Dawoud Turki M, Khatiwara Anita, Park Si Hong, Davis Morgan L, Baker Christopher A, Ricke Steven C, Kwon Young Min
Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, 72701, USA.
Food & Drug Administration/Center for Food Safety and Applied Nutrition, College Park, MD, USA.
Curr Microbiol. 2017 Feb;74(2):257-267. doi: 10.1007/s00284-016-1170-1. Epub 2016 Dec 21.
Contamination of food products by pathogenic microorganisms continues to be a major public health and food industry concern. Non-typhoidal Salmonella species have led to numerous outbreaks associated with various foods. A wide variety of methods have been applied and introduced for treatment of fresh foods to eliminate pathogenic as well as spoilage microorganisms. Salmonella can become exposed to elevated temperatures while associated with hosts such as poultry. In addition, heat treatment is also applied at various stages of processing to retain the shelf life of food products. Despite this, these microorganisms may overcome exposure to such treatments through the efficient expression of stress response mechanisms and result in illness following consumption. Thermal stress induces a range of destructive exposures to bacterial cells such as protein damage and DNA damage caused by reactive oxygen species. In this study, we chose three genes (∆recD, ∆STM14_5307, and ∆aroD) associated with conditionally essential genes required for different aspects of optimal growth at 42 °C and evaluated the responses of wild type and mutant Salmonella Typhimurium strains to uncover potential mechanisms that may enable survival and resistance under thermal stress. The RecBCD complex that initiates repair of double-stranded DNA breaks through homologous recombination. STM14_5307 is a transcriptional regulator involved in stationary phase growth and inositol metabolism. The gene aroD is involved in metabolism and stationary phase growth. These strains were characterized via high throughput phenotypic profiling in response to two different growth temperatures (37 °C (human host temperature) and 42 °C (poultry host temperature)). The ∆aroD strain exhibited the highest sensitivity to the various temperatures followed by the ∆recD and ∆STM14_5307 strains, respectively. Achieving more understanding of the molecular mechanisms of heat survival may lead to the development of more effective strategies to limit Salmonella in food products through thermal treatment by developing interventions that specifically target the pathways these genes are involved in.
致病性微生物对食品的污染仍然是公共卫生和食品行业的一大担忧。非伤寒沙门氏菌已导致多起与各类食品相关的疫情爆发。人们已经应用并引入了各种各样的方法来处理新鲜食品，以消除致病微生物和腐败微生物。沙门氏菌在与家禽等宿主相关联时可能会暴露于高温环境。此外，在食品加工的各个阶段也会进行热处理以延长食品的保质期。尽管如此，这些微生物可能会通过高效表达应激反应机制来克服此类处理，从而在食用后导致疾病。热应激会对细菌细胞造成一系列破坏性影响，如活性氧导致的蛋白质损伤和DNA损伤。在本研究中，我们选择了三个与在42℃下最佳生长的不同方面所需的条件必需基因相关的基因（∆recD、∆STM14_5307和∆aroD），并评估野生型和突变型鼠伤寒沙门氏菌菌株的反应，以揭示在热应激下可能实现存活和抗性的潜在机制。RecBCD复合物通过同源重组启动双链DNA断裂的修复。STM14_5307是一种参与稳定期生长和肌醇代谢的转录调节因子。aroD基因参与代谢和稳定期生长。通过对两种不同生长温度（37℃（人体宿主温度）和42℃（家禽宿主温度））的高通量表型分析对这些菌株进行了表征。∆aroD菌株对各种温度表现出最高的敏感性，其次分别是∆recD和∆STM14_5307菌株。对热存活分子机制有更多了解，可能会通过开发专门针对这些基因所涉及途径的干预措施，制定更有效的策略，通过热处理来限制食品中的沙门氏菌。
