Nguyen Thi Minh Hue, Guyot Stéphane, Perrier-Cornet Jean-Marie, Gervais Patrick
Laboratoire de Génie des Procédés Microbiologiques et Alimentaires, ENSBANA, Université de Bourgogne, 1 Esplanade Erasme, Dijon, France.
Appl Microbiol Biotechnol. 2008 Aug;80(1):107-14. doi: 10.1007/s00253-008-1519-x. Epub 2008 May 28.
The causes of Bacillus spore resistance remain unclear. Many structures including a highly compact envelope, low hydration of the protoplast, high concentrations of Ca-chelated dipicolinic acid, and the presence of small acid-soluble spore proteins seem to contribute to resistance. To evaluate the role of internal protoplast composition and hydration, spores of Bacillus subtilis were produced at different osmotic pressures corresponding to water activities of 0.993 (standard), 0.970, and 0.950, using the two depressors (glycerol or NaCl). Sporulation of Bacillus subtilis was slower and reduced in quantity when the water activity was low, taking 4, 10, and 17 days for 0.993, 0.970, and 0.950 water activity, respectively. The spores produced at lower water activity were smaller and could germinate on agar medium at lower water activity than on standard spores. They were also more sensitive to heat (97 degrees C for 5-60 min) than the standard spores but their resistance to high hydrostatic pressure (350 MPa at 40 degrees C for 20 min to 4 h) was not altered. Our results showed that the water activity of the sporulation medium significantly affects spore properties including size, germination capacity, and resistance to heat but has no role in bacterial spore resistance to high hydrostatic pressure.
芽孢杆菌孢子抗性的原因尚不清楚。许多结构，包括高度紧密的包膜、原生质体的低水合作用、高浓度的钙螯合吡啶二羧酸以及小的酸溶性孢子蛋白的存在，似乎都有助于抗性。为了评估内部原生质体组成和水合作用的作用，使用两种降压剂（甘油或氯化钠）在对应于水活度为0.993（标准）、0.970和0.950的不同渗透压下产生枯草芽孢杆菌的孢子。当水活度较低时，枯草芽孢杆菌的芽孢形成较慢且数量减少，水活度为0.993、0.970和0.950时分别需要4天、10天和17天。在较低水活度下产生的孢子较小，并且在较低水活度的琼脂培养基上比标准孢子更容易萌发。它们对热（97摄氏度，5至60分钟）也比标准孢子更敏感，但它们对高静水压（40摄氏度下350兆帕，20分钟至4小时）的抗性没有改变。我们的结果表明，芽孢形成培养基的水活度显著影响孢子特性，包括大小、萌发能力和耐热性，但对细菌孢子对高静水压的抗性没有影响。
