Comparative metagenomics reveals insights into the deep-sea adaptation mechanism of the microorganisms in Iheya hydrothermal fields.

In this study, comparative metagenomic analysis was performed to investigate the genetic profiles of the microbial communities inhabiting the sediments surrounding Iheya North and Iheya Ridge hydrothermal fields. Four samples were used, which differed in their distances from hydrothermal vents. The results showed that genes involved in cell surface structure synthesis, polyamine metabolism and homeostasis, osmoadaptation, pH and Na+ homeostasis, and heavy-metal transport were abundant. Pathways for putrescine and spermidine synthesis and transport were identified in the four metagenomes, which possibly participate in the regulation of cytoplasmic pH. Genes involved in the transport of K+ and the biosynthesis of glycine betaine, proline, and trehalose, together with genes encoding mechanosensitive channel of small conductance, were contributors of osmoadaptation. Detection of genes encoding F1Fo-ATPase and cation/proton antiporters indicated critical roles played by pH and sodium homeostasis. Cu2+-exporting and Cd2+/Zn2+-exporting ATPases functioned in the expulsion of toxic metals across cellular membranes. It is noteworthy that the distribution of some genes, such as that encoding cardiolipin synthase, was apparently affected by distance to the vent site. These findings provide insight into microbial adaptation mechanisms in deep-sea sediment environments.