Ionizing-radiation-resistant Kocuria rhizophila PT10 isolated from the Tunisian Sahara xerophyte Panicum turgidum: Polyphasic characterization and proteogenomic arsenal.

A new strain belonging to the genus Kocuria, designed PT10, was isolated from irradiated roots of the xerophyte Panicum turgidum. Isolate PT10 is a Gram-positive, coccoid, aerobic and ionizing-radiation (IR)-resistant actinobacterium. PT10 has shown an ability to survive under extreme conditions, such as gamma irradiation, desiccation and high concentration of hydrogen peroxide. Phenotypic, chemotaxonomic and comparative genome analyses support the assignment of strain PT10 (LMG 31102 = DSM 108617) as Kocuria rhizophila. The complete genome sequence of PT10 consists of one chromosome (2,656,287 bps), with a 70.7% G + C content and comprises 2481 protein-coding sequences. A total of 1487 proteins were identified by LC-MS/MS profiling. In silico analyses revealed that the proteome of the oxidation-tolerant PT10 possesses several features explaining its IR-resistant phenotype and many adaptive pathways implicated in response to environmental pressures - desiccation, cold, reactive oxygen species and other stressors.

Guesmi S ，Pujic P ，Nouioui I ，Dubost A ，Najjari A ，Ghedira K ，Igual JM ，Miotello G ，Cherif A ，Armengaud J ，Klenk HP ，Normand P ，Sghaier H ... -  《-》

Draft genome sequence of Promicromonospora panici sp. nov., a novel ionizing-radiation-resistant actinobacterium isolated from roots of the desert plant Panicum turgidum.

Guesmi S ，Nouioui I ，Pujic P ，Dubost A ，Najjari A ，Ghedira K ，Igual JM ，Cherif A ，Klenk HP ，Sghaier H ，Normand P ... -  《-》

Roots of the xerophyte Panicum turgidum host a cohort of ionizing-radiation-resistant biotechnologically-valuable bacteria.

Bacterial communities associated with roots of Panicum turgidum, exposed to arid conditions, were investigated with a combination of cultural and metataxonomic approaches. Traditional culture-based techniques were used and 32 isolates from the irradiated roots were identified as belonging to Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria phyla. Four actinobacterial strains were shown to be ionizing-radiation (IR)-resistant: Microbacterium sp. PT8 (4.8 kGy (kGy)), Micrococcus sp. PT11 (4.4 kGy), Kocuria rhizophila PT10 (2.9 kGy) and Promicromonospora panici PT9T (2.6 kGy), based on the D10 dose necessary for a 90% reduction in colony forming units (CFU). Concerning the investigation of microbial communities in situ, metataxonomic analyses of the diversity of IR-resistant microorganisms associated with irradiated roots revealed a marked dominance of Actinobacteria (46.6%) and Proteobacteria (31.5%) compared to Bacteroidetes (4.6%) and Firmicutes (3.2%). Gamma irradiation not only changed the structure of bacterial communities, but also affected their functional properties. Comparative analyses of metabolic profiles indicated the induction of several pathways related to adaptation to oxidative stress in irradiated roots, such as DNA repair, secondary metabolites synthesis, reactive oxygen species (ROS)-mitigating enzymes, etc. P. turgidum is emblematic of desert-adapted plants. Until now, there is no other work that has focused on the microbial profile of irradiated roots of this xerophyte.

Guesmi S ，Najjari A ，Pujic P ，Ghedira K ，Ouertani R ，Jabberi M ，Cherif A ，Normand P ，Sghaier H ... -  《-》

Effect of gamma irradiation on the proteogenome of cold-acclimated Kocuria rhizophila PT10.

The effects of ionizing radiation (IR) on the protein dynamics of cold-stressed cells of a radioresistant actinobacterium, Kocuria rhizophila PT10, isolated from the rhizosphere of the desert plant Panicum turgidum were investigated using a shotgun methodology based on nanoflow liquid chromatography coupled to tandem mass spectrometry. Overall, 1487 proteins were certified, and their abundances were compared between the irradiated condition and control. IR of cold-acclimated PT10 triggered the over-abundance of proteins involved in (1) a strong transcriptional regulation, (2) amidation of peptidoglycan and preservation of cell envelope integrity, (3) detoxification of reactive electrophiles and regulation of the redox status of proteins, (4) base excision repair and prevention of mutagenesis and (5) the tricarboxylic acid (TCA) cycle and production of fatty acids. Also, one of the more significant findings to emerge from this study is the SOS response of stressed PT10. Moreover, a comparison of top hits radio-modulated proteins of cold-acclimated PT10 with proteomics data from gamma-irradiated Deinococcus deserti showed that stressed PT10 has a specific response characterised by a high over-abundance of NemA, GatD, and UdgB.

Guesmi S ，Ghedira K ，Pujic P ，Najjari A ，Miotello G ，Cherif A ，Narumi I ，Armengaud J ，Normand P ，Sghaier H ... -  《-》

Isolation a new strain of Kocuria rosea capable of tolerating extreme conditions.

A new actinobacterial strain was isolated from Ab-e-Siah spring (dark water) taken from the Ramsar city in Iran, and subjected to several stress conditions investigation. The isolate, named MG2 strain, was Gram-positive, aerobic, diplococci or tetrad shaped, non-spore forming and non-motile. Phylogenetic analysis of the isolate using 16S rDNA sequence indicated that the organism matched best with the genus Kocuria and the highest sequence similarities (98.55%) being found with Kocuria rosea. The 16S rDNA sequence determined in this study has been deposited in the NCBI database with the accession no. JX534199, K. rosea strain MG2. The isolated strain was an alkaliphilic-mesophilic bacterium because the optimal growth was observed at pH 9.2 and temperature of 28 °C under aerobic condition. MG2 was a halotolerant strain and tolerated maximally to 15% NaCl concentraion. Viability analysis by flow cytometry indicated that this strain had highly resistance to UV-C radiation and moderately resistance to desiccation after 28 days. The viability of K. rosea strains MG2 and Deinococcus radiodurans R1 were determined D87 and D98 according to D index, respectively, by a dose radiation 25 J/cm (Appukuttan et al., 2006). Thus the UV resistance of strain MG2 was comparable with representative radiation resistant Deinococcus. Also MG2 was grown at 1-4% of H2O2 as an oxidant agent. This research is the first study on multiple extreme resistance of Kocuria rosea new strain (MG2) isolated in Iran.

Gholami M ，Etemadifar Z ，Bouzari M 《-》