Date Published: July 12, 2017
Publisher: Public Library of Science
Author(s): Hai-liang Wang, Jian Zhang, Qing-lei Sun, Chao Lian, Li Sun, Tzen-Yuh Chiang.
Currently, little is known about the microbial diversity in the sediments of Pacmanus and Desmos hydrothermal fields in Manus Basin. In this study, Illumina-based sequencing of 16S rRNA gene amplicons and metagenomic analysis were conducted to investigate the microbial populations and metabolic profiles in the sediments from four different regions in Pacmanus and Desmos hydrothermal fields. It was found that Gammaproteobacteria and Thaumarchaeota were the most abundant bacterial and archaeal populations, respectively. The autotrophic prokaryotes in the four communities probably fixed CO2 via four major pathways, i.e. Calvin-Benson-Bassham cycle, reductive acetyl-CoA cycle, rTCA cycle, and 3-hydroxypropionate/4-hydroxybutyrate cycle. Ammonia-oxidizing Thaumarchaeota, nitrifiers, denitrifiers, and sulfur oxidizers belonging to the subgroups of Proteobacteria (e.g., alpha, beta, gamma, and epsilon), Nitrospira, and Nitrospina, and sulfate-reducing Desulfobacterales likely played critical roles in nitrogen and sulfur cycling, in which ammonia, sulfur compounds, and hydrogen could be utilized as potential energy sources. These findings revealed new insights into the operational mechanism of the microbial communities associated with Pacmanus and Desmos hydrothermal fields.
Manus Basin is located behind the New Britain arc-trench system . Pacmanus, Desmos, and Susu Knolls are the three major hydrothermal fields in the eastern part of the basin [2,3]. The Pacmanus field in Pual Ridge was discovered in 1991, which consists of five discrete high-temperature hydrothermal sites (Roger’s Ruins, Roman Ruins, Satanic Mills, Tsukushi, and Fenway), a low-temperature diffuse vent site (Snowcap), and four new vent sites (Mimosa, Solwara 6, 7, and 8) [2–6]. The Snowcap area is heavily sedimented with hydrothermal precipitate/volcaniclastic debris and covered by bacterial mats [5,7]. In Fenway, a large black smoker chimney has been found to discharge the highest temperature fluids (358°C) observed at the Pacmanus field . Solwara 8 is located southeast of Fenway and hosts black smoker chimneys releasing high-temperature fluids .
In this study, we conducted the first investigation on microbial diversity and potential metabolic profiles of the microbial communities inhabiting the sediments of the hydrothermal fields in Pacmanus and Desmos. We found that all microbial communities were dominated by Proteobacteria, and that ammonia- and sulfur-oxidizing prokaryotes likely played essential roles in the cycling of nitrogen and sulfur as well as in CO2 fixation. Ammonia, reduced sulfur compounds, and hydrogen as potential important energy sources were possibly utilized to fuel the microbial communities. These first observations add new insights into the metabolisms of the microbes in deep-sea hydrothermal fields.