Y. Guan, T. Hikmawan, A. Antunes, D.K. Ngugi, U. Stingl
Research in Microbiology, pii: S0923-2508(15)00117-5, (2015)
Hypersaline environments, Brine pools, Biodiversity, Methanogens, Sulfate reducers
Oceanic deep hypersaline anoxic basins (DHABs) are characterized by
drastic changes in physico-chemical conditions in the transition from
overlaying seawater to brine body. Brine-seawater interfaces (BSIs) of
several DHABs across the Mediterranean Sea have been shown to possess
methanogenic and sulfate-reducing activities, yet no systematic studies
have been conducted to address the potential functional diversity of
methanogenic and sulfate-reducing communities in the Red Sea DHABs.
Here, we evaluated the relative abundance of Bacteria and Archaea using
quantitative PCR and conducted phylogenetic analyses of nearly
full-length 16S rRNA genes as well as functional marker genes encoding
the alpha subunits of methyl-coenzyme M reductase (mcrA) and dissimilatory sulfite reductase (dsrA). Bacteria predominated over Archaea in most locations, the majority of which were affiliated with Deltaproteobacteria, while Thaumarchaeota
were the most prevalent Archaea in all sampled locations. The upper
convective layers of Atlantis II Deep, which bear increasingly harsh
environmental conditions, were dominated by members of the class Thermoplasmata
(Marine Benthic Group E and Mediterranean Sea Brine Lakes Group 1). Our
study revealed unique microbial compositions, the presence of
niche-specific groups, and collectively, a higher diversity of
sulfate-reducing communities compared to methanogenic communities in all
five studied locations.