Excessive ultraviolet C irradiation causes spore protein denaturation and prohibits the initiation of spore germination in Bacillus subtilis.

Ultraviolet (UV) -C is widely used to kill bacteria as it damages chromosomal DNA. We analyzed the denaturation of the protein function of Bacillus subtilis spores after UV-C irradiation. Almost all of the B. subtilis spores germinated in Luria-Bertani (LB) liquid medium, but the colony-forming unit (CFU) of the spores on LB agar plates decreased to approximately 1/103 by 100 mJ/cm2 of UV-C irradiation. Some of the spores germinated in LB liquid medium under phase-contrast microscopy, but almost no colonies formed on the LB agar plates after 1 J/cm2 of UV-C irradiation. The fluorescence of the green fluorescent protein (GFP) -fused spore proteins, YeeK-GFP, YeeK is a coat protein, decreased following UV-C irradiation of over 1 J/cm2, while that of SspA-GFP, SspA is a core protein, decreased following UV-C irradiation of over 2 J/ cm2, respectively. These results revealed that UV-C affected on coat proteins more than core proteins. We conclude that 25 to 100 mJ/cm2 of UV-C irradiation can cause DNA damage, and more than 1 J/cm2 of UV-C irradiation can cause the denaturation of spore proteins involved in germination. Our study would contribute to improve the technology to detect the bacterial spores, especially after UV sterilization.

Citation

Ritsuko Kuwana, Ryuji Yamazawa, Ryoko Asada, Kiyoshi Ito, Masakazu Furuta, Hiromu Takamatsu. Excessive ultraviolet C irradiation causes spore protein denaturation and prohibits the initiation of spore germination in Bacillus subtilis. Journal of microorganism control. 2023;28(1):15-25

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PMID: 37277954

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