MoaE Is Involved in Response to Oxidative Stress in Deinococcus radiodurans

Surviving the storm: exploring the role of natural transformation in nutrition and DNA repair of stressed Deinococcus radiodurans

Deinococcus radiodurans, a natural transformation (NT)-enabled bacterium renowned for its exceptional radiation resistance, employs unique DNA repair and oxidative stress mitigation mechanisms as a strategic response to DNA damage. This study excavates into the intricate roles of NT machinery in the stressed D. radiodurans, focusing on the genes comEA, comEC, endA, pilT, and dprA, which are instrumental in the uptake and processing of extracellular DNA (eDNA). Our data reveal that NT not only supports the nutritional needs of D. radiodurans under stress but also has roles in DNA repair. The study findings establish that NT-specific proteins (ComEA, ComEC, and endonuclease A [EndA]) may contribute to support the nutritional requirements in unstressed and heavily DNA-damaged cells, while DprA contributes differently and in a context-dependent manner to navigating through the DNA damage storm. Thus, this dual functionality of NT-specific genes is proposed to be a contributing factor in the remarkable ability of D. radiodurans to survive and thrive in environments characterized by high levels of DNA-damaging agents.IMPORTANCEDeinococcus radiodurans is a bacterium known for its extraordinary radiation resistance. This study explores the roles of NT machinery in the radiation-resistant bacterium Deinococcus radiodurans, focusing on the genes comEA, comEC, endA, pilT, and dprA. These genes are crucial for the uptake and processing of eDNA and contribute to the bacterium nutritional needs and DNA repair under stress. The findings suggest that the NT-specific proteins ComEA, ComEC, and EndA may help meet the nutritional needs of unstressed and heavily DNA-damaged cells, whereas DprA plays a distinct role that varies, depending on the context in aiding cells to cope with DNA damage. The functionality of NT genes is proposed to enhance D. radiodurans survival in environments with high levels of DNA-damaging agents.

The Predatory Properties of Bradymonabacteria, the Representative of Facultative Prey-Dependent Predators

Bradymonabacteria, as the representative of the facultative prey-dependent predators, were re-classified from the preceding Deltaproteobacteria into the phylum Myxococcota and proposed as a novel class named Bradymonadia. However, it was ambiguous whether their predatory pattern and properties were similar to those of the other myxobacterial predators. Therefore, the physiologic features were compared to determine the similarities and differences during the process of group attack and kin discrimination. Comparative genomic analyses were performed to conclude the core genome encoded commonly by bradymonabacteria, Myxococcia, and Polyangia. In conclusion, we proposed that bradymonabacteria have a predation pattern similar to the that of the representative of opportunistic predators like Myxococcus xanthus but with some subtle differences. Their predation was predicted to be initiated by the needle-less T3SS*, and the S-motility mediated by T4P also participated in the process. Meanwhile, their group attacks relied on cell contact and cell destiny. Inter-species (strains) kin discriminations occurred without the existence of T6SS. However, no extracellular lethal substance was detected in the fermentation liquor culture of bradymonabacteria, and the death of prey cells could only be observed when touched by their cells. Moreover, the prey-selective predation was observed when the predator encountered certain prey from Bacillus (G+), Algoriphagus (G-), and Nocardioides (G+). Bradymonabacteria can be regarded as a potential consumer and decomposer, and preying on many sea-dwelling or human pathogenic bacteria allows this group a broad application prospect in marine culture and clinical disease control. Our study will provide more evidence for its exploitations and applications.

Deinococcus arenicola sp. nov., a novel radiation-resistant bacterium isolated from sandy soil in Antarctica

A Gram-stain-positive, aerobic, non-mobile and spherical strain, designated ZS9-10T, belonging to the genus Deinococcus was isolated from soil sampled at the Chinese Zhong Shan Station, Antarctica. Growth was observed in the presence of 0-4 % (w/v) NaCl, at pH 7.0-8.0 and at 4-25 °C. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain ZS9-10T formed a lineage in the genus Deinococcus. It exhibited highest sequence similarity (97.4 %) to Deinococcus marmoris DSM 12784T. The major phospholipids of ZS9-10T were unidentified phosphoglycolipid, unidentified glycolipids and unidentified lipids. The major fatty acids were summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c), C16 : 0 and C16 : 1  ω7c. MK-8 was the predominant respiratory quinone. The digital DNA-DNA hybridization and average nucleotide identity values between strain ZS9-10T and its close relative D. marmoris DSM 12784T were 27.4 and 83.9 %, respectively. Based on phenotypic, phylogenetic and genotypic data, a novel species, named Deinococcus arenicola sp. nov., is proposed. The type strain iis ZS9-10T (=CCTCC AB 2019392T=KCTC43192T).

Quorum sensing signal autoinducer-2 promotes hydrogen peroxide degradation in water by Gram-positive bacteria

Hydrogen peroxide is widely used to remedy bacterial and parasitic infections, but its excessive use will cause severe damage to aquatic animals. Moreover, there is no safe, efficient and low-cost method to degrade residual hydrogen peroxide in water. Here we developed a hydrogen peroxide removal mechanism by which autoinducer-2 (AI-2), a quorum sensing signal molecule that can promote the hydrogen peroxide degradation by Gram-positive bacteria. Here, we investigated the promotion effect of AI-2 on hydrogen peroxide degradation by Deinococcus sp. Y35 and the response of the antioxidant system. We further sought to understand the key mechanism underlying the promotion effect of AI-2 on hydrogen peroxide degradation is that, AI-2 contributed to the resistance of strain Y35 to oxidative stress induced by hydrogen peroxide, and altered membrane permeability of strain Y35 that allowed more hydrogen peroxide to enter bacterial cells and be degraded. Additionally, AI-2 can also encourage multiple Gram-positive bacteria to degrade hydrogen peroxide. Accordingly, our study serves as a reference for the regulation mechanism of the signal molecule AI-2 and provides the development of new strategies for hydrogen peroxide degradation.