Project description:A Gram-stain-negative, nonspore-forming, nonmotile, aerobic, rod-shaped, and very pale orange-colored bacterial strain, designated TS293T, was isolated from a sand sample obtained from a coastal dune after exposure to 3kGy of gamma (γ)-radiation. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the isolate was a member of the genus Deinococcus and clustered with D. deserti VCD115T. The genome of strain TS293T was 4.62 Mbp long (68.2% G + C content and 4124 predicted genes) divided into a 2.86Mb main chromosome and five plasmids. Many genes considered to be important to the γ-radiation and oxidative stress resistance of Deinococcus were conserved in TS293T, but genome features that could differentiate TS293T from D. deserti and D. radiodurans, the type species of the Deinococcus genus, were also detected. Strain TS293T showed resistance to γ-radiation with D10 values (i.e., the dose required to reduce the bacterial population by tenfold) of 3.1kGy. The predominant fatty acids of strain TS293T were summed feature 3 (C16:1 ω6c and/or C16:1 ω7c) and iso-C16:0. The major polar lipids were two unidentified phosphoglycolipids and one unidentified glycolipid. The main respiratory quinone was menaquinone-8. Based on the phylogenetic, genomic, physiological, and chemotaxonomic characteristics, strain TS293T represents a novel species, for which the name Deinococcus taeanensis sp. nov. is proposed. The type strain is TS293T (= KCTC 43191T = JCM 34027T).
Project description:The extreme radiation resistance of Deinococcus bacteria requires the radiation-stimulated cleavage of protein DdrO by a specific metalloprotease called IrrE. DdrO is the repressor of a predicted radiation/desiccation response (RDR) regulon, composed of radiation-induced genes having a conserved DNA motif (RDRM) in their promoter regions. Here, we showed that addition of zinc ions to purified apo-IrrE, and short exposure of Deinococcus cells to zinc ions, resulted in cleavage of DdrO in vitro and in vivo, respectively. Binding of IrrE to RDRM-containing DNA or interaction of IrrE with DNA-bound DdrO was not observed. The data are in line with IrrE being a zinc peptidase, and indicate that increased zinc availability, caused by oxidative stress, triggers the in vivo cleavage of DdrO unbound to DNA. Transcriptomics and proteomics of Deinococcus deserti confirmed the IrrE-dependent regulation of predicted RDR regulon genes and also revealed additional members of this regulon. Comparative analysis showed that the RDR regulon is largely well conserved in Deinococcus species, but also showed diversity in the regulon composition. Notably, several RDR genes with an important role in radiation resistance in Deinococcus radiodurans, for example pprA, are not conserved in some other radiation-resistant Deinococcus species.