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The diversity of culturable filamentous microfungi in peat and sediments of four peatlands at the coastal zone of Kandalaksha Bay of the White Sea (Murmansk region, Russia) was studied by culture methods on standard and selective media. Annually 100 samples were collected from the bogs 2007-2010. Based on morphological, molecular markers and cultural features, 211 taxa were identified. Fungal communities observed at the peatlands were influenced mostly by their sea origin. We discovered a large difference between fungal communities from the peat and the sediments of the peatlands. In contrast to the sediments, the fungal community of the peat was found to be consistent throughout sampling sites. Fungi with specific ecophysiology, such as Sphagnum-decomposing species (Oidiodendron griseum, O. tenuissimum. Penicillium spinulosum, P. thomii, Talaromyces funiculosus), psychrotolerant and associated with insects species (Pseudogymnoascus pannorum, Tolypocladium spp.), typical marine species (Acremonium spp.) were found. In addition, different types of sterile mycelia were characteristic for the researched peatlands.

Acidophiles maintain near-neutral intracellular pH using proton pumps. We have suggested the protective role of osmolytes and membrane lipids in the adaptation to an acidic environment. Previously we have observed, for the first time, high levels of trehalose in acidophilic basidiomycete Sistotrema brinkmannii. Here, we have studied the composition of both osmolytes and membrane lipids of two more acidophilic fungi. Trehalose and polyols were among the main osmolytes during growth under optimal conditions (pH 4.0) in basidiomycete Phlebiopsis gigantea and ascomycete Mollisia sp. Phosphatidic acids, phosphatidylethanolamines, phosphatidylcholines, and sterols, were predominant membrane lipids in both fungi. P. gigantea had a narrow optimum of growth at pH 4.0, resulting in a sharp decline of growth rate at pH 2.6 and 5.0, accompanied by a decrease in the number of osmolytes and significant changes in the composition of membrane lipids. In contrast, Mollisia sp. had a broad optimal growth range (pH 3.0–5.0), and the number of osmolytes either stayed the same (at pH 6.0) or increased (at pH 2.6), while membrane lipids composition remained unchanged. Thus, the data obtained indicate the participation of osmolytes and membrane lipids in the adaptation of acidophilic fungi.

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