Deinococcus deserti sp. nov., a gamma-radiation-tolerant bacterium isolated from the Sahara Desert

Abstract

Two gamma-and UV-radiation-tolerant, Gram-negative, rod-shaped bacterial strains, VCD115 T and VCD117, were isolated from a mixture of sand samples collected in the Sahara Desert in Morocco and Tunisia, after exposure of the sand to 15 kGy gamma radiation. Phylogenetic analysis based on 16S rRNA gene sequences and DNA-DNA hybridizations showed that VCD115 T and VCD117 are members of a novel species belonging to the genus Deinococcus, with Deinococcus grandis as its closest relative. The DNA G+C contents of VCD115 T and VCD117 are 59?8 and 60?6 mol%, respectively. The major fatty acids (straight-chain 15 : 1, 16 : 1, 17 : 1 and 16 : 0), polar lipids (dominated by phosphoglycolipids and glycolipids) and quinone type support the affiliation to the genus Deinococcus. The strains did not grow on rich medium such as trypticase soy broth (TSB), but did grow as whitish colonies on tenfold-diluted TSB. The genotypic and phenotypic properties allowed differentiation of VCD115 T and VCD117 from recognized Deinococcus species. Strains VCD115 T and VCD117 are therefore identified as representing a novel species, for which the name Deinococcus deserti sp. nov. is proposed, with the type strain VCD115 T (=DSM 17065 T =LMG 22923 T ).Various bacterial species have the capacity to survive under conditions that are commonly considered as extreme, for example in environments experiencing high pressure or high salt concentrations. In our laboratory, we are studying bacteria that live in the upper sand layers of deserts, where they are exposed to cycles of high and low temperatures, and to cycles of desiccation and hydration. De-and rehydration may cause DNA damage in these bacteria, and in order to survive they probably possess efficient DNA-repair mechanisms. Ionizing radiation causes similar types of DNA damage including double-strand breaks, which are the most deleterious to the organism (Mattimore & Battista, 1996). Bacteria belonging to the genus Deinococcus, in particular the well-studied Deinococcus radiodurans, have the distinctive feature of being the most radiation-tolerant of vegetative cells. D. radiodurans can withstand doses of radiation a thousand times higher than a human can. It can survive doses of radiation that do not exist naturally on Earth. Therefore, it is likely that this radiation tolerance is related to the bacterial response to natural non-radioactive DNA-damaging conditions such as desiccation (Makarova et al., 2001). At the time of writing, eight recognized species belong to the genus Deinococcus (Ferreira et al., 1997;Rainey et al., 1997;Suresh et al., 2004). Three other species have been described very recently, 'Deinococcus frigens', 'Deinococcus saxicola' and 'Deinococcus marmoris ' (Hirsch et al., 2004). Only D. radiodurans R 1 T has been studied extensively. Its genome has been sequenced (White et al., 1999), and analyses of the transcriptome (Liu et al., 2003;Tanaka et al., 2004) . For all other tests, bacterial strains were cultivated at 30 u C in TSB/10 or on agar plates containing the same m...

Radiation resistant of native Deinococcus spp. isolated from the Lout desert of Iran “the hottest place on Earth”

“…Many Deinococcus species has been isolated from deserts and arid places such as D. deserti that were isolated from the Sahara desert in Morocco (de Groot et al 2005), D. xinjiangensis isolated from Taklimakan desert of Xinjiang, China (Peng et al 2009), D. gobiensis isolated from Gobi desert, Xinjiang, China (Yuan et al 2009), D. peraridilitoris isolated from a coastal desert in Chile (Rainey et al 2007) (Rainey et al 2005). These bacteria possess efficient DNA repair mechanisms and so can survive (de Groot et al 2005).…”

“…These bacteria possess efficient DNA repair mechanisms and so can survive (de Groot et al 2005). Many of DNA damages such as double-strand breaks (DSBs) are caused by ionizing radiation which is the most lethal factor for organisms (Mattimore and Battista 1996).…”

“…Hymenobacter sp. and others that are able to tolerate radiation without forming spores (de Groot et al 2005;Kim et al 2008). A few numbers of strains isolated from non-irradiated samples demonstrate that the extreme radiation resistance of the organisms is not a result of selection of resistant strains by irradiation.…”

“…D. radiodurans can withstand doses of radiation a thousand times higher than a human can. It survives under doses of radiation that do not exist naturally on earth (de Groot et al 2005). It seems that this radiation resistance is related to the bacterial response to natural non-radioactive DNA-damaging conditions such as desiccation (Makarova et al 2001).…”

Mutagenic lesion bypass and two functionally different RecA proteins in Deinococcus deserti

“…Recently, the genome of Deinococcus deserti, a bacterium isolated from surface sand of the Sahara desert (de Groot et al, 2005), was sequenced and analysed (de Groot et al, 2009). Its genome consists of a 2.8 Mb chromosome and three large plasmids of 324, 314 and 396 kb.…”