Temperature dependence of Bacillus cereus spores: effects on sporulation, germination behavior, and inner membrane protein responses.

Abstract

Bacillus cereus, a prevalent foodborne pathogen, produces dormant spores that can persist throughout meat preservation. Upon germination and growth, it causes meat spoilage and human illness. Since bacterial spore properties are highly temperature-dependent, this study investigated the effects of temperature on sporulation, germination behavior, and the responses of inner membrane proteins (IMPs). Spores with high germination efficiency were readily formed at 25-30 °C, with the highest efficiency observed at 30 °C. Meanwhile, analysis of spore properties showed that higher sporulation temperatures resulted in lower spore water content and greater resistance to moist heat. Raman spectroscopy further revealed temperature-dependent variations in the molecular characteristics of intact spores, including changes associated with Ca2+-dipicolinic acid (Ca2+-DPA), protein-related, and nucleic acid-related spectral features under different sporulation temperatures. Different heat activation temperatures resulted in distinct spore germination efficiency and induced physicochemical changes inextracted IMPs fractions. Notably, 65 °C represented the optimum heat activation condition across 60-80 °C, resulting in enhanced germination efficiency and moderate conformational rearrangement of IMPs, as characterized by complementary biophysical analyses. These findings highlight the importance of temperature control in regulating spore germination and inactivation during food processing and provide practical insights for the management of bacterial spores in the food industry.