Inter-comparison of the potentially active prokaryotic communities in the halocline sediments of Mediterranean deep-sea hypersaline basins

Abstract

The sediment microbiota of the Mediterranean deep--sea anoxic hypersaline basins (DHABs) are understudied relative to communities in the brines and halocline waters. In this study, the active fraction of the prokaryotic community in the halocline sediments of L' Atalante, Urania and Discovery DHABs was investigated based on extracted total RNA and 454 pyrosequencing of the 16S rRNA gene. Bacterial and archaeal communities were different in the sediments underlying the halocline waters of the three habitats, reflecting the unique chemical settings of each basin. The relative abundance of unique operational taxonomic units (OTUs) was also different between deep--sea control sediments and sediments underlying DHAB haloclines, suggesting adaptation to the steep DHAB chemical gradients. Only a few OTUs were affiliated to known bacterial halophilic and/or aerobic groups. Many OTUs, including some of the dominant ones, were related to aerobic taxa. Archaea were detected only in few halocline samples, with lower OTU richness relative to Bacteria, and were dominated by taxa associated with methane cycling. This study suggests that while metabolically active prokaryotic communities appear to be present in sediments underlying the three DHABs investigated, their diversity and activity are likely to be more reduced in sediments underlying the brines.3

Gene expression profiling of microbial activities and interactions in sediments under haloclines of E. Mediterranean deep hypersaline anoxic basins

“…Our DUH dataset was comprised primarily of rRNA sequences of Pseudoalteromonas sp., Clostridia and the family Flavobacteraceae. Consistent with this, Kormas et al (2015) found a Clostridium-like phylotype to dominate DUH sediments. In the DLH sample, sequences affiliating to Pseudoalteromonas sp.…”

“…Our previous study of 16S rRNA diversity in sediments from the same cores analyzed here (Kormas et al, 2015) indicated that DHAB environmental factors significantly shaped microbial communities. In that contribution, archaeal operational taxonomic units were detected only in few halocline samples.…”

“…Archaeal signatures were dominated by taxa associated with methane-rich deep-sea sediments, but might not be directly involved in methanogenesis/anaerobic oxidation of methane because we did not detect transcripts of methyl coenzyme M-reductase. Kormas et al (2015) found each site harbored only a few site-specific dominant bacterial operational taxonomic units that included members of α-, βand γ-Proteobacteria, Firmicutes, Actinobacteria and the Bacteroidetes/Chlorobi group, with most operational taxonomic units in lower haloclines related to halotolerant taxa or phylotypes described from high-salt habitats. We interpret taxonomic distributions of rRNA transcripts within our data sets with caution, as library preps can introduce biases, and preservation of rRNA of inactive/dead organisms under anoxic conditions has been reported (for example, Orsi et al, 2013).…”

Removal performance and microbial communities in a sequencing batch reactor treating hypersaline phenol-laden wastewater

“…The abundance of phylum Proteobacteria was enhanced in Y2, which might be due to the increase of salinity. This could also be found in the study of13 Luo et al,(2016). With regard to Sample Y1, the phyla of which the abundance ranked from second to sixth were Candidate division TM7 (10.99%), Actinobacteria (9.16%), Bacteroidetes (6.16%), Firmicutes (2.69%) and Deinococcus-Thermus (1.01%).…”

“…In some extreme environments such as hypersaline wastewater, metabolic potential of specific functional microorganisms plays an essential role in effective removal of pollutants (Kormas et al, 2015). Halomonas belong to Proteobacteria, some of which are capable of utilizing phenol as sole source of carbon and energy, which might contribute to phenol degradation in the present study.…”