Bacillus odysseyi sp. nov., a round-spore-forming bacillus isolated from the Mars Odyssey spacecraft

Abstract

A round-spore-formingBacillusspecies that produces an exosporium was isolated from the surface of the Mars Odyssey spacecraft. This novel species has been characterized on the basis of phenotypic traits, 16S rDNA sequence analysis and DNA–DNA hybridization. According to the results of these analyses, this strain belongs to the genusBacillusand is a Gram-positive, aerobic, rod-shaped, endospore-forming eubacterium. Ultrathin sections of the spores showed the presence of an exosporium, spore coat, cortex and core. 16S rDNA sequence similarities between this strain,Bacillus fusiformisandBacillus silvestriswere ∼96 % and DNA–DNA reassociation values with these two bacilli were 23 and 17 %, respectively. Spores of the novel species were resistant to desiccation, H2O2and UV and gamma radiation. Of all strains tested, the spores of this strain were the most consistently resistant and survived all of the challenges posed, i.e. exposure to conditions of desiccation (100 % survival), H2O2(26 % survival), UV radiation (10 % survival at 660 J m−2) and gamma radiation (0·4 % survival). The name proposed for this novel bacterium isBacillus odysseyisp. nov.; the type strain is 34hs-1T(=ATCC PTA-4993T=NRRL B-30641T=NBRC 100172T).