Prokaryotic diversity and biogeochemical characteristics of field living and laboratory cultured stromatolites from the hypersaline Laguna Interna, Salar de Atacama (Chile).

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.

Diversity of microbial community and its metabolic potential for nitrogen and sulfur cycling in sediments of Phu Quoc island, Gulf of Thailand.

Although Phu Quoc island, Gulf of Thailand possesses diverse marine and coastal ecosystems, biodiversity and metabolic capability of microbial communities remain poorly investigated. The aim of our study was to evaluate the biodiversity and metabolic potential of sediment microbial communities in Phu Quoc island. The marine sediments were collected from three different areas and analyzed by using 16S rRNA gene-based amplicon approach. A total of 1,143,939 reads were clustered at a 97% sequence similarity into 8,331 unique operational taxonomic units, representing 52 phyla. Bacteria and archaea occupied averagely around 86% and 14%, respectively, of the total prokaryotic community. Proteobacteria, Planctomycetes, Chloroflexi, and Thaumarchaeota were the dominant phyla in all sediments, which were involved in nitrogen and sulfur metabolism. Sediments harboring of higher nitrogen sources were found to coincide with increased abundance of archaeal phylum Thaumarchaeota. Predictive functional analysis showed high abundance prokaryotic genes associated with nitrogen cycling including nifA-Z, amoABC, nirA, narBIJ, napA, nxrAB, nrfA-K, nirBD, nirS, nirK, norB-Z, nlnA, ald, and ureA-J, based on taxonomic groups detected by 16S rRNA sequencing. Although the key genes involved in sulfur cycling were found to be at low to undetectable levels, the other genes encoding for sulfur-related biological processes were present, suggesting that alternative pathways may be involved in sulfur cycling at our study site. In conclusion, our study for the first time shed light on diversity of microbial communities in Phu Quoc island.

Biogas from Tannery Solid Waste Anaerobic Digestion Is Driven by the Association of the Bacterial Order Bacteroidales and Archaeal Family Methanosaetaceae.

The search for renewable energies has been one of the biggest challenges of the last decades. Sludge and solid wastes of many sources have been used to produce biogas of high calorific value. Thus, this work aimed to evaluate the biogas production of solid waste originating from a tannery that uses chromium salts as a tanning agent and to characterize the physicochemical parameters and microbial composition of the biogas-producing biomass. Wastes were collected and the parameters were evaluated at the initial and final time points of the anaerobic incubation process. At the end of 150 days, there was a production of 26.1 mL g-1 VSS of biogas with 52% of methane. The highest amount of biomethane observed was related to the archaeal family Methanosaetaceae and bacterial order Bacteroidales. Knowledge about changes in the microbial composition can provide tools for manipulation, isolation, and inoculation of the microorganisms inside the bioreactors to maximize methane production.

Prokaryotic and eukaryotic community structure affected by the presence of an acid mine drainage from an abandoned gold mine.

The acid mine drainage that originates in the abandoned gold mine in San Luis, Argentina, is released into La Carolina stream. The aim of this study was to determine the influence of this mine drainage on the physicochemical parameters of the area studied and on both prokaryotic and eukaryotic community structure. In addition, specific relationships between microbial taxonomic groups and physicochemical parameters were established. The drainage that flows into La Carolina stream acidifies the stream and increases its sulfate, Zn, Cd and Te concentrations. Microbial analysis showed that prokaryotic community structure is mainly affected by pH values. Actinobacteria and Gammaproteobacteria were abundant in samples characterized by low pH values, while Nitrospirae, Chloroflexi, Deltaproteobacteria, Thaumarchaeota and Euryarchaeota were associated with high concentrations of heavy metals. Otherwise, Alphaproteobacteria was present in samples taken in sunlit areas. Regarding eukaryotic community structure, the sunlight had the greatest impact. Inside the mine, in the absence of light, fungi and protists members were the most abundant microorganisms, while those samples taken in the presence of light displayed algae (green algae and diatoms) as the most abundant ones. After receiving the mine drainage, the stream showed a decrease in the diatom abundance and green algae predominated.