Hauben K J, Bartlett D H, Soontjens C C, Cornelis K, Wuytack E Y, Michiels C W
Laboratory of Food Microbiology, Katholieke Universiteit Leuven, Belgium.
Appl Environ Microbiol. 1997 Mar;63(3):945-50. doi: 10.1128/aem.63.3.945-950.1997.
Alternating cycles of exposure to high pressure and outgrowth of surviving populations were used to select for highly pressure-resistant mutants of Escherichia coli MG1655. Three barotolerant mutants (LMM1010, LMM1020, and LMM1030) were isolated independently by using outgrowth temperatures of 30, 37, and 42 degrees C, respectively. Survival of these mutants after pressure treatment for 15 min at ambient temperature was 40 to 85% at 220 MPa and 0.5 to 1.5% at 800 MPa, while survival of the parent strain, MG1655, decreased from 15% at 220 MPa to 2 x 10(-8)% at 700 MPa. Heat resistance of mutants LMM1020 and LMM1030 was also altered, as evident by higher D values at 58 and 60 degrees C and reduced z values compared to those for the parent strain. D and z values for mutant LMM1010 were not significantly different from those for the parent strain. Pressure sensitivity of the mutants increased from 10 to 50 degrees C, as opposed to the parent strain, which showed a minimum around 40 degrees C. The ability of the mutants to grow at moderately elevated pressure (50 MPa) was reduced at temperatures above 37 degrees C, indicating that resistance to pressure inactivation is unrelated to barotolerant growth. The development of high levels of barotolerance as demonstrated in this work should cause concern about the safety of high-pressure food processing.
通过交替进行高压暴露和存活群体的生长，来筛选大肠杆菌MG1655的高度耐压突变体。分别采用30、37和42摄氏度的生长温度，独立分离出三个耐压突变体（LMM1010、LMM1020和LMM1030）。在环境温度下对这些突变体进行15分钟压力处理后，在220兆帕时其存活率为40%至85%，在800兆帕时为0.5%至1.5%，而亲本菌株MG1655在220兆帕时的存活率从15%降至700兆帕时的2×10⁻⁸%。突变体LMM1020和LMM1030的耐热性也发生了改变，与亲本菌株相比，在58和60摄氏度时D值更高，z值更低，这一点很明显。突变体LMM1010的D值和z值与亲本菌株没有显著差异。与亲本菌株在40摄氏度左右出现最小值不同，突变体在10至50摄氏度时压力敏感性增加。突变体在高于37摄氏度的温度下，在中等升高压力（50兆帕）下生长的能力降低，这表明对压力失活的抗性与耐压生长无关。这项工作中所展示的高水平耐压性的发展，应该引起人们对高压食品加工安全性的关注。
