Sulfur metabolizing microbes dominate microbial communities in Andesite-hosted shallow-sea hydrothermal systems

Abstract

To determine microbial community composition, community spatial structure and possible key microbial processes in the shallow-sea hydrothermal vent systems off NE Taiwan's coast, we examined the bacterial and archaeal communities of four samples collected from the water column extending over a redoxocline gradient of a yellow and four from a white hydrothermal vent. Ribosomal tag pyrosequencing based on DNA and RNA showed statistically significant differences between the bacterial and archaeal communities of the different hydrothermal plumes. The bacterial and archaeal communities from the white hydrothermal plume were dominated by sulfur-reducing Nautilia and Thermococcus, whereas the yellow hydrothermal plume and the surface water were dominated by sulfide-oxidizing Thiomicrospira and Euryarchaeota Marine Group II, respectively. Canonical correspondence analyses indicate that methane (CH(4)) concentration was the only statistically significant variable that explains all community cluster patterns. However, the results of pyrosequencing showed an essential absence of methanogens and methanotrophs at the two vent fields, suggesting that CH(4) was less tied to microbial processes in this shallow-sea hydrothermal system. We speculated that mixing between hydrothermal fluids and the sea or meteoric water leads to distinctly different CH(4) concentrations and redox niches between the yellow and white vents, consequently influencing the distribution patterns of the free-living Bacteria and Archaea. We concluded that sulfur-reducing and sulfide-oxidizing chemolithoautotrophs accounted for most of the primary biomass synthesis and that microbial sulfur metabolism fueled microbial energy flow and element cycling in the shallow hydrothermal systems off the coast of NE Taiwan.

Figure 1. Chemical parameters along the vertical gradients of the yellow (YV) and white (WV) hydrothermal vent plumes.

Figure 2. NMDS ordination of the Bray-Curtis similarities in bacterial or archaeal community composition.

(A) bacterial DNA-based libraries. (B) bacterial RNA-based libraries. (C) archaeal DNA-based libraries. (D) archaeal RNA-based libraries. Each point represents an individual sample. Circles separate different clusters. ANOSIM analysis shows that the observed cluster patterns are significant.

Figure 3. UPGMA trees constructed from Thetayc distances between bacterial libraries (A) and Bray-Curtis distances between archaeal libraries (B).

Figure 4. CCA (A, C and D) or RDA (B) analyses of bacterial or archaeal communities.

(A) bacterial DNA-based libraries. (B) bacterial RNA-based libraries. (C) archaeal DNA-based libraries. (D) archaeal RNA-based libraries. Each point represents an individual sample. Arrowheads represent statistically significant environmental variables explaining the observed patterns (P = 0.002). CH4: methane. Temp: temperature. DOC: dissolved organic carbon.

Figure 5. Distribution of tags by phylogenetic taxa among the bacterial DNA- (A-D) and RNA-based libraries (E-H).

(A) and (E) Relative abundances of bacterial phyla or classes in total tags of each library. (B) and (F) Relative abundance of bacterial genera in total gammaproteobacterial tags. (C) and (G) Relative abundance of bacterial genera in total epsilonproteobacterial tags. (D) and (H) Relative abundance of bacterial families in total alphaproteobacterial tags.

Figure 6. Distribution of tags by phylogenetic taxa among the archaeal DNA- (A) and RNA-based libraries (B).