Elucidating the mechanisms and factors influencing biofilm formation in foods

该提交材料要求继续支持生物膜抗菌剂耐药性研究。细菌生物膜在表面上发展，在那里它们变得比在液体悬浮液中生长的对应细菌对抗菌剂和其他应激源更具抗性。 因此，生物膜往往在食品加工厂的抗微生物处理和卫生制度下存活，在那里它们迅速再生并导致下游食品质量损失、产品保质期缩短或食源性疾病。抗微生物治疗后生物膜存活的机制尚不完全清楚;因此，有效的生物膜控制策略仍然是具有社会和经济重要性的目标。我的研究计划的核心重点是阐明生物膜的结构和代谢反应途径，有助于增强抗微生物剂的耐药性，如苯扎氯铵，氯己定和三氯生，使用野生型和突变株沙门氏菌肠道，大肠杆菌O 157，和定义的共培养系统。据推测，先前的压力事件（在低温下生长）和形成的保护性微生态在共培养生物膜，都诱导应激反应途径，导致增强的阻力。 将使用共聚焦激光显微镜（CLM）和全细胞蛋白表达模式对预应力（适应）和未适应生物膜进行比较研究，以记录效果。荧光探针和CLM将在处理和未处理的生物膜中提供关于生物膜细胞状况的原位物理和代谢信息，而蛋白质分析将揭示对抗菌剂的适应以及生物膜内的位置如何影响生物膜代谢过程。“先前生物膜应激”的总体效果将通过使生物膜和重悬的生物膜细菌经受一组施加的应激（例如，抗微生物剂和热）并确定它们各自的存活率。这项研究还将采用相关的显微镜方法（同步辐射软X射线透射显微镜，原子力显微镜，共聚焦显微镜）来检查表面上的细菌-抗菌剂相互作用，以及食品级纳米材料对细菌的影响。

This submission requests continued support for the study of biofilm antimicrobial resistance. Bacterial biofilms develop on surfaces where they become more resistant to antimicrobial agents and other stressors than their counterpart bacteria grown in liquid suspension. Biofilms thus tend to survive antimicrobial treatment and sanitation regimes in food processing plants, where they rapidly regrow and contribute to downstream losses in food quality, reduced product shelf life, or food borne disease. The mechanisms responsible for biofilm survival following antimicrobial treatment are not entirely clear; consequently, effective biofilm control strategies remain a goal of social and economic importance. The core of my research program focuses on elucidating structural and metabolic response pathways of biofilms that contribute to enhanced resistance to antimicrobial agents such as benzalkonium chloride, chlorhexidine and triclosan, using wild-type and mutant strains of Salmonella enterica, Escherichia coli O157, and defined co-culture systems. It is hypothesized that prior stress events (growth at low temperature) and formation of protective microniches in co-culture biofilms, both induce stress response pathways that lead to enhanced resistance. Comparative studies of pre-stressed (adapted) and unadapted biofilms will be performed using confocal laser microscopy (CLM) and whole cell protein expression patterns to document effects. Fluorescent probes and CLM will provide in situ physical and metabolic information on biofilm cell condition in treated and untreated biofilms, whereas protein analyses will reveal how adaptation to antimicrobial agents, as well as location within the biofilm, affect biofilm metabolic processes. The overall effect of 'prior biofilm stress' will be evaluated by subjecting biofilms and resuspended biofilm bacteria to a panel of imposed stresses (e.g., antimicrobial agents and heat) and determining their respective survival. This research will also employ correlative microscopy approaches (synchrotron soft x-ray transmission microscopy, atomic force microscopy, confocal microscopy) to examine bacterial-antimicrobial interactions on surfaces, as well as the effects of food-grade nanomaterials on bacteria.