Effects of purity of spores of two Bacillus species on their resistance, germination and core CaDPA and water content

Authors: YE, FAITH - University Of Connecticut; SURYADEVARA, DHRUV - University Of Connecticut; KOLLU, UTTEJ - University Of Connecticut; BANNON, WILL - University Of Connecticut; KHAN, ZAARA - University Of Connecticut; KORZA, GEORGE - University Of Connecticut; WICANDER, JAMES - University Of Connecticut; Juneja, Vijay; SETLOW, PETER - University Of Connecticut

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: Human beings and our foodstuffs are continually in contact with these bacterial spores since they are ubiquitous in the environment. Previously, we reported that that the purity of spores affect the heat resistance of Bacillus subtilis and B. cereus spores. In this study, we assessed the resistance of spores purified to different degrees to UV radiation, formaldehyde, hydrogen peroxide, or sodium hypochlorite. Our results suggest that spore purity has no affect on their resistance to UV radiation or chemicals. The findings will be useful to companies in making decisions on interventions to be used to guard against the spores in processing environments as well as in processed foods.

Technical Abstract: A recent report (Juneja et al. 2024) showed that less well purified spores of two Bacillus and one Clostridium species were more wet heat resistant than well purified spores. The current work was with spores of a B. subtilis strain almost identical to the one used previously but with spores of a quite different B. cereus strain, and both with larger differences in their purity than used previously. The work found that the least purified B. subtilis spores, but not the new B. cereus strain’s spores, were significantly more wet heat resistant than the spores purified to different degrees. These findings indicate that it may be important to consider the purity of spores prepared as indicators for wet heat sterilization assurance, as the purity of the spores may be affecting their wet heat resistance, especially since large scale spore preparations are often not extensively purified. However, resistance to UV radiation, formaldehyde, hydrogen peroxide, or sodium hypochlorite were all relatively similar with the B. cereus or B. subtilis spores purified to different degrees. Thus, effects of other commonly used methods for spore inactivation, such as with hydrogen peroxide, may not be affected significantly by spore purity, at least with spores of the two Bacillus strains used in this work. Spores’ purity had minimal if any effects on rates of germinant-receptor dependent spore germination with different physiological germinants or germinant concentrations, and with dodecylamine that opens a channel protein leading to release of spore cores’ large pool of the 1:1 complex of Ca2+ and dipicolinic acid (CaDPA). Notably, the core water content in either B. cereus or B. subtilis spores purified to different degrees was almost identical, and spores of the same species purified to different degrees had nearly identical amounts of spore core CaDPA. Overall, these results do not yet allow assignment of any known causes for the higher wet heat resistance of cruder B. subtills spores.