Metagenomics Reveals Dominant Unusual Sulfur Oxidizers Inhabiting Active Hydrothermal Chimneys From the Southwest Indian Ridge

Abstract

The deep-sea hydrothermal vents (DSHVs) in the Southwest Indian Ridge (SWIR) are formed by specific geological settings. However, the community structure and ecological function of the microbial inhabitants on the sulfide chimneys of active hydrothermal vents remain largely unknown. In this study, our analyses of 16S rRNA gene amplicons and 16S rRNA metagenomic reads showed the dominance of sulfur-oxidizing Ectothiorhodospiraceae, Thiomicrorhabdus, Sulfurimonas, and Sulfurovum on the wall of two active hydrothermal chimneys. Compared with the inactive hydrothermal sediments of SWIR, the active hydrothermal chimneys lacked sulfur-reducing bacteria. The metabolic potentials of the retrieved 82 metagenome-assembled genomes (MAGs) suggest that sulfur oxidation might be conducted by Thiohalomonadales (classified as Ectothiorhodospiraceae based on 16S rRNA gene amplicons), Sulfurovaceae, Hyphomicrobiaceae, Thiotrichaceae, Thiomicrospiraceae, and Rhodobacteraceae. For CO2 fixation, the Calvin-Benson-Bassham and reductive TCA pathways were employed by these bacteria. In Thiohalomonadales MAGs, we revealed putative phytochrome, carotenoid precursor, and squalene synthesis pathways, indicating a possible capacity of Thiohalomonadales in adaptation to dynamics redox conditions and the utilization of red light from the hot hydrothermal chimneys for photolithotrophic growth. This study, therefore, reveals unique microbiomes and their genomic features in the active hydrothermal chimneys of SWIR, which casts light on ecosystem establishment and development in hydrothermal fields and the deep biosphere.

Unique deep-sea bacterial assemblages thriving on different natural organic matters delivered via in situ incubators

“…S6). Both Arcobacteraceae and Sulfurovaceae are typical chemoautotrophic marine SOBs [37][38][39]. In our enrichments, Arcobacteraceae was more abundant, prevalent, and diverse than Sulfurovaceae (Fig.…”

“…S4). Most of these bacterial members were anaerobes or facultative anaerobes, like Marini laceae [33], Spirochaetaceae [34], Psychromonadaceae [35], Fusobacteriaceae [36], sulphur-oxidizing bacteria (SOBs) of Arcobacteraceae and Sulfurovaceae [37][38][39], sulphur-reducing bacteria of Sulfurospirillaceae [40], and sulphate-reducing bacteria (SRBs) of Desulfobulbaceae and Desulfobacteraceae [41,42]. In the in situ seawater collected by CICs, the putative anaerobic bacteria Woeseiaceae/JTB255 and SAR202 were recovered, which have been recognized as cosmopolitan and abundant core members of deep-sea surface sediments [43] and benthic water [44][45][46], respectively.…”

“…S8). Arcobacteraceae have been identi ed as emerging pathogens potentially cause health risks to humans and animals [54] and also occur in hydrothermal vents like Sulfurovaceae [37,55]. However, phylogenetic analysis showed that the dominant species of Arcobacteraceae (represented by OTU9977, OTU4225, OTU6340, and OTU1752) were obviously separated from those associated with humans and animals or with hydrothermal origins, but clustered onto a branch with those from the deep-sea wood-falls (Fig.…”

Variation in epibiotic bacteria on two squat lobster species of Munidopsidae

“…Our results showed that chemosynthetic bacteria, including Thiotrichales , Methylococcales , and Campylobacterales , dominated the MV carapace epibiotic bacterial community. Campylobacterales species often play a crucial role in the sulfur, nitrogen, and hydrogen cycles, as oxidizers or reducers ( Wang Y. et al, 2022 ). Methylococcales belongs to facultative anaerobic bacteria and exhibits prominent capacity for the anaerobic oxidation of methane ( Bhattarai et al, 2019 ).…”