Apetroaie-Constantin Camelia, Shaheen Ranad, Andrup Lars, Smidt Lasse, Rita Hannu, Salkinoja-Salonen Mirja
University of Helsinki, Department of Applied Chemistry and Microbiology, P.O. Box 56, Viikinkaari 9, FI-00014 Helsinki, Finland.
Int J Food Microbiol. 2008 Sep 30;127(1-2):60-7. doi: 10.1016/j.ijfoodmicro.2008.06.006. Epub 2008 Jun 12.
The impacts of growth media and temperature on production of cereulide, the emetic toxin of Bacillus cereus, were measured for seven well characterised strains selected for diversity of biochemical and genetic properties and sources of origin. All strains carried cereulide synthase gene, ces, on a megaplasmid of ca. 200 kb and all grew up to 48-50 degrees C, but produced cereulide only up to 39 degrees C. On tryptic soy agar five strains, originating from foods, food poisonings and environment, produced highest amounts of cereulide at 23 to 28 degrees C, whereas two strains, from human faeces, produced cereulide similarly from 23 to 39 degrees C, with no clear temperature trend. These two strains differed from the others also by producing more cereulide on tryptic soy agar if supplemented with 5 vol.% of blood, whereas the other five strains produced similarly, independent on the presence of blood. On oatmeal agar only one strain produced major amounts of cereulide. On skim milk agar, raw milk agar, and MacConkey agar most strains grew well but produced only low amounts of cereulide. Three media components, the ratio [K+]:[Na+], contents of glycine and [Na+], appeared of significance for predicting cereulide production. Increase of [K+]:[Na+] (focal variable) predicted (P < 0.001) high cereulide provided that the contents of glycine and [Na+] (additional variables) were kept constant. The results show that growth medium and temperature up and downregulate cereulide production by emetic B. cereus in a complex manner. The relevance of the findings to production of cereulide in the gut and to the safety of amino acids as additives in foods containing live toxinogenic organisms is discussed.
针对七株具有不同生化特性、遗传特性及来源的芽孢杆菌进行了研究，测定了生长培养基和温度对蜡样芽孢杆菌呕吐毒素cereulide产生的影响。所有菌株的cereulide合成酶基因ces位于约200 kb的大质粒上，且都能在高达48 - 50摄氏度的环境下生长，但仅在39摄氏度以下产生cereulide。在胰蛋白胨大豆琼脂培养基上，五株分别来源于食品、食物中毒事件及环境的菌株在23至28摄氏度时产生的cereulide量最高，而两株来源于人类粪便的菌株在23至39摄氏度时产生cereulide的情况相似，无明显温度趋势。这两株菌株与其他菌株的不同之处还在于，在添加5%（体积分数）血液的胰蛋白胨大豆琼脂培养基上能产生更多的cereulide，而其他五株菌株产生的量相似，与血液的存在与否无关。在燕麦片琼脂培养基上，只有一株菌株产生大量的cereulide。在脱脂乳琼脂、生乳琼脂和麦康凯琼脂培养基上，大多数菌株生长良好，但仅产生少量的cereulide。三种培养基成分，即[K⁺]:[Na⁺]的比例、甘氨酸含量和[Na⁺]含量，对于预测cereulide的产生具有重要意义。在甘氨酸含量和[Na⁺]含量（附加变量）保持恒定的情况下，[K⁺]:[Na⁺]（焦点变量）的增加可预测（P < 0.001）高产量的cereulide。结果表明，生长培养基和温度以复杂的方式上调和下调呕吐型蜡样芽孢杆菌cereulide的产生。本文还讨论了这些发现与肠道中cereulide产生以及含有活产毒生物体的食品中氨基酸作为添加剂的安全性之间的相关性。
