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

Abstract

Background The transport of organic matters to the deep sea constantly occurs in global oceans and in accompany with simultaneous microbial remineralization. However, little is known about the impact of fast sinking organic complex on oceanic deep ecosystem and its interactions with microbes throughout the process of sinking and settling on the sea bottom. In this report, to observe the response of indigenous microorganisms to the newly input of organic matters, we developed a series of deep-sea in-situ incubators loaded on the seabed and seamount with various organic substrates of plant and animal origins. Results The bacterial diversity at the OTU level varied in accordance to organic substrates and geographic locations, but the functional groups are generally similar. The bacteria of Marinifilaceae were revealed as the key member; in addition, other key decomposers including Spirochaetaceae, Psychromonadaceae, Vibrionaceae, Moritellaceae, and Fusobacteriaceae were also recruited in most assemblages with varied abundance accordingly. Interestingly, nitrogen fixation inside the assemblages occurred in the process of polysaccharide decomposing. The microbial co-occurrence analysis revealed that nutrient availability and energy transfer determine relationships cooperation or competition. Within the assemblages stimulated by substrates short of nitrogen sources, the microbial network was dominated by cooperative relationships, whereas competition relationships overwhelmed the communities thriving on proteinous substrates. Conclusions These in-situ observations revealed a unique bacterial assemblage in decomposing diverse newly input organic matters, which may constitute the microbial pumps involved in carbon, sulphur, and nitrogen cycles in oceanic interior.

The frequent occurrence and metabolic versatility of Marinifilaceae bacteria involved in organic matter mineralization as a key member in global deep sea

“…S9-S10 , and Table S14 ), all of which are typically involved in strictly anaerobic fermentation for hydrogen production (61). These fermentation products can serve as carbon sources for sulphate-reducing bacteria, e.g., Desulfobulbaceae and Desulfobacteraceae, also dominating the animal tissue- and plant-detritus enrichments (33).…”

“…The five incubations respectively emended with wood chip, wheat bran, fish scale, fish tissue, and fish oil (DHA and EPA) were incubated at a flat-topped seamount in the Pacific Ocean (20.4059567° N, 160.7700883° E; 1622 m water depths) for 348 days. The detailed enrichment process and organic substrates refer to this previous article (33).…”

“…These fermentation products can serve as carbon sources for sulphate-reducing bacteria, e.g., Desulfobulbaceae and Desulfobacteraceae, also dominating the animal tissue-and plant-detritus enrichments (33).…”

“…We hypothesized that the microorganisms thriving on those remains sunk into the deep-sea may be different from the bacteria observed in the deep water column sampled with CTD cassettes, filter fractionation techniques, and sediment traps, because large pieces rich in OM do not constantly sink through the water column and settle to the seabed at every location. To identify the bacterial assemblage involved in the in situ transformation and degradation of the fast and sinking POM in the deep sea, we performed deep-sea in situ incubation amended with various natural animal and plant tissues in different oceans (preprint: https://doi.org/10.21203/rs.3.rs-1700182/v1) (33). After 4-12 months of incubation via an in situ incubation device landing on the seafloor, we found that bacteria of the family Marinifilaceae (MF) were the predominant members of both animal and plant tissue enrichments.…”