Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
Microbiologyopen. 2020 May;9(5):e1015. doi: 10.1002/mbo3.1015. Epub 2020 Mar 5.
Listeria monocytogenes is the causative agent of human listeriosis which has high hospitalization and mortality rates for individuals with weakened immune systems. The survival and dissemination of L. monocytogenes in adverse environments can be reinforced by the formation of biofilms. Therefore, this study aimed to understand the mechanisms underlying listerial biofilm development. Given that both nutrient availability and quorum sensing (QS) have been known as the factors influencing biofilm development, we hypothesized that the signal from a sentinel metabolite S-adenosylmethionine (SAM) and Agr-based QS could be synchronous in L. monocytogenes to modulate nutrient availability, the synthesis of extracellular polymeric substances (EPSs), and biofilm formation. We performed biofilm assays and quantitative real-time PCR to investigate how biofilm volumes and the expression of genes for the synthesis of EPS were affected by SAM supplementation, agr deletion, or both. We found that exogenously applied SAM induced biofilm formation and that the expression of genes encoding the EPS synthesis machineries was regulated by SAM and/or Agr QS. Moreover, the gene transcription of components acting in the methyl cycle for SAM synthesis and Agr QS was affected by the signals from the other system. In summary, we reveal an interconnection at the transcriptional level between metabolism and QS in L. monocytogenes and highlight the critical role of metabolite-oriented QS in biofilm development.
李斯特菌是人类李斯特菌病的病原体，对于免疫系统较弱的个体，其住院率和死亡率都很高。李斯特菌可以通过生物膜的形成来增强其在不利环境中的生存和传播能力。因此，本研究旨在了解李斯特菌生物膜形成的机制。鉴于营养物质的可用性和群体感应（QS）都被认为是影响生物膜形成的因素，我们假设哨兵代谢物 S-腺苷甲硫氨酸（SAM）和 Agr 基 QS 的信号可以在李斯特菌中同步，以调节营养物质的可用性、细胞外聚合物质（EPS）的合成和生物膜的形成。我们进行了生物膜测定和定量实时 PCR 实验，以研究 SAM 补充、agr 缺失或两者对生物膜体积和 EPS 合成基因表达的影响。我们发现，外源性 SAM 诱导生物膜形成，并且 EPS 合成机制的基因表达受到 SAM 和/或 Agr QS 的调节。此外，SAM 合成和 Agr QS 中甲基循环作用成分的基因转录受到另一个系统信号的影响。总之，我们揭示了李斯特菌代谢和 QS 在转录水平上的相互联系，并强调了代谢物导向的 QS 在生物膜形成中的关键作用。
