Ryan Sheila, Begley Máire, Gahan Cormac G M, Hill Colin
Department of Microbiology, University College Cork, Cork, Ireland.
Environ Microbiol. 2009 Feb;11(2):432-45. doi: 10.1111/j.1462-2920.2008.01782.x.
The capacity of Listeria monocytogenes to withstand low pH is important for growth in low-pH foods, successful passage through the gastric barrier and survival within the macrophage phagosome. The ability of this pathogen to survive and adapt to acidic conditions is therefore predicted to play a significant role in the infectious cycle. In silico analysis of the L. monocytogenes genome revealed the presence of putative arginine deiminase (ADI) genes, which have been shown to play a role in the acid tolerance of other bacterial genera. In the present study, we show that L. monocytogenes possesses a functional ADI system and analysis of deletion mutants reveals that it contributes to both growth and survival of the bacterium under acidic conditions. An RT-PCR approach demonstrated that expression of ADI genes is increased in environments of low pH and anaerobicity and in the presence of arginine. A putative activator of ADI genes, namely ArgR, was identified and was shown to contribute to transcriptional regulation at this locus. Furthermore, expression of ADI genes was shown to be modulated by both the alternative stress sigma factor sigma(B) and the central virulence regulator PrfA. Finally, using the murine model of infection, we have established a role for the ADI system in the virulence of L. monocytogenes.
单核细胞增生李斯特菌耐受低pH值的能力对于其在低pH值食品中的生长、成功穿越胃屏障以及在巨噬细胞吞噬体内存活至关重要。因此，预计这种病原体在酸性条件下存活和适应的能力在感染周期中发挥重要作用。对单核细胞增生李斯特菌基因组的计算机分析揭示了假定的精氨酸脱亚胺酶（ADI）基因的存在，这些基因已被证明在其他细菌属的耐酸性中发挥作用。在本研究中，我们表明单核细胞增生李斯特菌拥有功能性的ADI系统，对缺失突变体的分析表明它有助于细菌在酸性条件下的生长和存活。一种逆转录聚合酶链反应（RT-PCR）方法表明，ADI基因的表达在低pH值和厌氧环境以及存在精氨酸的情况下会增加。鉴定出一种假定的ADI基因激活剂，即ArgR，并表明它有助于该位点的转录调控。此外，已证明ADI基因的表达受替代应激σ因子σ(B)和中心毒力调节因子PrfA的调节。最后，使用小鼠感染模型，我们确定了ADI系统在单核细胞增生李斯特菌毒力中的作用。
