National Institute for Public Health and the Environment, Centre for Infectious Disease Control, Laboratory for Zoonoses and Environmental Microbiology, Bilthoven, The Netherlands.
FEMS Microbiol Lett. 2013 Jan;338(1):18-23. doi: 10.1111/1574-6968.12024. Epub 2012 Nov 8.
Although it is known that Escherichia coli O157 is capable of long-term soil survival, little is known about the mechanisms involved. This study investigated the role of the general stress response system RpoS in E. coli soil survival. The results showed that E. coli O157 isolates capable of long-term survival (longer than 200 days) in manure-amended soil were characterized by the absence of mutations in their rpoS gene. In contrast, the strains not capable of long-term survival all possessed mutations in their rpoS gene. In addition, the long-term surviving strains showed significantly higher levels of acid resistance in simulated gastric fluid (pH 2.5). Sequencing of the rpoS gene of bovine, food and clinical isolates revealed a skewed distribution of rpoS wild-type and mutant strains among the different sources. Bovine and food isolates had low numbers of mutants (< 1.4 and 6.9%, respectively), while a relatively high number of mutants was observed among human isolates (32.9%). The results indicate that a fully functional RpoS system is an advantage for survival in the manure-amended soil environment. Further deletion and complementation studies should provide more evidence on the role of RpoS in the long-term survival of E. coli O157 in diverse environments.
尽管已知大肠杆菌 O157 能够在土壤中长期存活，但对于涉及的机制却知之甚少。本研究调查了普遍应激反应系统 RpoS 在大肠杆菌土壤存活中的作用。结果表明，能够在粪便改良土壤中长时间存活（超过 200 天）的大肠杆菌 O157 分离株的 rpoS 基因没有突变。相比之下，不能长时间存活的菌株的 rpoS 基因都发生了突变。此外，长期存活的菌株在模拟胃液（pH 2.5）中表现出明显更高的酸抗性水平。对牛、食品和临床分离株的 rpoS 基因进行测序显示，rpoS 野生型和突变型菌株在不同来源中的分布存在偏倚。牛和食品分离株的突变体数量较少（分别为<1.4%和 6.9%），而人类分离株中观察到相对较高数量的突变体（32.9%）。结果表明，功能齐全的 RpoS 系统是在粪便改良土壤环境中生存的优势。进一步的缺失和互补研究应该为 RpoS 在大肠杆菌 O157 在不同环境中的长期存活中的作用提供更多证据。
