Comparative Metagenomic Analysis of Two Hot Springs From Ourense (Northwestern Spain) and Others Worldwide

Abstract

With their circumneutral pH and their moderate temperature (66 and 68°C, respectively), As Burgas and Muiño da Veiga are two important human-use hot springs, previously studied with traditional culture methods, but never explored with a metagenomic approach. In the present study, we have performed metagenomic sequence-based analyses to compare the taxonomic composition and functional potential of these hot springs. Proteobacteria, Deinococcus-Thermus, Firmicutes, Nitrospirae, and Aquificae are the dominant phyla in both geothermal springs, but there is a significant difference in the abundance of these phyla between As Burgas and Muiño da Veiga. Phylum Proteobacteria dominates As Burgas ecosystem while Aquificae is the most abundant phylum in Muiño da Veiga. Taxonomic and functional analyses reveal that the variability in water geochemistry might be shaping the differences in the microbial communities inhabiting these geothermal springs. The content in organic compounds of As Burgas water promotes the presence of heterotrophic populations of the genera Acidovorax and Thermus, whereas the sulfate-rich water of Muiño da Veiga favors the co-dominance of genera Sulfurihydrogenibium and Thermodesulfovibrio. Differences in ammonia concentration exert a selective pressure toward the growth of nitrogen-fixing bacteria such as Thermodesulfovibrio in Muiño da Veiga. Temperature and pH are two important factors shaping hot springs microbial communities as was determined by comparative analysis with other thermal springs.

Keywords: extreme environments; hot springs; metagenomics; microbial communities; next generation sequencing; thermophiles.

FIGURE 1

Details of As Burgas and Muiño Da Veiga hot springs. Geographical location (A), As Burgas water spout (B), and Muiño da Veiga water pump (C).

FIGURE 2

Comparative taxonomic profile of BW and MDV at domain level.

FIGURE 3

Comparative taxonomic profile of BW and MDV at phylum level. Only phylum with significant biological differences (p < 0.05, difference between proportions >1% and twofold of ratio between proportions, STAMP) were represented.

FIGURE 4

Comparative taxonomic profile of BW and MDV at class level. Only classes with significant biological differences (p < 0.05, difference between proportions >1% and twofold of ratio between proportions, STAMP) were represented.

FIGURE 5

Comparative microbial diversity at different hot springs at domain level. Chart was generated using microbial abundance data. Each chart represents the percentage of abundance of each microbial group in a specific spring. Abundance values are generated from normalized data retrieved from MG-RAST.

FIGURE 6

Comparative microbial diversity within Bacteria domain at phylum level. Others include those phyla with less than 0.3% sequences annotated in the eight metagenomes: Candidatus Poribacteria, Chrysiogenetes, Elusimicrobia, Fibrobacteres, Lentisphaerae, Tenericutes, and Fusobacteria.

FIGURE 7

Comparative functional profile of BW and MDV at level 1 of the SEED subsystems. Only subsystems with significant biological differences (p < 0.05, difference between proportions >1% and twofold ratio between proportions, STAMP) were represented.

FIGURE 8

Comparative functional diversity at level 1. Others include those subsystems with less than 2% sequences annotated in the eight metagenomes: Cell division and cell cycle, dormancy and sporulation, iron acquisition and metabolism, metabolism of aromatic compounds, motility and chemotaxis, phosphorus metabolism, photosynthesis, potassium metabolism, regulation and cell signaling, secondary metabolism, and sulfur metabolism.