Soda lakes are saline and alkaline ecosystems that are considered to have existed since the first geological records of the world. These lakes support the growth of ecologically and economically important microorganisms due to their unique geochemistry. Microbiota members of lakes are valuable models to study the link between community structure and abiotic parameters such as pH and salinity. Lake Van is the largest endroheic lake and in this study, bacterial diversity of lake water, sediment, and pearl mullet (inci kefali; Alburnus tarichi), an endemic species of fish which are collected from different points of the lake, are studied directly and investigated meticulously using a metabarcoding approach after pre-enrichment. Bacterial community structures were identified using Next Generation Sequencing of the 16S rRNA gene. The analysis revealed that the samples of Lake Van contain high level of bacterial diversity. Direct water samples were dominated by Proteobacteria, Cyanobacteria, and Bacteroidota, on the other hand, pre-enriched water samples were dominated by Proteobacteria and Firmicutes at phylum-level. In direct sediment samples Proteobacteria, whereas in pre-enriched sediment samples Firmicutes and Proteobacteria were determined at highest level. Pre-enriched fish samples were dominated by Proteobacteria and Firmicutes at phylum-level. In this study, microbiota members of Lake Van were identified by taxonomic analysis.

Arsenic is responsible for water pollution in many places around the world and presents a serious health risk for people. Lake Van is the world’s largest soda lake, and there are no studies on seasonal arsenic pollution and arsenic-resistant bacteria. We aimed to determine the amount of arsenic in the lake water and sediment, to isolate arsenic-metabolizing anaerobic bacteria and their identification, and determination of arsenic metabolism. Sampling was done from 7.5 m to represent the four seasons. Metal contents were determined by using ICP-MS. Pure cultures were obtained using the Hungate technique. Growth characteristics of the strains were determined at different conditions as well as at arsenate and arsenite concentrations. Molecular studies were also carried out for various resistance genes. Our results showed that Lake Van’s total arsenic amount changes seasonally. As a result of 16S rRNA sequencing, it was determined that the isolates were members of 8 genera with arsC resistance genes. In conclusion, to sustain water resources, it is necessary to prevent chemical and microorganism-based pollution. It is thought that the arsenic-resistant bacteria obtained as a result of this study will contribute to the solution of environmental arsenic pollution problems, as they are the first data and provide the necessary basic data for the bioremediation studies of arsenic from contaminated environmental habitats. At the same time, the first data that will contribute to the creation of the seasonal arsenic map of Lake Van are obtained.

Extensive arsenic contamination of groundwater, rivers, and agricultural farms has led to widespread arsenic poisoning and consequent problems associated with health and economy. In recent years, many studies have been performed to understand bacterial arsenic detoxification and metabolism which has paved the way for bioremediation applications. This study attempted to isolate and characterize arsenic-resistant bacteria from the drying Urmia lake. As a result of the 16S rDNA analysis, six arsenic-resistant strains were identified as the members of Shouchella, Salipaludibacillus, and Evansella genera. For some of the strains, the maximum tolerance concentration for either arsenate or arsenite was considerably high, 320 and 16 mM, respectively. All the strains harbored the arsenate reductase gene (arsC). The arsenate permease (arsB) gene was identified in all strains except in strains S1, S12, and E15. The metabolic genes of respiratory arsenate reductase (arrB) and arsenite oxidase (arxA) were identified in none of these strains. This feature of the strains with the arsC gene region can be exploited to bioremediate arsenic from contaminated areas by using a two-step process. The second step can be carried out by the adsorption of arsenite to iron oxide or by precipitation with sulfide. Today, more and more ecosystems are being destroyed due to anthropogenic pollution, and it is important to reveal the negative effects and solutions of this situation on the ecosystems. So, the current study provides a potential source of bacteria for such studies that implement bioremediation practices to prevent arsenic catastrophe in vicinal territories, and reveals arsenic pollution in Urmia lake.

Determination of the Genetic Diversity of Different Bioluminescent Bacteria by Pulsed-Field Gel Electrophoresis (PFGE) - Jundishapur Journal of Microbiology - - Kowsar