Antarcticibacterium arcticum sp. nov., a bacterium isolated from marine sediment of the Canadian Beaufort Sea

A Gram-stain-negative, aerobic, yellow-pigmented, flexirubin-negative, rod-shaped and non-motile bacterial strain, PAMC 28998T, was isolated from a surface sediment sample collected from the Canadian Beaufort Sea. Strain PAMC 28998T grew at 4–37 °C (optimum, 25 °C), at pH 7.0–9.0 (optimum, pH 7.5) and in the presence of 1.0–10.0 % (w/v) NaCl. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain PAMC 28998T belongs to the genus Antarcticibacterium showing the highest sequence similarity (96.8 %) with Antarcticibacterium flavum JB01H24T. The average nucleotide identity and genome-to-genome distance values between PAMC 28998T and the most closely related species ( A. flavum JB01H24T) were 74.1 and 18.5 %, respectively, indicating that strain PAMC 28998T is clearly distinguished from A. flavum . The genomic DNA G+C content calculated from genome sequences was 39.8 %. The major fatty acids (>10 %) were iso-C15 : 0 (19.5 %), anteiso-C15 : 0 (18.0 %), iso-C16 : 0 (11.6 %) and summed feature 3 (C16:1 ω6c and/or C16:1 ω7c; 11.4 %). The major polar lipids were phosphatidylethanolamine, aminoglycolipid, two unidentified aminolipids, three unidentified phospholipids and four unidentified lipids. The major respiratory quinone was MK-6. Based on the phylogenetic, genomic and phenotypic data presented here, strain PAMC 28998T is considered to represent a novel species of the genus Antarcticibacterium , for which the name Antarcticibacterium arcticum sp. nov. is proposed with the strain PAMC 28998T (=KCCM 43316 T=JCM 33514T).

Seasonality of chrysophyte cyst and diatom assemblages in varved Lake Nautajärvi – implications for palaeolimnological studies

Phytoplankton species composition is strongly affected by seasons, which should be taken into account in palaeolimnological studies. Although chrysophyte cysts and diatoms are widely used as palaeobioindicators in palaeolimnological studies, only recently have attempts been made to use their modern deposition from sediment trap data to provide more detailed, seasonal-based environmental reconstructions. In this study sediment traps were used to record seasonality of chrysophyte cysts and diatoms during two climatically different years 2009 and 2010 in an annually laminated Lake Nautajärvi, Finland, and this seasonal data was then compared with the fossil record derived from the surface sediment of the lake. The overall changes in cyst and diatom assemblages between years and seasons are subtle. For both groups, no clear connection to any particular season could be detected in the sediment surface. Despite the climatological differences between the study years, the inter-annual accumulation rates of both algal groups were surprisingly similar, whereas the intra-annual accumulation rates differed substantially. This and the high amount of taxa occurring during all seasons in the trap samples implies that primary producers are more dependent on prevailing seasonal limnological conditions than on rapid, shortly lived episodes. Redundancy analysis (RDA) revealed that chrysophyte cyst assemblages from the spring sediment trap are mainly controlled by the spring discharge intensity, a surrogate variable of spring weather conditions, whereas precipitation and air temperature have the strongest impact on the summer assemblages. However, only discharge explains statistically significantly the variance in the cyst data. Precipitation and air temperature have the strongest impact on the diatom summer samples, whereas the spring sediment trap sample of the snowy and harsh winter of 2010 was strongly correlated with the spring discharge. However, none of the measured environmental variables explains the variance in the diatom data statistically significantly. The similarity between the algae found in the sediment traps and surface sediment sample suggests that within small and shallow lakes without any extreme environmental settings the surface sediment sample represents well the lake´s overall algal composition and can thus be used in palaeolimnological studies.