Abstract
Little is known about the functional capability of microbial communities in shallow-sea hydrothermal systems (water depth of <200 m). This study analyzed two high-throughput pyrosequencing metagenomic datasets from the vent and the surface water in the shallow-sea hydrothermal system offshore NE Taiwan. This system exhibited distinct geochemical parameters. Metagenomic data revealed that the vent and the surface water were predominated by Epsilonproteobacteria (Nautiliales-like organisms) and Gammaproteobacteria ( Thiomicrospira -like organisms), respectively. A significant difference in microbial carbon fixation and sulfur metabolism was found between the vent and the surface water. The chemoautotrophic microorganisms in the vent and in the surface water might possess the reverse tricarboxylic acid cycle and the Calvin−Bassham−Benson cycle for carbon fixation in response to carbon dioxide highly enriched in the environment, which is possibly fueled by geochemical energy with sulfur and hydrogen. Comparative analyses of metagenomes showed that the shallow-sea metagenomes contained some genes similar to those present in other extreme environments. This study may serve as a basis for deeply understanding the genetic network and functional capability of the microbial members of shallow-sea hydrothermal systems.
Highlights
The discovery of deep-sea hydrothermal vents in the late 1970s expanded our knowledge of the extent of microhabitats for microorganisms and the possible origins of life on Earth [1,2]
Functional gene analyses showed that species belonging to Gammaproteobacteria and Epsilonproteobacteria in deep-sea hydrothermal vent ecosystems have the potential to grow chemoautotrophically through the Calvin-Benson-Bassham (CBB) cycle and the reductive tricarboxylic acid cycle, respectively [5,19]
Compared with deep-sea vents, shallow hydrothermal systems are characterized by the presence of a gas phase and the enrichment of O2 [7]
Summary
The discovery of deep-sea hydrothermal vents in the late 1970s expanded our knowledge of the extent of microhabitats for microorganisms and the possible origins of life on Earth [1,2]. Functional gene analyses showed that species belonging to Gammaproteobacteria and Epsilonproteobacteria in deep-sea hydrothermal vent ecosystems have the potential to grow chemoautotrophically through the Calvin-Benson-Bassham (CBB) cycle and the reductive tricarboxylic acid (rTCA) cycle, respectively [5,19].
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