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内容記述 |
Rubrobacter spp., members of the phylum Actinobacteria, are known for their resistance to radiation but are phylogenetically distinct from Deinococcus spp., the most extensively studied radiation-resistant bacteria. Several thermophilic Rubrobacter species capable of growing above 55°C have been reported, including strain AA3-22 that was isolated from the Arima hot spring (optimum growth temperature: 58°C). In contrast to Deinococcus, where intra-genus variations in radiation resistance have been described, comparative studies on mutagen resistance in Rubrobacter spp. are scarce.In this study, we examined the resistance of thermophilic Rubrobacter strains, AA3-22, R. xylanophilus PRD-1, R. calidifluminis RG-1, and R. naiadicus RG-3, under identical growth conditions. Survival was measured after treatments with gamma-rays (4–20 kGy), UV-C light (50–500 J/m²), and mitomycin C (100 µg/mL, 30–180 min). Cells were serially diluted, plated on CYC agar, and incubated at 60°C before counting the colony numbers.AA3-22 and PRD-1 showed similar resistance to gamma rays and UV-C light, while RG-1 and RG-3 were more sensitive. However, the four strains varied in their sensitivity to mitomycin C, with PRD-1 being the most resistant. These results suggest that resistance to gamma rays and UV-C light may reflect phylogenetic relationships, while differences in mitomycin C sensitivity indicate functional diversity in DNA repair pathways. Ongoing genome analyses aim to identify candidate genes involved in the repair of DNA damage induced by mitomycin C. |
