‘Candidatus Oscillochloris kuznetsovii’ a novel mesophilic filamentous anoxygenic phototrophic Chloroflexales bacterium from Arctic coastal environments

ABSTRACT Chloroflexales bacteria are mostly known as filamentous anoxygenic phototrophs that thrive as members of the microbial communities of hot spring cyanobacterial mats. Recently, we described many new Chloroflexales species from non-thermal environments and showed that mesophilic Chloroflexales are more diverse than previously expected. Most of these species were isolated from aquatic environments of mid-latitudes. Here, we present the comprehensive characterization of a new filamentous multicellular anoxygenic phototrophic Chloroflexales bacterium from an Arctic coastal environment (Kandalaksha Gulf, the White Sea). Phylogenomic analysis and 16S rRNA phylogeny indicated that this bacterium belongs to the Oscillochloridaceae family as a new species. We propose that this species be named ‘Candidatus Oscillochloris kuznetsovii’. The genomes of this species possessed genes encoding sulfide:quinone reductase, the nitrogenase complex and the Calvin cycle, which indicate potential for photoautotrophic metabolism. We observed only mesophilic anaerobic anoxygenic phototrophic growth of this novel bacterium. Electron microphotography showed the presence of chlorosomes, polyhydroxyalkanoate-like granules and polyphosphate-like granules in the cells. High-performance liquid chromatography also revealed the presence of bacteriochlorophylls a, c and d as well as carotenoids. In addition, we found that this bacterium is present in benthic microbial communities of various coastal environments of the Kandalaksha Gulf.

Mercury in White Sea bottom sediments: distribution, sources, and deposition chronology

For the first time, vertical and lateral distribution patterns of mercury in White Sea bottom sediments have been determined. An abrupt change in the nature of mercury concentrations has been revealed, with a general tendency to decrease with depth. Natural variations in mercury concentrations within 0.01 - 0.03 μg/g dry weight (dw) have been established. An upper value of 0.03 μg/g dw is taken for the natural background content of the element. The distribution of mercury concentrations in the sequence of bottom sediments is influenced by both anthropogenic and natural factors and processes. With distance from the marine -estuary boundary of the Northern Dvina River, the river’s role in supplying mercury to the White Sea is reduced, and global and regional atmospheric mass transfer take over. The mercury content is used as an indicator of landslide processes in Kandalaksha Gulf of the White Sea. The accumulation chronology of mercury in White Sea sediments is studied, and the proportion of anthropogenic mercury is calculated.

Characteristics of gas-saturated deposits of the Kandalaksha bay, the White Sea, according to the seismic-acoustic and litho-geochemical studies

The article discusses the results of complex geological, geophysical and geochemical studies of gas-saturated sediments within the Kandalaksha gulf, the White Sea. As a part of the marine study detailed seismoacoustic studies were conducted, resulting in the geometry of the seabed, the distribution of geological peculiarities of the sedimentary sequence, including the zones of focused unloading of hydrocarbon fluids. It is shown that assemblages of the «gas caps» are confined to the zones of maximal thickness of post-glacial sediments. The composition of the organic matter in the sediments and the gas phase has been studied in detail.

THE SEDIMENTARY COVER STRUCTURE OF THE KANDALAKSHA GULF OF THE WHITE SEA) ACCORDING TO CONTINUOUS SEISMIC PROFILING DATA

The geological structure of the water area adjacent to the White Sea biological research station of the Moscow State University (the Rugoserskaya bay and the Great Salma strait, the Kandalaksha gulf of the White Sea) was examined for the first time basing on seismoacoustic data. The morphology of top of the Archaean basement, the structure of the Quaternary sedimentary cover and the bottom topography were studied. A sequence of glacial deposits dating back to the last glaciation and a compound sequence of glaciolacustrine, glacial-marine and marine sediments were delineated. Spatial configuration and thickness behavior were examined. It was demonstrated that the recent bottom topography is controlled by the faults, characterized predominantly by north-western and the north-eastern strike, and affecting the entire sedimentary cover including the Holocene sediments.