Novel sialidase from non-pathogenic bacterium Oerskovia paurometabola strain O129.

Bacterial sialidases are enzymes that are involved in a number of vital processes in microorganisms and in their interaction with the host or the environment. Their wide application for scientific and applied purposes requires the search for highly effective and non-pathogenic producers. Here, we report the first description of sialidase from Oerskovia paurometabola. The extracellular enzyme preparation was partially purified. The presence of sialidase was confirmed in native PAGE treated with the fluorogenic substrate 4MU-Neu5Ac. Maximum enzyme activity was registered at 37 °C and in the pH range of 4.0-5.5. The influence of metal ions and EDTA was examined. It was demonstrated that EDTA, Mn2+ and Ba2+ ions inhibit the sialidase activity to different extent, while Cd2+, Fe2+ and Fe3+ have stimulating effect on it. These features are studied for the first time concerning sialidase of Oerskovia representative. Cell bound sialidase and sialate aldolase were also established.

Temperature downshift induces antioxidant response in fungi isolated from Antarctica.

Although investigators have been studying the cold-shock response in a variety of organisms for the last two decades or more, comparatively little is known about the difference between antioxidant cell response to cold stress in Antarctic and temperate microorganisms. The change of environmental temperature, which is one of the most common stresses, could be crucial for their use in the biotechnological industry and in ecological research. We compared the effect of short-term temperature downshift on antioxidant cell response in Antarctic and temperate fungi belonging to the genus Penicillium. Our study showed that downshift from an optimal temperature to 15 degrees or 6 degrees C led to a cell response typical of oxidative stress: significant reduction of biomass production; increase in the levels of oxidative damaged proteins and accumulation of storage carbohydrates (glycogen and trehalose) in comparison to growth at optimal temperature. Cell response against cold stress includes also increase in the activities of SOD and CAT, which are key enzymes for directly scavenging reactive oxygen species. This response is more species-dependent than dependent on the degree of cold-shock. Antarctic psychrotolerant strain Penicillium olsonii p14 that is adapted to life in extremely cold conditions demonstrated enhanced tolerance to temperature downshift in comparison with both mesophilic strains (Antarctic Penicillium waksmanii m12 and temperate Penicillium sp. t35).

Cell response of Antarctic and temperate strains of Penicillium spp. to different growth temperature.

The effect of growth temperature (10, 15, 20, 25, and 30 degrees C) on the cell response was compared between two Antarctic Penicillium sp. strains (Penicillium sp. p14 and Penicillium sp. m12) and a European temperate strain, Penicillium sp. t35. According to the temperature profiles, Penicillium sp. p14 was identified as psychrophilic, while Penicillium sp. m12 and Penicillium sp. t35 as mesophilic fungi, respectively. The results demonstrated that the growth at low temperature does clearly induce oxidative stress events in all strains tested. Decreases in growth temperature below the optimal coincided with markedly enhanced protein carbonyl content, an indicator of oxidatively damaged proteins. Also, the cellular response to growth temperature in terms of reserve carbohydrate was determined. In the mesophilic strains there was essentially no enhancement of glycogen content. This was in contrast to the psychrophilic Penicillium sp. p14, which gradually accumulated glycogen in response to cold (10 degrees C) during the exponential phase. In addition, elevated endogenous levels of trehalose upon low-temperature stress were exhibited by all model microorganisms. Compared with temperate mesophilic Penicillium sp. t35, Antarctic strains (psychrophilic Penicillium sp. p14 and mesophilic Penicillium sp. m12) demonstrated a marked rise in activities of protective enzymes such as superoxide dismutase and catalase at decreasing temperatures. The results suggested that low-temperature resistance is partially associated with enhanced scavenging systems.