Microbial population structure along the water columns and sediments in the Diamantina and Kermadec trenches.

ABSTRACT:

Background

Microbes are widespread from the marine surface to the hadal zones and play a significant role in global biogeochemical cycling. Physicochemical properties of hadal zone shift with depth, in turn influencing the distribution profiles, biogeochemical functions, and adaptative mechanisms of microbial communities in hadal trenches. However, the ecological functions and evolutions of microbial communities along the surface water down to the sediments in the Diamantina and Kermadec trenches have been rarely studied.

Results

Here, we provided a detailed metagenomic analysis of samples along the water columns (0-6553 m) and sediments (3060-9232 m) in the Diamantina and Kermadec trenches. The euphotic waters had a significantly higher ɑ-diversity than the deep-sea waters and sediments (p < 0.05, ANOSIM). Clear inter/intra-trench discrepancies of microbial communities along water layers appeared, with remarkable vertical connectivity exhibited in the Diamantina Trench (97.5%) than the Kermadec Trench (88.8%). Positive correlations among Proteobacteria, Bacteroidota, Actinobacteria, and Thaumarchaeota in seawaters and between Proteobacteria and Chloroflexi in sediments were revealed from the co-occurrence network. Niche-specific microbial groups showed distinct dominant metabolic pathways in carbon fixation, nitrogen, and sulfur cycles. Furthermore, we reconstructed 119 metagenome-assembled genomes (MAGs) of Rhodobacterales, and their notably low ratios of non-synonymous substitutions to synonymous substitutions (pN/pS, 0.23) and high carbon atoms per residue side chain (C-ARSC, 2.86) in deep-sea sediments suggested a pronounced selection critical for their survival.

Conclusions

We found a clear connectivity of microbial communities in vertical profile, and discrepancy existed between the Diamantina and Kermadec trenches; Rhodobacterales' evolutionary adaptation related to genomic features (pN/pS and SNVs/kbp) in the deep-sea trench environments. These findings provided new insights into the community succession and potential adaption mechanism along the water columns to sediments in deep trenches.

SUBMITTER: Xiao Y 

PROVIDER: S-EPMC12822011 | biostudies-literature | 2025 Dec

REPOSITORIES: biostudies-literature