Abstract
Resolving metabolisms of deep-sea microorganisms is crucial for understanding ocean energy cycling. Here, a strictly anaerobic, Gram-negative strain NS-1 was isolated from the deep-sea cold seep in the South China Sea. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain NS-1 was most closely related to the type strain Halocella cellulosilytica DSM 7362T (with 92.52% similarity). A combination of phylogenetic, genomic, and physiological traits with strain NS-1, was proposed to be representative of a novel genus in the family Halanaerobiaceae, for which Iocasia fonsfrigidae NS-1 was named. It is noteworthy that I. fonsfrigidae NS-1 could metabolize multiple carbohydrates including xylan, alginate, starch, and lignin, and thereby produce diverse fermentation products such as hydrogen, lactate, butyrate, and ethanol. The expressions of the key genes responsible for carbohydrate degradation as well as the production of the above small molecular substrates when strain NS-1 cultured under different conditions, were further analyzed by transcriptomic methods. We thus predicted that part of the ecological role of Iocasia sp. is likely in the fermentation of products from the degradation of diverse carbohydrates to produce hydrogen as well as other small molecules, which are in turn utilized by other members of cold seep microbes.
Highlights
Microbes inhabiting the deep sea represent a large portion of the biosphere, and resolving their ecology is crucial for understanding global ocean processes (Baker et al, 2021)
Analysis of the 16S rRNA sequence (1,444 bp) of strain NS-1 showed that it was a member of the family Halanaerobiaceae and possessed 92.52% sequence similarity with Halocella cellulosilytica DSM 7362T, a cellulose degradation bacterium isolated from the hypersaline (Simankova et al, 1993)
By measuring the amount of whole cellular protein of strain NS-1 growing under different conditions, it was clear that the growth of this bacterium was significantly increased with the supplement of respectively L-arabinose, fructose, galactose, glucose, xylan, maltose, D-mannose, rhamnose, starch, and sucrose in PTY medium (Figure 2)
Summary
Microbes inhabiting the deep sea represent a large portion of the biosphere, and resolving their ecology is crucial for understanding global ocean processes (Baker et al, 2021). Despite the global importance of these microorganisms, the majority of deep-sea microbial diversity remains uncultured and poorly characterized (Baker et al, 2021). Microbial cells take advantage of these small organic molecules (such as sugars, amino acids, fatty acid, organic acids, and so on) through multistep fermentation processes with the production of a range of volatile fatty acids (VFAs), such as formate, acetate, propionate, and butyrate, together with H2 and CO2. These VFAs are electron donors that support the growth of diverse bacteria (Gittel et al, 2008; Zhang et al, 2019b; Choi et al, 2021)
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