Microbial distribution in different spatial positions within the walls of a black sulfide hydrothermal chimney

Deep-sea hydrothermal chimneys encompass diverse niches for different microbial communities with steep environmental gradients. An active sulfide hydrothermal structure was recovered from the Dudley site of the Main Endeavour Field in the Juan de Fuca Ridge. Subsamples were taken from different spatial positions within the chimney wall and analyzed for mineral composition and microbial biomass and community structure to illustrate the characteristics of microbial distribution and environmental constraints. Mineral analysis showed that the chimney was mainly composed of various Fe-, Zn-, and Cu-rich sulfides, with mineral composition and abundance varying with spatial position. Microbial populations in the chimney predominantly consisted of archaeal members affiliated with the deep-sea hydrothermal vent Euryarchaeota group, Thermococcales, and Desulfurococcales, as well as bacterial members of the Gamma-, Epsilon-, and Deltaproteobacteria. Microbial biomass and composition shifted dramatically and formed different microbial zones within the chimney walls, from predominantly mesophilic, sulfur-oxidizing bacterial communities at the outer surfaces to thermophilic or hyperthermophilic, archaeal sulfur-reducers in the inner layers of the chimney. Based on microbial physiological characteristics and their distribution profiles, we inferred that temperature, fluid geochemistry, and organic compounds probably play an important role in selecting for and sustaining microbial communities. Furthermore, in situ temperature regimes within the chimney walls were roughly estimated based on the temperatures supporting the growth of the dominant microbial groups.