Bacterial biofilm development in response to toxic molecules

大多数细菌生长在被称为生物膜的表面相关群落中，这种生长方式保护它们免受捕食者和有害物质的侵害，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，但人们对化学暴露下调节生物膜发育的信号和途径知之甚少。我们先前表明，细菌暴露于亚致死浓度的各种抗菌剂、洗涤剂和消毒剂会刺激生物膜的形成。对于一些化合物，生物膜刺激发生在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出反应。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了高等生物的先天免疫反应，并可能为种群随后发展出更经典的抵抗形式赢得了时间。根据初步研究，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，从而引发应激反应，增加修复这种损伤的代谢需求。目前尚不清楚这些反应与生物膜水平的增加有何联系。我们将比较两种模式物种，铜绿假单胞菌和大肠杆菌，我们有丰富的工具，对生物膜刺激作出更广义的结论。在之前nserc资助的研究中，我们发现当暴露于各种抗菌剂时，突变体不能增加生物膜的形成。每个物种都产生了一些有趣的突变体，我们将进一步描述它们的特征，以了解它们如何以及为什么对这些化学线索没有反应。我们的数据表明，亚mic抗生素引起损伤，其修复增加了能量（ATP）需求，从而增加了呼吸。我们将确定这些对增加代谢能力的需求如何与更多生物膜的生产联系起来，这需要增加基质成分的合成。我们的具体目标是：1)表征P. aeruginosa、E. coli野生型和呼吸突变体在暴露于亚mic抗生素和替代电子受体存在时的生物膜刺激反应2)研究有氧中枢代谢、循环二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为生物膜生物学和细菌感知和响应生物活性小分子的方式提供新的认识。在许多情况下，需要增加生物膜的形成-例如，废水处理，从矿山尾矿中提取低浓度矿物质，或植物根定植以促进生长-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.