Bacillus subtilis is a vital component of the gut microbiome and can play a role in repairing damaged intestinal tissues and improving symptoms such as those of inflammatory bowel disease (IBD). The bacteria can be used in the form of spores. Some of the available methods for producing Bacillus subtilis spores are complex and time-consuming, requiring specific pH values, temperatures, or pressures, and/or tedious post-processing procedures.

Zheng Zhao, The Chinese University of Hong Kong, Shenzhen (CUHK-Shenzhen), Guangdong, China, and HKUST-Shenzhen Research Institute, China, Ben Zhong Tang, CUHK-Shenzhen, HKUST-Shenzhen Research Institute, and The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China, and colleagues have utilized the singlet oxygen production of the photosensitizer TBPBB (pictured in red) to induce the transformation of Bacillus subtilis vegetative cells into spores. The transformation takes place at room temperature and ambient pressure upon short-term exposure to white light.

When the newly formed spores reach an area of damaged tissue in the intestines, they transform into active Bacillus subtilis vegetative cells. The germination process, along with the subsequent reactivation of the bacteria and metabolic activities, will result in the decomposition of sugars, release of water and carbon dioxide, and the production of lactic acid/acetic acid that help regulate the gut environment and facilitate the repair of the damaged intestinal barrier.

Throughout the bio-transformation process of Bacillus subtilis from vegetative cells to spores and back to reactivated cells, the photosensitizer TBPBB still labels the cells, producing a fluorescent signal that can be used to directly observe and assess the effects, with comparable efficiency to traditional staining methods.

• Photo‐induced Bacillus subtilis‐spore transformation for bowel disease therapy and therapeutic outcome visualization,
  Lin Kong, Wei He, Junyi Gong, Zijie Qiu, Zheng Zhao, Ben Zhong Tang,
  Aggregate 2024.
  https://doi.org/10.1002/agt2.597