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Stromatolites are organo-sedimentary structures found principally in seas and saline lakes that contain sheets of sediments and minerals formed by layers of microbial communities, which trap sediments and induce the precipitation of minerals.A living stromatolite from the alkaline Laguna Interna in the Salar de Atacama was collected and one of the fragments was deposited in an experimental aquarium for 18 months. We used Illumina sequencing of PCR-amplified V4 regions of 16S rRNA genes from total extracted DNA to identify the microbial populations. The chemical structure was studied using X-Ray Diffraction (XRD) and bench chemical methods. We found that members belonging to the Proteobacteria, Planctomycetes, Chloroflexi and Bacteroidetes phyla dominated the bacterial communities of the living and aquarium cultured samples. The potential metabolic functionality of the prokaryotic community reveals that sulfur, nitrogen, methane and carbon fixation metabolism functions are present in the samples. This study is the first to provide new insights into the prokaryotic community composition from this unusual aquatic desert site. Further studies will be helpful to obtain a better understanding of the biotic and abiotic mechanisms residing in stromatolites from Laguna Interna, as well as to have better knowledge about the formation of these biosignatures.

Salinity is an important environmental factor influencing microbial community composition. To better understand this influence, we determined the bacterial communities present in 17 different sites of brackish sediment (underwater) and soil (surface) samples from the Camargue region (Rhône river delta) in southern France during the fall of 2013 and 2014 using pyrosequencing of the V3-V4 regions of the 16S rRNA genes amplified by PCR. This region is known for abundant flora and fauna and, though saline, 30% of rice consumed in France is grown here. We found that bacterial abundance in 1 g of soil or sediment, calculated by qPCR, was higher in sediments than in surface soil samples. Members belonging to the Proteobacteria, Bacteroidetes, Chloroflexi and Firmicutes phyla dominated the bacterial communities of sediment samples, while members belonging to the Proteobacteria, Bacteroidetes, Gemmatimonadetes, Actinobacteria, Firmicutes and Acidobacteria phyla dominated the bacterial communities of the soil samples. The most abundant bacterial genera present in the saline sediments and soils from the Camargue belonged mostly to halophilic and sulphate reducing bacteria, suggesting that the Camargue may be a valuable system to investigate saline, yet agriculturally productive, sediment and soil microbial ecosystem.

The aim of this study was to compare the composition of two deep-sea viral communities obtained from the Romanche Fracture Zone in the Atlantic Ocean (collected at 5200 m depth) and the southwest Mediterranean Sea (from 2400 m depth) using a pyro-sequencing approach. The results are based on 18.7% and 6.9% of the sequences obtained from the Atlantic Ocean and the Mediterranean Sea, respectively, with hits to genomes in the non-redundant viral RefSeq database. The identifiable richness and relative abundance in both viromes were dominated by archaeal and bacterial viruses accounting for 92.3% of the relative abundance in the Atlantic Ocean and for 83.6% in the Mediterranean Sea. Despite characteristic differences in hydrographic features between the sampling sites in the Atlantic Ocean and the Mediterranean Sea, 440 virus genomes were found in both viromes. An additional 431 virus genomes were identified in the Atlantic Ocean and 75 virus genomes were only found in the Mediterranean Sea. The results indicate that the rather contrasting deep-sea environments of the Atlantic Ocean and the Mediterranean Sea share a common core set of virus types constituting the majority of both virus communities in terms of relative abundance (Atlantic Ocean: 81.4%; Mediterranean Sea: 88.7%).

Arid regions represent nearly 30 % of the Earth's terrestrial surface, but their microbial biodiversity is not yet well characterized. The surface sands of deserts, a subset of arid regions, are generally subjected to large temperature fluctuations plus high UV light exposure and are low in organic matter. We examined surface sand samples from the Taklamaken (China, three samples) and Gobi (Mongolia, two samples) deserts, using pyrosequencing of PCR-amplified 16S V1/V2 rDNA sequences from total extracted DNA in order to gain an assessment of the bacterial population diversity. In total, 4,088 OTUs (using ≥97 % sequence similarity levels), with Chao1 estimates varying from 1,172 to 2,425 OTUs per sample, were discernable. These could be grouped into 102 families belonging to 15 phyla, with OTUs belonging to the Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria phyla being the most abundant. The bacterial population composition was statistically different among the samples, though members from 30 genera were found to be common among the five samples. An increase in phylotype numbers with increasing C/N ratio was noted, suggesting a possible role in the bacterial richness of these desert sand environments. Our results imply an unexpectedly large bacterial diversity residing in the harsh environment of these two Asian deserts, worthy of further investigation.

To better understand microbial populations present in atypical soil environments, and to discern any relations between these environments and their bacterial communities, we examined the “Padza de Dapani” on the island of Mayotte off the east coast of Africa. This area is not a true (hot) desert, but resembles one in many places due to extensive soil erosion. We collected surface soil samples from five different sites of the Padza de Dapani in Mayotte. We examined bacterial biodiversity using pyrosequencing of PCR-amplified 16S V1-V3 rDNA sequences from total extracted DNA. Our results show that in the acidic (pH 4.6-6), oligotrophic (organic carbon; 0.1-0.7 g/kg of soil) and mineralized (Fe: 18 g/100 g; Al: 12 g/100 g) Dapani Padza soil samples, members of the Actinobacteria and Proteobacteria phyla dominated the bacterial communities, as was also observed in samples from Saudi Arabia hot desert sands.Interestingly, members belonging to the genera Acinetobacter, Arthrobacter and Bacillus were also found to be very abundant in our samples. These were also seen in hot Asian deserts sand samples, such as those from the Gobi (Mongolia) and Taklamaken (China) deserts, thus possibly pointing to microbial populations characteristic of denuded soils. [ABSTRACT FROM AUTHOR]

Desert-like areas located in the eastern portion of the state of Utah (USA) have geographic features that can resemble the surface of the planet Mars, characterized by red-colored hills, soils and sandstones. We examined the bacterial biodiversity of surface soil samples from several sites from the Colorado Plateau Desert in eastern Utah using pyrosequencing of PCR amplified bacterial 16S rRNA genes from total extracted soil DNA. The sample sites cover the Great Basin, Goblin Valley State Park and nearby regions on the Colorado Plateau. We also examined several physicochemical parameters of the soil samples to investigate any possible correlations between bacterial community structure and environmental drivers. The predominant bacterial phyla present in the samples were found to belong to members of the Proteobacteria, Actinobacteria, Bacteroidetes, and Gemmatimonadetes. The most abundant genera in our samples were found to belong to the Cesiribacter, Lysobacter, Adhaeribacter, Microvirga and Pontibacter genera. We found that the relative abundance of Proteobacteria and Gemmatimonadetes were significantly correlated with soil pH and a low concentration of organic matter, suggesting that, in these relatively high-altitude desert soils, these two parameters may be of primary importance to influence bacterial community composition. [ABSTRACT FROM AUTHOR]