Abstract：
Microbial community adaptability to pH stress plays a crucial role in biofilm formation. This study aims to investigate the regulatory mechanisms of exogenous putrescine on pH stress, as well as enhance understanding and application for the technical measures and molecular mechanisms of biofilm regulation. Findings demonstrated that exogenous putrescine acted as a switch-like distributor affecting microorganism pH stress, thus promoting biofilm formation under acid conditions while inhibiting it under alkaline conditions. As pH decreases, the protonation degree of putrescine increases, making putrescine more readily adsorbed. Protonated exogenous putrescine could increase cell membrane permeability, facilitating its entry into the cell. Subsequently, putrescine consumed intracellular H+ by enhancing the glutamate-based acid resistance strategy and the γ-aminobutyric acid metabolic pathway to reduce acid stress on cells. Furthermore, putrescine stimulated ATPase expression, allowing for better utilization of energy in H+ transmembrane transport and enhancing oxidative phosphorylation activity. However, putrescine protonation was limited under alkaline conditions, and the intracellular H+ consumption further exacerbated alkali stress and inhibits cellular metabolic activity. Exogenous putrescine promoted the proportion of fungi and acidophilic bacteria under acidic stress and alkaliphilic bacteria under alkali stress while having a limited impact on fungi in alkaline biofilms. Increasing Bdellovibrio under alkali conditions with putrescine further aggravated the biofilm decomposition. This research shed light on the unclear relationship between exogenous putrescine, environmental pH, and pH stress adaptability of biofilm. By judiciously employing putrescine, biofilm formation could be controlled to meet the needs of engineering applications with different characteristics.IMPORTANCEThe objective of this study is to unravel the regulatory mechanism by which exogenous putrescine influences biofilm pH stress adaptability and understand the role of environmental pH in this intricate process. Our findings revealed that exogenous putrescine functioned as a switch-like distributor affecting the pH stress adaptability of biofilm-based activated sludge, which promoted energy utilization for growth and reproduction processes under acidic conditions while limiting biofilm development to conserve energy under alkaline conditions. This study not only clarified the previously ambiguous relationship between exogenous putrescine, environmental pH, and biofilm pH stress adaptability but also offered fresh insights into enhancing biofilm stability within extreme environments. Through the modulation of energy utilization, exerting control over biofilm growth and achieving more effective engineering goals could be possible.
摘要：
微生物群落对pH胁迫的适应性在生物膜形成中起着至关重要的作用。本研究旨在探讨外源腐胺对pH值胁迫的调控机制,以及增强对生物膜调控的技术措施和分子机制的理解和应用。研究结果表明，外源腐胺充当开关样分配器，影响微生物pH值胁迫，从而在酸性条件下促进生物膜的形成，而在碱性条件下抑制生物膜的形成。随着pH值的降低,腐胺的质子化程度增加，使腐胺更容易吸附。质子化外源腐胺能增加细胞膜通透性,促进其进入细胞。随后，腐胺通过增强基于谷氨酸的酸抗性策略和γ-氨基丁酸代谢途径来消耗细胞内的H+，以减少对细胞的酸应激。此外，腐胺刺激ATP酶表达，允许在H跨膜转运中更好地利用能量并增强氧化磷酸化活性。然而,腐胺质子化在碱性条件下受到限制，细胞内H+的消耗进一步加剧了碱胁迫并抑制了细胞代谢活性。外源腐胺促进了酸性胁迫下真菌和嗜酸菌的比例和碱胁迫下嗜碱性细菌的比例，但对碱性生物膜中真菌的影响有限。在碱性条件下用腐胺增加Bdellovibrio进一步加剧了生物膜的分解。这项研究揭示了外源腐胺之间不清楚的关系，环境pH值,和生物膜的pH胁迫适应性。通过明智地使用腐胺，可以控制生物膜的形成，以满足具有不同特性的工程应用需求。重要意义本研究的目的是阐明外源腐胺影响生物膜pH胁迫适应性的调节机制，并了解环境pH在这一复杂过程中的作用。我们的发现表明，外源腐胺充当开关样分配器，影响基于生物膜的活性污泥的pH应力适应性，这促进了酸性条件下生长和繁殖过程的能量利用，同时限制了碱性条件下生物膜的发育以节省能量。这项研究不仅阐明了外源性腐胺之间先前的模糊关系，环境pH值,和生物膜pH值胁迫适应性，但也为增强极端环境中的生物膜稳定性提供了新的见解。通过能量利用的调制,对生物膜生长施加控制并实现更有效的工程目标是可能的。
