Microbial Community Structure in a Serpentine-Hosted Abiotic Gas Seepage at the Chimaera Ophiolite, Turkey

The surface waters at the ultramafic ophiolitic outcrop in Chimaera, Turkey, are characterized by high pH values and high metal levels due to the percolation of fluids through areas of active serpentinization. We describe the influence of the liquid chemistry, mineralogy, and H 2 and CH 4 levels on the bacterial community structure in a semi-dry, exposed ultramafic environment. The bacterial and archaeal community structures were monitored using Illumina sequencing targeting the16S rRNA gene. At all sampling points, four phyla, Proteobacteria , Actinobacteria , Chloroflexi and Acidobacteria , accounted for the majority of taxa. Chloroflexi dominated low-diversity sites, whereas Proteobacteria dominated high-diversity sites. Methane, nitrogen, iron and hydrogen oxidizers were detected as well as archaea and metal-resistant bacteria. Importance: Our study is a comprehensive microbial investigation of the Chimaera ophiolite. DNA has been extracted from 16 sites in the area and has been studied from a microbial and geochemical point of view. We describe a microbial community structure that is dependent on terrestrial, serpentinization-driven abiotic H 2 , which is poorly studied due to the rarity of these environments on Earth.