NaCl Influences Thermal Resistance and Cell Morphology of Escherichia coli Strains
NaCl Influences Thermal Resistance and Cell Morphology of Escherichia coli Strains
复制标题
DOI：
10.1111/jfs.12213
复制
发表时间：
2016-02
影响因子：
2.4
通讯作者：
Heeyoung Lee;Soomin Lee;Sejeong Kim;J. Ha;Jeeyeon Lee;Kyoung-Hee Choi;Y. Yoon
中科院分区：
文献类型：
--
作者：
Heeyoung Lee;Soomin Lee;Sejeong Kim;J. Ha;Jeeyeon Lee;Kyoung-Hee Choi;Y. Yoon
本研究阐明了氯化钠对大肠杆菌菌株耐热性和细胞形态的影响。大肠杆菌O157：H7 NCCP11142、大肠杆菌O111 ATCC12795和大肠杆菌O26 ATCC43887分别在35℃、0%氯化钠(未驯化)和2%和4%氯化钠(氯化钠驯化)的胰酶豆汤中培养。对未驯化、2%氯化钠驯化和4%氯化钠驯化的大肠杆菌O157：H7、大肠杆菌O111和大肠杆菌O26在50℃下进行热挑战。用实时定量聚合酶链式反应分析了与渗透胁迫相关的基因：β、OMPC、Prov、prow和与热应激相关的基因：clpB、dks A、dna J、dna K、GRPE、msbB、rpoE，并用场发射扫描电子显微镜观察了菌株的形态。热刺激后，O157：H7菌株的存活率明显高于其他菌株(P<；0.05)。Prov、prow和rpoE的表达水平随着盐浓度的增加而增加(P<；0.05)，但只有Prov的表达水平在不同菌株之间存在显著差异(P<；0.05)。结果表明，氯化钠对O157：H7的耐热性和细胞形态的影响与菌种有关，而提高Prov的表达水平可能是导致O157：H7菌株耐热性增强的原因。实际应用氯化钠在食品加工中被广泛用作抗菌剂和防腐剂。然而，大肠杆菌O157：H7在2%和4%的氯化钠中表现出耐热性，并上调了渗透和热相关基因的表达，并改变了细胞的形态。因此，应限制食品中的氯化钠浓度，以不增加大肠杆菌O157：H7对其他胁迫的耐受性。
This study elucidated the effect of NaCl on the thermal resistance and cell morphology of Escherichia coli strains. E. coli O157:H7 NCCP11142, E. coli O111 ATCC12795 and E. coli O26 ATCC43887 were incubated in tryptic soy broth formulated with 0% NaCl (nonhabituated) as well as broth formulated with 2% and 4% NaCl (NaCl-habituated) at 35C. Nonhabituated, 2% NaCl-habituated and 4% NaCl-habituated E. coli O157:H7, E. coli O111 and E. coli O26 were heat-challenged at 50C. The transcriptomes (osmotic stress-related: betA, ompC, proV, proW and heat stress-related: clpB, dksA, dnaJ, dnaK, grpE, msbB, rpoE) were analyzed using real-time polymerase chain reaction and the morphology of E. coli strains was also observed by field emission scanning electron microscopy. The survival of E. coli O157:H7 was higher (P < 0.05) than those of other strains after the heat challenge. The expression levels of proV, proW and rpoE increased (P < 0.05) as NaCl concentration increased, but only proV expression levels were significantly different (P < 0.05) among E. coli strains. The results indicate that the effect of NaCl on the thermal resistance and the cell morphology depends on the E. coli strain, and increased proV expression level by NaCl may cause the increased thermal resistance of E. coli O157:H7. Practical Applications NaCl is widely used as an antimicrobial and a preservative agent in food processing. However, Escherichia coli O157:H7 exposed to 2% and 4% NaCl showed thermal resistance, upregulated gene expression on osmotic- and heat-related genes and changed cell morphology. Thus, NaCl concentration should be limited in food not to increase E. coli O157:H7 tolerance to other stresses.