Nitrincola tapanii sp. nov., a novel alkaliphilic bacterium from An Indian Soda Lake

Absence of oxygen effect on microbial structure and methane production during drying and rewetting events

Natural environments with frequent drainage experience drying and rewetting events that impose fluctuations in water availability and oxygen exposure. These relatively dramatic cycles profoundly impact microbial activity in the environment and subsequent emissions of methane and carbon dioxide. In this study, we mimicked drying and rewetting events by submitting methanogenic communities from strictly anaerobic environments (anaerobic digestors) with different phylogenetic structures to consecutive desiccation events under aerobic (air) and anaerobic (nitrogen) conditions followed by rewetting. We showed that methane production quickly recovered after each rewetting, and surprisingly, no significant difference was observed between the effects of the aerobic or anaerobic desiccation events. There was a slight change in the microbial community structure and a decrease in methane production rates after consecutive drying and rewetting, which can be attributed to a depletion of the pool of available organic matter or the inhibition of the methanogenic communities. These observations indicate that in comparison to the drying and rewetting events or oxygen exposure, the initial phylogenetic structure and the organic matter quantity and quality exhibited a stronger influence on the methanogenic communities and overall microbial community responses. These results change the current paradigm of the sensitivity of strict anaerobic microorganisms to oxygen exposure.

Microbial community of soda Lake Van as obtained from direct and enriched water, sediment and fish samples

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.

Nitrincola iocasae sp. nov., a bacterium isolated from sediment collected at a cold seep field in the South China Sea

A novel bacterium, designated strain KXZD1103^T, was isolated from sediment collected at a cold seep field of the Formosa Ridge in the South China Sea. Cells were Gram-stain-negative, facultatively anaerobic, motile, oxidase- and catalase-positive, and grew optimally at 28 °C, pH 6.0-pH 7.0 and in the presence of 1-3 % (w/v) NaCl. The major cellular fatty acids were summed feature 8 (C_18 : 1  ω7c/C_18 : 1  ω6c), summed feature 3 (C_16 : 1  ω7c/C_16 : 1  ω6c) and C_16 : 0. The major respiratory ubiquinone was Q-8. The predominant polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. Analysis of 16S rRNA gene sequences revealed that strain KXZD1103^T grouped with members of the genus Nitrincola, with Nitrincola lacisaponensis 4CA^T (98.1 % sequence similarity) and Nitrincola schmidtii R4-8^T (97.7 %) as its closest neighbours. Genome sequencing revealed a genome size of 4.17 Mb and a DNA G+C content of 50.1 %. Genomic average nucleotide identity values for strain KXZD1103^T with the type strains within the genus Nitrincola ranged from 71.0 to 75.7 %, while the in silico DNA-DNA hybridization values for strain KXZD1103^T with these strains ranged from 16.1 to 21.6 %. On the basis of the results of phylogenetic, phenotypic and chemotaxonomic analyses, strain KXZD1103^T is considered to represent a novel species of the genus Nitrincola, for which the name Nitrincola iocasae sp. nov. is proposed. The type strain is KXZD1103^T (=KCTC 72678^T=MCCC 1K04283^T).