Masaharu Tsuji

Comparative analysis of milk fat decomposition activity by Mrakia spp. isolated from Skarvsnes ice-free area, East Antarctica.

Milk fat curdle is difficult to remove from sewage. In an attempt to identify an appropriate agent for bio-remediation of milk fat curdle, Mrakia strains were collected from the Skarvsnes ice-free area of Antarctica. A total of 27 strains were isolated and tested for their ability to decompose milk fat at temperatures ranging from 4°C to 15°C. All strains could decompose milk fat at 4°C and 10°C. Phylogenetic analysis and comparison of the decomposition ability of milk fat (DAMF) revealed that the DAMF may be useful for predicting the outcome of phylogenetic analysis based on ITS sequences.

Cold-stress responses in the Antarctic basidiomycetous yeast Mrakia blollopis.

Microbes growing at subzero temperatures encounter numerous growth constraints. However, fungi that inhabit cold environments can grow and decompose organic compounds under subzero temperatures. Thus, understanding the cold-adaptation strategies of fungi under extreme environments is critical for elucidating polar-region ecosystems. Here, I report that two strains of the Antarctic basidiomycetous yeast Mrakia blollopis exhibited distinct growth characteristics under subzero conditions: SK-4 grew efficiently, whereas TKG1-2 did not. I analysed the metabolite responses elicited by cold stress in these two M. blollopis strains by using capillary electrophoresis–time-of-flight mass spectrometry. M. blollopis SK-4, which grew well under subzero temperatures, accumulated high levels of TCA-cycle metabolites, lactic acid, aromatic amino acids and polyamines in response to cold shock. Polyamines are recognized to function in cell-growth and developmental processes, and aromatic amino acids are also known to improve cell growth at low temperatures. By contrast, in TKG1-2, which did not grow efficiently, cold stress strongly induced the metabolites of the TCA cycle, but other metabolites were not highly accumulated in the cell. Thus, these differences in metabolite responses could contribute to the distinct abilities of SK-4 and TKG1-2 cells to grow under subzero temperature conditions.

Characterisation of yeast and filamentous fungi from Brøggerbreen glaciers, Svalbard

Cryoconite holes have ecological and biotechnological importance. This article presents results on culturable cryophilic yeasts and filamentous fungi isolated from cryoconite holes at Austre and Vestre Brøggerbreen glaciers, Svalbard. Based on DNA sequence data, these were identified as Rhodotorula sp., Thelebolus sp., and Articulospora tetracladia. Amongst these, Articulospora tetracladia (88.7–89.4% gene similarity with 5.8S rDNA) is a novel species, yet to be described. Filamentous fungus Articulospora sp. Cry-FB1 and Cry-FB2, expressed high amylase, cellulase, lipase and protease activities while yeast Rhodotorula sp. Cry-FB3 showed high amylase and cellulase activity. Thelebolus sp. Cry-YB 240 and Cry-YB 241 showed protease and urease activities. The effects of temperature, and salt on the growth of the cultures were studied. Optimum temperature of growth was on 10oC at pH 7.0. Filamentous fungi and yeast in the cryoconite holes possibly drive the process of organic macromolecule degradation through cold-adapted enzyme secretion, thereby assisting in nutrient cycling in these supraglacial environments. Further, these cryophilic fungi, due to their enzyme producing ability, may provide an opportunity for biotechnological research in the Arctic.