Center for Food Safety and Department of Food Science and Technology, University of Georgia, 1109 Experiment Street, Griffin, Georgia 30223-1797, USA.
J Food Prot. 2005 Aug;68(8):1734-8. doi: 10.4315/0362-028x-68.8.1734.
A study was done to determine the effect of interacting factors on sporulation of Bacillus cereus in broth. Vegetative cells (1.4 to 2.2 log CFU/ml) of B. cereus strain 038-2 (capable of growing at 12 degrees C) and strain F3812/84 (capable of growing at 8 degrees C) were inoculated into 30 ml of tryptic soy broth (TSB), TSB supplemented with manganese (50 microg/ml), diluted (10%) TSB (dTSB), and dTSB supplemented with manganese (50 microg/ml) and incubated at 8, 12, or 22 degrees C for up to 30, 30, or 10 days, respectively. Unheated and heated (80 degrees C for 10 min) cultures were plated on brain heart infusion agar to determine total cell counts (vegetative cells plus spores) and the number of spores produced, respectively. Both strains of B. cereus survived in TSB and dTSB for 30 days at 8 degrees C but did not sporulate. At 12 degrees C, cells grew in TSB to a population of 6.0 +/- 0.8 log CFU/ml, which was maintained for 30 days. Neither strain grew in dTSB at 12 degrees C and survived for at least 30 days. Spores were not produced in any of the test broths at 12 degrees C. At 22 degrees C, cells reached a stationary growth phase between 12 and 24 h in TSB, TSB supplemented with manganese, and dTSB supplemented with manganese, and approximately 1% of the CFU were spores. In dTSB, cell growth and spore formation were retarded at 22 degrees C and a significantly lower number of spores was produced compared with the number of spores produced in TSB, TSB supplemented with manganese, and dTSB supplemented with manganese. The addition of manganese to TSB did not affect cell growth or spore formation, but manganese did enhance sporulation in dTSB. This study provides useful information on spore formation by B. cereus as affected by conditions that may be imposed in liquid milieus on the surface of foods and on food contact surfaces in processing environments.
一项研究旨在确定交互因素对芽孢杆菌在肉汤中孢子形成的影响。将芽孢杆菌 038-2 菌株（能够在 12°C 下生长）和 F3812/84 菌株（能够在 8°C 下生长）的营养细胞（1.4 至 2.2 log CFU/ml）接种到 30 毫升胰蛋白酶大豆肉汤（TSB）、TSB 中添加锰（50μg/ml）、稀释（10%）TSB（dTSB）和 dTSB 中添加锰（50μg/ml）中，并分别在 8°C、12°C 或 22°C 下孵育长达 30、30 或 10 天。未加热和加热（80°C 加热 10 分钟）的培养物在脑心浸出琼脂平板上平板，分别确定总细胞计数（营养细胞加孢子）和产生的孢子数。两种芽孢杆菌在 8°C 的 TSB 和 dTSB 中均可存活 30 天，但不产孢。在 12°C 下，细胞在 TSB 中生长至 6.0 +/- 0.8 log CFU/ml 的群体，可维持 30 天。在 12°C 下，两种菌株均不能在 dTSB 中生长，并至少存活 30 天。在 12°C 的任何测试肉汤中均未产生孢子。在 22°C 下，细胞在 TSB、TSB 中添加锰和 dTSB 中添加锰中在 12 至 24 小时达到静止生长阶段，约 1%的 CFU 为孢子。在 22°C 下，dTSB 中的细胞生长和孢子形成受到抑制，与 TSB、TSB 中添加锰和 dTSB 中添加锰中产生的孢子数量相比，产生的孢子数量明显减少。在 TSB 中添加锰不会影响细胞生长或孢子形成，但锰确实增强了 dTSB 中的孢子形成。本研究提供了有关芽孢杆菌孢子形成的有用信息，这些信息受食品表面液体环境中和加工环境中食品接触表面上可能施加的条件的影响。
