Bacterial biofilm development in response to toxic molecules

大多数细菌生长在称为生物膜的表面相关群落中，这种生长模式可以保护它们免受捕食者和有毒物质的伤害，包括洗涤剂、抗生素和有毒金属。尽管生物膜在环境、农业和动物/人类福祉中发挥着关键作用，但调节生物膜发育的信号和途径对化学物质暴露的反应知之甚少。我们以前已经证明，细菌暴露在亚致死浓度的各种抗菌剂、洗涤剂和消毒剂中会刺激生物被膜的形成。对于某些化合物，生物膜刺激发生的浓度远远低于影响生长的浓度，这表明细菌检测到微量的潜在危险分子，并以增加生物膜的形成作为回应。我们认为，生物膜形成的增加是一种快速的保护性反应，以减轻对种群的损害。这种非特异性反应让人想起高等生物体的先天免疫反应，可能会赢得时间，从而使种群随后能够发展出更经典的抗药性形式。基于初步研究，我们的工作假设是，暴露于亚MIC抗生素、洗涤剂或消毒剂会导致细胞损伤，从而触发应激反应，增加修复这种损伤的代谢需求。目前还不清楚这些反应如何与生物被膜水平的增加有关。我们将比较两个模式物种，铜绿假单胞菌和大肠杆菌，我们对它们有丰富的工具，以得出关于生物被膜刺激的更普遍的结论。在之前由NSERC资助的研究中，我们发现了在接触各种抗菌剂时未能增加生物被膜形成的突变株。每个物种都产生了一个有趣的突变的简短名单，我们将进一步描述这些突变，以了解它们如何以及为什么没有对这些化学线索做出反应。我们的数据表明，亚MIC抗生素会造成损害，其修复会增加能量(ATP)需求，从而增加呼吸。我们将确定这些增加代谢能力的需求如何与更多生物膜的生产联系在一起，这需要增加基质成分的合成。我们的具体目标是：1)表征铜绿假单胞菌和大肠杆菌野生型和呼吸突变株在存在替代电子受体的情况下对亚MIC抗生素的生物膜刺激反应；2)研究有氧中枢代谢、环二GMP水平和生物膜基质多糖成分产生之间的联系这项工作将提供对生物膜生物学以及细菌感知和响应生物活性小分子的方式的新理解。在许多情况下，增加生物膜的形成是可取的--例如，废水处理、从尾矿中提取低浓度矿物，或者为了促进生长而在植物根上定居--我们的工作可能为如何更容易地实现这一目标提供线索。

Most bacteria grow in surface-associated communities called biofilms, a mode of growth that protects them from predators and noxious substances, including detergents, antibiotics, and toxic metals. The signals and pathways that modulate biofilm development in response to chemical exposure are poorly understood, even though biofilms play key roles in the environment, agriculture, and animal/human well-being. We showed previously that exposure of bacteria to sublethal concentrations of diverse antimicrobials, detergents, and disinfectants stimulates biofilm formation. For some compounds, biofilm stimulation occurred at concentrations far below those that impacted growth, suggesting that bacteria detect minute amounts of potentially dangerous molecules and respond with increased biofilm formation. We propose that increases in biofilm formation are a rapid protective response to mitigate damage to the population. This non-specific response is reminiscent of the innate immune responses of higher organisms, and likely buys time so the population can subsequently develop more classical forms of resistance. Based on preliminary studies, our working hypothesis is that exposure to sub-MIC antibiotics, detergents, or disinfectants causes cellular damage that triggers stress responses, increasing metabolic demand to repair this damage. It is not yet clear how these responses are linked to increased levels of biofilm. We will compare two model species, P. aeruginosa and Escherichia coli for which we have a wealth of tools, to make more generalized conclusions about biofilm stimulation. In prior NSERC-funded studies, we identified mutants that failed to increase biofilm formation when exposed to various antimicrobials. Each species yielded a short list of interesting mutants that we will further characterize to understand how and why they fail to respond to these chemical cues. Our data suggest that sub-MIC antibiotics cause damage whose repair increases energy (ATP) demand and thus respiration. We will determine how these demands for increased metabolic capacity are linked to production of more biofilm, which requires increased synthesis of matrix components. Our specific aims are to: 1) Characterize the biofilm stimulation responses of P. aeruginosa and E. coli wild type and respiratory mutants when exposed to sub-MIC antibiotics in the presence of alternative electron acceptors 2) Investigate the links between aerobic central metabolism, cyclic-di-GMP levels, and production of biofilm matrix polysaccharide components This work will provide new understanding of biofilm biology and the ways in which bacteria perceive and respond to bioactive small molecules. There are many scenarios where increased biofilm formation is desirable - for example, wastewater treatment, extraction of low-concentration minerals from mine tailings, or plant root colonization for growth promotion - and our work may provide clues on how to more easily achieve this goal.