Coleman William H, Chen De, Li Yong-Qing, Cowan Ann E, Setlow Peter
Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305, USA.
J Bacteriol. 2007 Dec;189(23):8458-66. doi: 10.1128/JB.01242-07. Epub 2007 Sep 21.
Populations of Bacillus subtilis spores in which 90 to 99.9% of the spores had been killed by moist heat gave only two fractions on equilibrium density gradient centrifugation: a fraction comprised of less dense spores that had lost their dipicolinic acid (DPA), undergone significant protein denaturation, and were all dead and a fraction with the same higher density as that of unheated spores. The latter fraction from heat-killed spore populations retained all of its DPA, but >/=98% of the spores could be dead. The dead spores that retained DPA germinated relatively normally with nutrient and nonnutrient germinants, but the outgrowth of these germinated spores was significantly compromised, perhaps because they had suffered damage to some proteins such that metabolic activity during outgrowth was greatly decreased. These results indicate that DPA release takes place well after spore killing by moist heat and that DPA release during moist-heat treatment is an all-or-nothing phenomenon; these findings also suggest that damage to one or more key spore proteins causes spore killing by moist heat.
枯草芽孢杆菌孢子群体中，90%至99.9%的孢子已被湿热杀死，在平衡密度梯度离心时仅产生两个组分：一个组分由密度较低的孢子组成，这些孢子已失去其二吡啶甲酸（DPA），发生了显著的蛋白质变性，且全部死亡；另一个组分的密度与未加热的孢子相同。热杀死的孢子群体中的后一组分保留了其所有的DPA，但≥98%的孢子可能已死亡。保留DPA的死孢子在营养型和非营养型萌发剂作用下相对正常地萌发，但其萌发孢子的生长显著受损，这可能是因为它们的一些蛋白质受到了损伤，以至于生长过程中的代谢活性大大降低。这些结果表明，湿热杀死孢子后很久才会发生DPA释放，湿热处理期间的DPA释放是一种全或无的现象；这些发现还表明，对一种或多种关键孢子蛋白质的损伤会导致湿热杀死孢子。
