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Five psychrophilic bacterial strains were isolated from soil samples collected above the treeline of alpine environments. Phylogenetic analysis based on 16S rRNA gene sequences indicated that these organisms represent four novel species of the genus Deinococcus; levels of sequence similarity to the type strains of recognized Deinococcus species were in the range 89.3-94.7%. Strains PO-04-20-132(T), PO-04-20-144, PO-04-19-125(T), ME-04-01-32(T) and ME-04-04-52(T) grew aerobically, with optimum growth at 10 degrees C and at pH 6-9. The major respiratory menaquinone was MK-8. The fatty acid profiles of strains PO-04-20-132(T), PO-04-20-144, PO-04-19-125(T) and ME-04-01-32(T) were dominated by 16:1 omega 7c, 17:0 iso and 15:1 omega 6c, whereas 16:1 omega 7c, 17:0 cyclo and 16:0 predominated in strain ME-04-04-52(T). The DNA G + C contents of strains PO-04-20-132(T), PO-04-19-125(T), ME-04-01-32(T) and ME-04-04-52(T) were 63.2, 63.1, 65.9 and 62.6 mol%, respectively. Strains PO-04-20-132(T), PO-04-19-125(T), ME-04-01-32(T) and ME-04-04-52(T) had gamma radiation D-10 (dose required to reduce the bacterial population by 10-fold) values of <= 4 kGy. These four strains showed sensitivity to UV radiation and extended desiccation as compared with Deinococcus radiodurans. On the basis of the phylogenetic analyses, and chemotaxonomic and phenotypic data, it is proposed that strains PO-04-20-132(T) (=LMG 24019(T) =NRRL B-41950(T) Deinococcus radiomollis sp. nov.), PO-04-19-125(T) (=LMG 24282(T) =NRRL B-41949(T) Deinococcus claudionis sp. nov.), ME-04-01-32(T) (=LMG 24022(T) =NRRL B-41947(T) Deinococcus altitudinis sp. nov.) and ME-04-04-52(T) (=LMG 24283(T) =NRRL B-41948(T) Deinococcus alpinitundrae sp. nov.) represent the type strains of four novel species of the genus Deinococcus.