Byrd J J, Cheville A M, Bose J L, Kaspar C W
Department of Biology, St. Mary's College of Maryland, St. Mary's City, Maryland 20686, USA.
Appl Environ Microbiol. 1999 Jun;65(6):2396-401. doi: 10.1128/AEM.65.6.2396-2401.1999.
A by-product of glucose produced during sterilization (121 degrees C, 15 lb/in2, 15 min) at neutral pH and in the presence of phosphate (i.e., phosphate-buffered saline) was bactericidal to Escherichia coli O157:H7 (ATCC 43895). Other six-carbon (fructose and galactose) and five-carbon (arabinose, ribose, and xylose) reducing sugars also produced a toxic by-product under the same conditions. Fructose and the five-carbon sugars yielded the most bactericidal activity. Glucose concentrations of 1% (wt/vol) resulted in a 99.9% decline in the CFU of stationary-phase cells per milliliter in 2 days at 25 degrees C. An rpoS mutant (pRR10::rpoS) of strain 43895 (FRIK 816-3) was significantly (P < 0.001) more sensitive to the glucose-phosphate by-product than the parent strain, as glucose concentrations from 0.05 to 0.25% resulted in a 2- to 3-log10 reduction in CFU per milliliter in 2 days at 25 degrees C. Likewise, log-phase cells of the wild-type strain, 43895, were significantly more sensitive (P < 0.001) to the glucose-phosphate by-product than were stationary-phase cells, which is consistent with the stability of rpoS and the regulation of rpoS-regulated genes. The bactericidal effect of the glucose-phosphate by-product was reduced when strains ATCC 43895 and FRIK 816-3 were incubated at a low temperature (4 degrees C). Also, growth in glucose-free medium (i.e., nutrient broth) did not alleviate the sensitivity to the glucose-phosphate by-product and excludes the possibility of substrate-accelerated death as the cause of the bactericidal effect observed. The glucose-phosphate by-product was also bactericidal to Salmonella typhimurium, Shigella dysenteriae, and a Klebsiella sp. Attempts to identify the glucose-phosphate by-product were unsuccessful. These studies demonstrate the production of a glucose-phosphate by-product bactericidal to E. coli O157:H7 and the protective effects afforded by rpoS-regulated gene products. Additionally, the detection of sublethally injured bacteria may be compromised by the presence of this by-product in recovery media.
在中性pH值且存在磷酸盐（即磷酸盐缓冲盐水）的条件下，于121摄氏度、15磅/平方英寸压力下灭菌15分钟时产生的葡萄糖副产物对大肠杆菌O157:H7（ATCC 43895）具有杀菌作用。其他六碳糖（果糖和半乳糖）和五碳糖（阿拉伯糖、核糖和木糖）在相同条件下也会产生有毒副产物。果糖和五碳糖产生的杀菌活性最强。1%（重量/体积）的葡萄糖浓度在25摄氏度下2天内可使每毫升稳定期细胞的CFU下降99.9%。菌株43895（FRIK 816 - 3）的rpoS突变体（pRR10::rpoS）对葡萄糖 - 磷酸盐副产物的敏感性显著高于亲本菌株（P < 0.001），因为在25摄氏度下，0.05%至0.25%的葡萄糖浓度在2天内可使每毫升CFU降低2至3个对数级。同样，野生型菌株43895的对数期细胞对葡萄糖 - 磷酸盐副产物的敏感性也显著高于稳定期细胞（P < 0.001），这与rpoS的稳定性以及rpoS调控基因的调节作用一致。当将ATCC 43895和FRIK 816 - 3菌株在低温（4摄氏度）下培养时，葡萄糖 - 磷酸盐副产物的杀菌作用减弱。此外，在无葡萄糖培养基（即营养肉汤）中生长并不能减轻对葡萄糖 - 磷酸盐副产物的敏感性，排除了底物加速死亡是观察到的杀菌作用原因的可能性。葡萄糖 - 磷酸盐副产物对鼠伤寒沙门氏菌、痢疾志贺氏菌和一种克雷伯氏菌也具有杀菌作用。鉴定葡萄糖 - 磷酸盐副产物的尝试未成功。这些研究证明了产生了对大肠杆菌O157:H7具有杀菌作用的葡萄糖 - 磷酸盐副产物以及rpoS调控基因产物所提供的保护作用。此外，在复苏培养基中存在这种副产物可能会影响对亚致死损伤细菌的检测。
