Microbial diversity in a submarine carbonate edifice from the serpentinizing hydrothermal system of the Prony Bay (New Caledonia) over a 6-year period.

Linda Guentas-Dombrowsky,Nan Mei,Anne Postec,Gaël Erauso,Martine Gérard,Bénédicte Ménez,Bernard Pelletier,Claude Payri,Méline Bes,Fatma Benaïssa,Christophe Monnin,Bernard Ollivier,Emmanuelle Gérard,Marianne Quéméneur,Céline Pisapia

doi:10.3389/fmicb.2015.00857

Abstract

Active carbonate chimneys from the shallow marine serpentinizing Prony Hydrothermal Field were sampled 3 times over a 6 years period at site ST09. Archaeal and bacterial communities composition was investigated using PCR-based methods (clone libraries, Denaturating Gel Gradient Electrophoresis, quantitative PCR) targeting 16S rRNA genes, methyl coenzyme M reductase A and dissimilatory sulfite reductase subunit B genes. Methanosarcinales (Euryarchaeota) and Thaumarchaea were the main archaeal members. The Methanosarcinales, also observed by epifluorescent microscopy and FISH, consisted of two phylotypes that were previously solely detected in two other serpentinitzing ecosystems (The Cedars and Lost City Hydrothermal Field). Surprisingly, members of the hyperthermophilic order Thermococcales were also found which may indicate the presence of a hot subsurface biosphere. The bacterial community mainly consisted of Firmicutes, Chloroflexi, Alpha-, Gamma-, Beta-, and Delta-proteobacteria and of the candidate division NPL-UPA2. Members of these taxa were consistently found each year and may therefore represent a stable core of the indigenous bacterial community of the PHF chimneys. Firmicutes isolates representing new bacterial taxa were obtained by cultivation under anaerobic conditions. Our study revealed diverse microbial communities in PHF ST09 related to methane and sulfur compounds that share common populations with other terrestrial or submarine serpentinizing ecosystems.

Highlights

Serpentinization is the process of aqueous alteration of ultramafic rocks that releases hydrogen (H2), methane (CH4), small organic compounds, and generates alkaline fluids with pH values commonly above pH 10, at reducing conditions (McCollom, 2007; Schrenk et al, 2013)
The Lost City Hydrothermal Field (LCHF) located at a depth of about 800 m below sea level on the top of the Atlantis massif at 30◦N near the Mid-Atlantic Ridge is to date the most extensively studied submarine site driven by active serpentinization
This study provides a detailed description of the microbial communities from carbonate samples collected at an underwater site of the Prony hydrothermal field between 2005 and 2011

Summary

Introduction

Serpentinization is the process of aqueous alteration of ultramafic rocks that releases hydrogen (H2), methane (CH4), small organic compounds, and generates alkaline fluids with pH values commonly above pH 10, at reducing conditions (McCollom, 2007; Schrenk et al, 2013) This last decade, low temperature serpentinizing environments have attracted much scientific interest because they are considered as analogs of those from which life may have arisen on the early Earth. Bacterial sulfate reducers (namely Desulfotomaculum) were identified while microbial H2 production by anaerobic Clostridiales was evidenced by metagenomics (Brazelton et al, 2012)

Methods

Results

Conclusion