Meta-Omics Approaches Reveal Unique Small RNAs Exhibited by the Uncultured Microorganisms Dwelling Deep-Sea Hydrothermal Sediment in Guaymas Basin

Small regulatory RNAs (sRNAs) are present in almost all investigated microbes, regarded as modulators and regulators of gene expression and also known to play their regulatory role in the environmentally significant process. It has been estimated that less than 1% of the microbes in nature are culturable in the laboratory, hindering our understanding of their physiology, and living strategies. However, recent big advancing of DNA sequencing and omics-related data analysis makes the understanding of the genetics, metabolic potentials, even ecological roles of uncultivated microbes possible. In this study, we used a metagenome and metatranscriptome based integrated approach to identifying small RNAs in the microbiome of Guaymas Basin sediments. Hundreds of environmental sRNAs comprising of 228 groups were identified based on their homology, 82% of which displayed high similarity with previously known small RNAs in Rfam database, whereas, “18%” are putative novel sRNA motifs. A putative cis-acting sRNA potentially binding to methyl coenzyme M reductase, a key enzyme in methanogenesis or anaerobic oxidation of methane (AOM), was discovered in the genome of ANaerobic MEthane oxidizing archaea group 1 (ANME-1), which were the dominate microbe in the sample. These sRNAs were actively expressed in local Guaymas Basin hydrothermal environment, suggesting important roles of sRNAs in regulating microbial activity in natural environments.