Cerca Nuno, Jefferson Kimberly K
Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA, USA.
FEMS Microbiol Lett. 2008 Jun;283(1):36-41. doi: 10.1111/j.1574-6968.2008.01142.x.
Escherichia coli contains a four-gene operon, pgaABCD, which encodes the proteins necessary for the synthesis of polymeric N-acetylglucosamine, or PGA. Poly-N-acetyl-glucosamine was first described in Staphylococcus aureus and Staphylococcus epidermidis and was found to have important roles in biofilm formation and immune evasion. PGA also plays a role in biofilm formation in E. coli, but its role in immune evasion has not been thoroughly studied. We previously reported that E. coli PGA cross-reacts with an opsonic-antibody raised against S. aureus PNAG and this is the basis for an ongoing investigation regarding the development of a vaccine against both pathogens. In this paper we investigated pga expression in wild type and csrA or nhaR deletion mutant strains during different growth phases and temperatures, and in response to chemical stimuli using a pga promoter-reporter fusion construct, real-time reverse transcriptase-PCR, immunoblotting, and biofilm assays. Expression of pga and polysaccharide synthesis were induced by glucose, NaCl, and ethanol, but only glucose augmented biofilm formation. The regulatory factor NhaR was required for NaCl-induced pga expression, whereas the effects of glucose and ethanol were independent of CsrA and NhaR.
大肠杆菌含有一个四基因操纵子pgaABCD，它编码合成聚合N-乙酰葡糖胺（或PGA）所需的蛋白质。聚N-乙酰葡糖胺最早在金黄色葡萄球菌和表皮葡萄球菌中被描述，发现其在生物膜形成和免疫逃避中起重要作用。PGA在大肠杆菌的生物膜形成中也起作用，但其在免疫逃避中的作用尚未得到充分研究。我们之前报道过大肠杆菌PGA与针对金黄色葡萄球菌PNAG产生的调理抗体发生交叉反应，这是目前针对这两种病原体开发疫苗研究的基础。在本文中，我们使用pga启动子-报告基因融合构建体、实时逆转录-聚合酶链反应、免疫印迹和生物膜测定法，研究了野生型以及csrA或nhaR缺失突变株在不同生长阶段和温度下，以及对化学刺激作出反应时pga的表达情况。pga的表达和多糖合成受到葡萄糖、氯化钠和乙醇的诱导，但只有葡萄糖增强了生物膜的形成。调节因子NhaR是氯化钠诱导pga表达所必需的，而葡萄糖和乙醇的作用则独立于CsrA和NhaR。
