Freshwater ostracodes in Quaternary permafrost deposits from the Siberian Arctic

Ostracode analysis was carried out on samples from ice-rich permafrost deposits obtained on the BykovskyPeninsula (Laptev Sea).A composite pro file was investigated that covers most of a 38-m thick permafrostsequence and corresponds to the last ca.60 kyr of the Late Quaternary.The ostracode assemblages aresimilar to those known from European Quaternary lake deposits during cold stages.The ostracode habitatswere small,shallow,cold,oligotrophic pools located in low centred ice wedge polygons or in small ther-mokarst depressions.In total,15 taxa,representing 7 genera,were identi fied from 65 samples.The studiedsection is subdivided into six ostracode zones that correspond to Late Quaternary climatic and environ-mental stadial-interstadial variations established by other paleoenvironmental proxies:(1)cold and dryZyrianian stadial (58 53 kyr BP);(2)warm and dry Karginian interstadial (48 34 kyr BP);(3)transitionfrom the Karginian interstadial to the cold and dry Sartanian stadial (34 21 kyr BP);(4)transition fromthe Sartanian stadial to the warm and dry Late Pleistocene period,the Allerød (21 14 kyr BP);(5)transition from the Allerød to the warm and wet Middle Holocene (14 7 kyr BP);and (6)cool and wetLate Holocene (ca.3 kyr BP).The abundance and diversity of the ostracodes will be used as an additionalbioindicator for paleoenvironmental reconstructions of the Siberian Arctic

Methylotetracoccus oryzae strain C50C1 is a novel type Ib gammaproteobacterial methanotroph adapted to freshwater environments

Methane-oxidizing microorganisms perform an important role in reducing emissions of the greenhouse gas methane to the atmosphere. To date, known bacterial methanotrophs belong to the Proteobacteria, Verrucomicrobia, and NC10 phyla. Within the Proteobacteria phylum, they can be divided into type Ia, type Ib, and type II methanotrophs. Type Ia and type II are well represented by isolates. Contrastingly, the vast majority of type Ib methanotrophs have not been able to be cultivated so far. Here, we compared the distributions of type Ib lineages in different environments. Whereas the cultivated type Ib methanotrophs (Methylococcus and Methylocaldum) are found in landfill and upland soils, lineages that are not represented by isolates are mostly dominant in freshwater environments, such as paddy fields and lake sediments. Thus, we observed a clear niche differentiation within type Ib methanotrophs. Our subsequent isolation attempts resulted in obtaining a pure culture of a novel type Ib methanotroph, tentatively named "Methylotetracoccus oryzae" C50C1. Strain C50C1 was further characterized to be an obligate methanotroph, containing C16:1ω9c as the major membrane phospholipid fatty acid, which has not been found in other methanotrophs. Genome analysis of strain C50C1 showed the presence of two pmoCAB operon copies and XoxF5-type methanol dehydrogenase in addition to MxaFI. The genome also contained genes involved in nitrogen and sulfur cycling, but it remains to be demonstrated if and how these help this type Ib methanotroph to adapt to fluctuating environmental conditions in freshwater ecosystems.BT/Environmental Biotechnolog