Strains ofThe genus Deinococcus includes the species Deinococcus radiodurans, Deinococcus proteolyticus, Deinococcus radiophilus, and Deinococcus radiopugnans. The species Deinococcus erythromyxa was also included in this genus as a species incertae sedis by Brooks and Murray (3). The rod-shaped organisms of the species Deinococcus grandis are very closely related to the species of the genus Deinococcus, but were classified in the genus Deinococcus primarily on the basis of morphology (36). Recently, the type strains of these species were subjected to a complete 16s ribosomal DNA (rDNA) sequence analysis, which resulted in the reclassification of Deinococcus grandis and Deinococcus erythromyxa (41). The species Deinococcus grandis, despite its rod-shaped morphology, falls within the radiation of the genus Deinococcus and for this reason was classified as Deinococcus grandis. The species Deinococcus erythromyxa was known by Brooks and Murray (3) to have characteristics that were different from those of the other species of Deinococcus, and subsequent studies confirmed its chemotaxonomic distinctiveness, which reinforced the need for reclassification of this species (12). The species Deinococcus erythromyxa has been found to be phylogenetically very closely related to the gram-positive species Kocuria rosea, but due to the low DNA-DNA hybridization values between the two species, Kocuria erythromyxa was maintained as a separate speciesThe species of the genus Deinococcus are strictly aerobic, have optimum growth temperatures in the range from 25 to 35"C, produce reddish colonies, generally stain gram positive, have ornithine in the peptidoglycan, lack teichoic acids, possess menaquinone 8 as the major respiratory quinone, and are (41).

The ionizing-radiation-resistant fractions of two soil bacterial communities were investigated by exposing an arid soil from the Sonoran Desert and a nonarid soil from a Louisiana forest to various doses of ionizing radiation using a 60 Co source. The numbers of surviving bacteria decreased as the dose of gamma radiation to which the soils were exposed increased. Bacterial isolates surviving doses of 30 kGy were recovered from the Sonoran Desert soil, while no isolates were recovered from the nonarid forest soil after exposure to doses greater than 13 kGy. The phylogenetic diversities of the surviving culturable bacteria were compared for the two soils using 16S rRNA gene sequence analysis. In addition to a bacterial population that was more resistant to higher doses of ionizing radiation, the diversity of the isolates was greater in the arid soil. The taxonomic diversity of the isolates recovered was found to decrease as the level of ionizing-radiation exposure increased. Bacterial isolates of the genera Deinococcus, Geodermatophilus, and Hymenobacter were still recovered from the arid soil after exposure to doses of 17 to 30 kGy. The recovery of large numbers of extremely ionizing-radiationresistant bacteria from an arid soil and not from a nonarid soil provides further ecological support for the hypothesis that the ionizing-radiation resistance phenotype is a consequence of the evolution of other DNA repair systems that protect cells against commonly encountered environmental stressors, such as desiccation. The diverse group of bacterial strains isolated from the arid soil sample included 60 Deinococcus strains, the characterization of which revealed nine novel species of this genus.Extreme ionizing-radiation resistance has been observed in several members of the domains Bacteria and Archaea. Of the genera containing ionizing-radiation-resistant organisms, Deinococcus and Rubrobacter show the highest levels of resistance, and all species of these genera have been shown to be

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Two isolates, belonging to a new species of a novel genus of the Phylum "Deinococcus/Thermus ", were recovered from hot spring runoffs on the Island of São Miguel in the Azores. Strains RQ-24(T) and TU-8 are the first cultured representatives of a distinct phylogenetic lineage within this phylum. These strains form orange/red colonies, spherical-shaped cells, have an optimum growth temperature of about 50 degrees C, an optimum pH for growth between about 7.5 and 9.5, and do not grow at pH below 6.5 or above pH 11.2. These organisms grow in complex media without added NaCl, but have a maximum growth rate in media with 1.0% NaCl and grow in media containing up to 6.0% NaCl. The organisms are extremely ionizing radiation resistant; 60% of the cells survive 5.0 kGy. These strains are chemoorganotrophic and aerobic; do not grow in Thermus medium under anaerobic conditions with or without nitrate as electron acceptor and glucose as a source of carbon and energy, but ferment glucose to D-lactate without formation of gas. The organisms assimilate a large variety of sugars, organic acids and amino acids. Fatty acids are predominantly iso- and anteiso-branched; long chain 1,2 diols were also found in low relative proportions; menaquinone 8 (MK-8) is the primary respiratory quinone. Peptidoglycan was not detected. Based on 16S rRNA gene sequence analysis, physiological, biochemical and chemical analysis we describe a new species of one novel genus represented by strain RQ-24(T) (CIP 108686(T)=LMG 22925(T)=DSM 17093(T)) for which we propose the name Truepera radiovictrix. We also propose the family Trueperaceae fam. nov. to accommodate this new genus.

In this study we characterized new strains of the slightly thermophilic species Rubrobacter radiotolerans and the thermophilic species Rubrobacter xylanophilus, both of which were previously represented only by the type strains isolated, respectively, from Japan and the United Kingdom. The new isolates were recovered from two hot springs in central Portugal after gamma irradiation of water and biofilm samples. We assessed biochemical characteristics, performed DNA-DNA hybridization, and carried out 16S rDNA sequence analysis to demonstrate that the new Rubrobacter isolates belong to the species R. radiotolerans and R. xylanophilus. We also show for the first time that the strains of R. xylanophilus and other strains of R. radiotolerans are extremely gamma radiation resistant.