School of Civil Engineering, Hefei University of Technology, Hefei, 230009, China.
Department of Soil and Water Sciences, China Agricultural University, Beijing, 100193, China.
Ecotoxicol Environ Saf. 2020 May;194:110340. doi: 10.1016/j.ecoenv.2020.110340. Epub 2020 Mar 2.
Flagellar motility enables resource acquisition and noxious substance evasion, underpinning imperative ecological processes in aquatic environments. Yet the underlying mechanism that links flagellar motility with surface attachment and thereby biofilm formation, especially in conditions of limited resource availability, remains elusive. Here, we present experimental and modeling evidence to unveil bacterial motility and biofilm formation under nutrient-limited stresses with Pseudomonas aeruginosa (WT) and its nonflagellated isogenic mutant (ΔfliC) as model bacteria. Results revealed that boosted flagellar motility of WT strain promoted biofilm initialization to a peak value of 0.99 × 10 cells/cm at 1/50 dilution after 20 min incubation. We hypothesized that bacteria can invoke instant motility acceleration for survival confronting nutrient-limited stress, accompanied by optimized chemotactic foraging through sensing ambient chemical gradients. Accordingly, accelerated cell motility in oligotrophic environment created increased cell-cell and cell-surface interactions and thereof facilitated biofilm initialization. It was confirmed by the consistence of modeling predictions and experimental results of cell velocity and surface attachment. With the development of biofilm, promotion effect of flagellar motility responding to nutrient deprivation-stress faded out. Instead, loss of motility profiting increased growth rates and extracellular protein excretion, associated with an enhancement of biofilm development for the mutant in oligotrophic aquatic environment. For both strains, nutrient limitation evidently reduced planktonic cell propagation as expected. Our results offer new insights into the mechanical understanding of biofilm formation shaped by environmental stresses and associating biological responses.
鞭毛运动使水生环境中的资源获取和有害物质规避成为可能，为必要的生态过程提供了支撑。然而，将鞭毛运动与表面附着联系起来，从而形成生物膜的潜在机制仍然难以捉摸。在这里，我们提出了实验和建模证据，以揭示在营养有限的条件下，铜绿假单胞菌（WT）及其无鞭毛的同基因突变体（ΔfliC）作为模型细菌的细菌运动和生物膜形成。结果表明，WT 菌株增强的鞭毛运动促进了生物膜的初始形成，在 20 分钟孵育后，在 1/50 的稀释度下达到峰值 0.99×10^6 个细胞/cm。我们假设，当面临营养有限的压力时，细菌可以通过感应环境化学梯度来进行即时的运动加速，以促进生存。因此，在贫营养环境中加速的细胞运动增加了细胞间和细胞与表面的相互作用，从而促进了生物膜的初始形成。这与细胞速度和表面附着的建模预测和实验结果一致。随着生物膜的发展，鞭毛运动对营养剥夺应激的促进作用逐渐消失。相反，失去运动能力会增加生长速率和细胞外蛋白的排泄，这与突变体在贫营养水生环境中生物膜的发展增强有关。对于这两种菌株，营养限制显然如预期的那样减少了浮游细胞的繁殖。我们的研究结果为环境压力下生物膜形成的机械理解提供了新的见解，并与生物响应有关。
