ULTRAVIOLET RADIATIONS RESISTANCE OF SPORES FROM TWO NOVEL BACILLUS HORNECKIAE STRAINS OF SHALLOW MARINE HYDROTHERMAL ORIGIN

Spores from Bacillus are able to survive to different environmental stressors, including the ultraviolet radiations (UVR) exposition. Bacillus horneckiae is a novel radioresistant,extremophile isolated from a Phoenix spacecraft assembly clean room able to resist to UVR. The aims of the present study were: i) to evaluate the UVR resistance of spores from two novel thermotolerant Bacillus horneckiae strains (APA and SBP3), isolated from shallow marine vents of Panarea Island (Italy); and ii) to explore the external catalase activity, as putative resistance mechanism against UVR exposition. After purification from vegetative cells, spores were exposed to UVA (λ=365nm) and UVC (λ=253nm). Catalase activity was spectrophotometrically determined by measuring the decomposition of H2O2 (0.05% v/v). The spores from both strains showed UVA resistance to 80 J/m2. Spores from strain SBP3 were more resistant to UVC (up to 480 J/m2) than those from strain APA (240 J/m2). After UVA exposition (10 min), spores from both strains, surviving to H2O2 treatment, possessed a major catalase activity (34% from APA and 38% from SBP3) than unexposed spores. These results suggest that in addition to the coat structure, catalase could play an important role in spores-UVR resistance, inactivating the damage of reactive oxygen species, derived by radiations on vital biomolecules (proteins and nucleic acids). Radioprotective core component and the external catalase of the novel bacilli represent new models to investigating the responses to environmental oxidative stressors. Catalase from these bacilli could provide useful applications for industrial (cosmeceutical, food, pharmaceutical) as well as environmental and biotechnological purposes.