human fecal samples. WWM1085 was isolated from an individual in the USA, and represents a novel species with in the genus Methanobrevibacter. M. smithii GRAZ-2 (= DSM 116045) was retrieved from fecal samples of a European, healthy female and represents a novel strain within this genus. Both Methanobrevibacter representatives form non-flagellated, short rods with variable morphologies and the capacity to form filaments. Both isolates showed the typical fluorescence of F420 and methane production. Compared to M. smithii GRAZ-2, WWM1085 did not accumulate formate when grown on H2 and CO2. The optimal growth conditions were at 37{degrees}C, and pH 7. Full genome sequencing revealed a genomic difference of WWM1085 to the type strain of M. smithii PS (type strain; DSM 861), with 93.55% ANI and major differences in the sequence of its mcrA gene (3.3% difference in nucleotide sequence). Differences in the 16S rRNA gene were very minor and thus distinction based on this sequence might not be possible. M. smithii GRAZ-2 was identified as a novel strain within the Methanobrevibacter genus (ANI 99.04 % to M. smithii PS). Due to the major differences of WWM1085 and M. smithii type strain PS in phenotypic, genomic and metabolic features, we propose M. intestini sp. nov. as a novel species with WWM1085 as the type strain (DSM 116060T = CECT 30992).

microbiology↗