Resistance and Raman spectroscopy analysis of Parageobacillus thermantarcticus spores after γ-ray exposure

Abstract

Spores of the genus Bacillus are able to resist ionizing radiations and therefore they are a suitable biological model for studies in Astrobiology, i.e. the multidisciplinary approach to the study of the origin and evolution of life on Earth and in the universe. The resistance to γ-radiation is an important issue in Astrobiology in relation to the search for bacterial species that could adapt to life in space. This study investigates the resistance of spores of the thermophilic bacteria Parageobacillus thermantarcticus to γ-rays. The analysis of spores' response to irradiation at a molecular level is performed by means of Raman spectroscopy that allows to get insights in the sequence of events taking place during inactivation. The role of the γ-rays' dose in the inactivation of spores is also investigated, allowing to highlight the mechanism(s) of inactivation including DNA damage, protein denaturation and calcium dipicolinate levels.

Parageobacillus thermantarcticus, an Antarctic Cell Factory: From Crop Residue Valorization by Green Chemistry to Astrobiology Studies

“…P. thermantarcticus M1 produces spores [8], and they represent a useful biological system that allows the microorganism to survive under extreme environmental conditions, including space simulation, as recently reported [12][13][14]. The genome examination highlighted several genes involved in the sporulation system, ranging from genes coding for sporulation proteins and lipoprotein, prespore-specific regulator, to spore germination proteins.…”

“…The Raman analysis showed that such spores, although still retaining their DPA content, presented a lowering in their DNA and protein integrity, as confirmed by the decrease in the relative Raman signals. In this case, the inactivation was caused by the direct interaction of γ-rays with the cellular structures and was not mediated by ROS formation [14]. Moreover, the results obtained by subjecting either the viable cells or the spores of P. thermantarcticus to space simulation are interesting for the issue of origin of life.…”

“…The investigation of bacterial spores' resistance to ionizing radiations, which represent a major part of the cosmic radiation spectrum, is one of the main issues for the study of habitability. Therefore, further studies were performed using exposure of the spores of P. thermantarcticus to irradiation with UV and γ-rays [14]. In both cases, resistance to irradiation was assessed by measuring D 10 , which represents the radiation dose required to inactivate 90% of the starting spores' population.…”

“…thermantarcticus has also been used as a biological model for astrobiology, i.e., the multidisciplinary approach to the study of origin and evolution of life on Earth and in the Universe. It has been demonstrated that either the viable cells or the spores of P. thermantarcticus to space simulation are interesting for the issue of the origin of life [12][13][14]. Indeed, the finding of bacterial species fit to survive in space parameters open new scenarios for the so-called panspermia theory.…”

Graphene-Based and Surface-Enhanced Raman Spectroscopy for Monitoring the Physio-Chemical Response of Thermophilic Bacterial Spores to Low Temperatures Exposure

“…The doping level affects the vibrational energies of the graphene that can be monitored by conventional Raman spectroscopy. Additional information on the biochemical changes can also be obtained by means of Raman spectroscopy [14][15][16][17] or Surface-Enhanced Raman Spectroscopy (SERS) [18,19]. In particular, a great interest is devoted to SERS due to its high sensitivity and selectivity [20].…”