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.