Metagenomics Evidence of a Novel Thermoplasmata-like\nArchaeon Decomposing Heterodisulfide in Nonacidic Estuary-Ocean Sediment

Thermoplasmata archaea,\nrenowned for their acidophilic and thermophilic\ntraits, have been implicated in methanogenic metabolism across diverse\nenvironments. However, their metabolic capabilities in nonacidic settings\nremain understudied. This metagenomic investigation unveils the microbiome\ndynamics and metabolic processes within nonacidic estuary-ocean sediments\nacross 19 sites (seven groups) in the Pearl River Estuary and South\nChina Sea regions. Remarkably, the microbiomes exhibited rapid adaptation\nand compositional consistency despite spatial heterogeneity, suggesting\nthe overriding influences of salinity, pH, and nutrient availability.\nMetabolic pathway reconstruction revealed prevalent modules for amino\nacid, nucleotide, lipid, vitamin, and carbohydrate metabolism, indicating\ncommunity adaptation to this environment. Additionally, the high occurrence\nof heterodisulfide reductase (<i>hdrA</i>) genes implicated\npotential roles in CoM-S-S-CoB degradation. Notably, we discovered\na novel Thermoplasmata-like genome (MAG3 in g3) that, despite sharing\ncore genomic traits with known Thermoplasmata, harbored distinct genetic\nvariabilities. Phylogenetic evidence robustly affiliated the Thermoplasmata-like\narchaeon with methanogenesis pathways, suggesting its potential involvement\nin CoM-S-S-CoB degradation under nonacidic conditions. This study\nenhances the understanding of microbiome composition and metabolic\nprocesses and highlights the pivotal contribution of Thermoplasmata\narchaea to sulfur cycling within nonacidic estuarine-ocean sediments.