PeatlandAcidobacteriawith a dissimilatory sulfur metabolism

Abstract

AbstractSulfur-cycling microorganisms impact organic matter decomposition in wetlands and consequently greenhouse gas emissions from these globally relevant environments. However,their identities and physiological properties are largely unknown. By applying a functional metagenomics approach to an acidic peatland, we recovered draft genomes of seven novelAcidobacteriaspecies with the potential for dissimilatory sulfite (dsrAB,dsrC,dsrD,dsrN, dsrT, dsrMKJOP) or sulfate respiration (sat, aprBA, qmoABCplusdsrgenes). Surprisingly, the genomes also encodeddsrL, a unique gene of the sulfur oxidation pathway. Metatranscriptome analysis demonstrated expression of acidobacterial sulfur-metabolism genes in native peat soil and their upregulation in diverse anoxic microcosms. This indicated an active sulfate respiration pathway, which, however, could also operate in reverse for sulfur oxidation as recently shown for other microorganisms.Acidobacteriathat only harbored genes for sulfite reduction additionally encoded enzymes that liberate sulfite from organosulfonates, which suggested organic sulfur compounds as complementary energy sources. Further metabolic potentials included polysaccharide hydrolysis and sugar utilization, aerobic respiration, several fermentative capabilities, and hydrogen oxidation. Our findings extend both, the known physiological and genetic properties ofAcidobacteriaand the known taxonomic diversity of microorganisms with a DsrAB-based sulfur metabolism, and highlight new fundamental niches for facultative anaerobicAcidobacteriain wetlands based on exploitation of inorganic and organic sulfur molecules for energy conservation.