Bicarbonate ion stimulates the expression of locus of enterocyte effacement-encoded genes in enterohemorrhagic Escherichia coli O157:H7
Bicarbonate ion stimulates the expression of locus of enterocyte effacement-encoded genes in enterohemorrhagic Escherichia coli O157:H7
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DOI：
10.1128/iai.70.7.3500-3509.2002
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发表时间：
2002-07-01
影响因子：
3.1
通讯作者：
Sasakawa, C
中科院分区：
文献类型：
--
作者：
Abe, H;Tatsuno, I;Sasakawa, C
肠出血性大肠杆菌（EHEC）菌株粘附于肠粘膜并产生附着和消退（A/E）损伤。大多数产生A/E病变所需的基因被认为是由36-kb的致病岛编码的，称为肠上皮细胞消失位点（LEE）。虽然细菌粘附的机制，包括相关的基因，仍然知之甚少，肠出血性大肠杆菌的优先粘附表型被认为取决于基因的性质和/或这些基因对环境条件变化的反应。为了探索影响肠出血性大肠杆菌粘附的环境因素，我们使用了O 157：117菌株，并研究了其粘附Caco-2细胞的最佳生长条件。我们观察到在Dulbecco改良Eagle培养基（DMEM）中生长的EHEC比在Luria-Bertani（LB）肉汤中生长的EHEC更有效地粘附于Caco-2细胞。在DMEM的成分中，发现只有NaHCO 3显著刺激细菌粘附。当细菌在含有NaHCO 3的LB肉汤中生长时，与LB肉汤中的生产相比，紧密素、Tir、EspA和EspB的生产大大增强。事实上，LEE编码的基因表达所需的LER的转录响应于LB肉汤中NaHCO 3的浓度而得到促进。由于NaHCO 3在下肠道中的浓度相对较高，与上小肠相比，我们的结果可能意味着NaHCO 3是促进EHEC在人类下肠道定植的重要信号因子。
Enterohemorrhagic Escherichia coli (EHEC) strains adhere to the intestinal mucosa and produce an attaching and effacing (A/E) lesion. Most of the genes required to produce A/E lesions are thought to be encoded by the 36-kb pathogenicity island termed the locus for enterocyte effacement (LEE). Although the mechanisms underlying the bacterial adherence, including the genes involved, are still poorly understood, the preferential adherence phenotype of EHEC is thought to depend on the nature of the genes and/or the response of these genes to changes in environmental conditions. To explore the environmental factors affecting EHEC adherence, we used an O157:117 strain and investigated the optimal growth conditions for its adherence to Caco-2 cells. We observed that EHEC grown in Dulbecco's modified Eagle's medium (DMEM) adhered more efficiently to Caco-2 cells than EHEC grown in Luria-Bertani (LB) broth. Among the components of DMEM, only NaHCO3 was found to remarkably stimulate bacterial adherence. When bacteria were grown in LB broth containing NaHCO3 the production of intimin, Tir, EspA, and EspB was greatly enhanced compared with the production in LB broth. Indeed, the transcription of ler required for LEE-encoded gene expression was promoted in response to the concentration of NaHCO3 in LB broth. Since the concentration of NaHCO3 in the lower intestinal tract has been shown to be relatively high compared with that in the upper small intestine, our results may imply that NaHCO3 is an important signaling factor for promoting colonization of EHEC in the lower intestinal tract in humans.