Dorey Amber L, Lee Bo-Hyung, Rotter Bjorn, O'Byrne Conor P
Microbiology, School of Natural Sciences, Bacterial Stress Response Group, National University of Ireland Galway, Galway, Ireland.
GenXPro, Frankfurt am Main, Germany.
Front Microbiol. 2019 Nov 14;10:2497. doi: 10.3389/fmicb.2019.02497. eCollection 2019.
is an important food-borne pathogen that is tolerant to many of the stresses commonly used during food preservation. Outside the host, the bacterium has a saprophytic lifestyle that includes periodic exposure to solar irradiance. The blue component of this light is known to influence the activity of the stress-inducible sigma factor Sigma B (σ). In this study, the influence of temperature and growth phase on the response of to blue light was investigated and the global transcriptional response to blue light was elucidated using an RNAseq-based approach. Stationary phase cells were found to be significantly more resistant to killing by blue light (470 nm) than exponential phase cells. Temperature also had a marked effect on blue light resistance with cells cultured at 37°C being much more sensitive than cells grown at 30°C. The role of σ in light tolerance was confirmed but this effect was observed only at 30°C. σ activation by blue light was assessed by measuring the transcriptional response of known σ-dependent genes (, , and ) to light. The transcripts were induced by blue light only at 30°C suggesting that blue light fails to activate σ at 37°C. The light-induced transcription at 30°C was dependent on a functional blue light sensor, Lmo0799 (which we rename herein as RsbL). A transcriptomic analysis of the response to sub-lethal levels of blue light found that the changes in transcription were almost entirely σ-dependent. A mutant where the light sensing mechanism of RsbL was inactivated through an amino acid substitution (Cys56Ala) was found to have an attenuated response to blue light, but residual activation of σ-dependent genes suggested that alternative routes for activation of σ by light are likely to exist. Overall, the study highlights the central role of σ in the response of this pathogen to visible light and further shows that light sensing is absent at temperatures that exist within the mammalian host.
是一种重要的食源性病原体，对食品保存过程中常用的许多应激条件具有耐受性。在宿主外，该细菌具有腐生生活方式，包括周期性暴露于太阳辐射。已知这种光的蓝色成分会影响应激诱导型σ因子Sigma B（σ）的活性。在本研究中，研究了温度和生长阶段对其对蓝光反应的影响，并使用基于RNAseq的方法阐明了对蓝光的全局转录反应。发现稳定期细胞比指数期细胞对蓝光（470nm）杀伤的抵抗力明显更强。温度对蓝光抗性也有显著影响，在37°C培养的细胞比在30°C生长的细胞更敏感。证实了σ在耐光性中的作用，但仅在30°C时观察到这种效应。通过测量已知的σ依赖性基因（、和）对光的转录反应来评估蓝光对σ的激活。转录本仅在30°C时被蓝光诱导，这表明蓝光在37°C时无法激活σ。30°C时的光诱导转录依赖于功能性蓝光传感器Lmo0799（我们在此将其重新命名为RsbL）。对亚致死水平蓝光反应的转录组分析发现，转录变化几乎完全依赖于σ。通过氨基酸取代（Cys56Ala）使RsbL的光传感机制失活的突变体对蓝光的反应减弱，但σ依赖性基因的残余激活表明可能存在光激活σ的替代途径。总体而言，该研究突出了σ在这种病原体对可见光反应中的核心作用，并进一步表明在哺乳动物宿主体内存在的温度下不存在光传感。
