PDF(Pubmed)
Abstract：
High salinity inhibits microbial activity in the bioremediation of saline wastewater. To alleviate osmotic stress, glycine betaine (GB), an osmoprotectant, is added to enhance the secretion of extracellular polymeric substances (EPS). These EPS are pivotal in withstanding environmental stressors, yet the intricate interplay between GB supplementation and microbial responses through EPS modifications-encompassing composition, molecular architecture, and electrochemical features-remains elusive in hypersaline conditions. Here we show microbial strategies for salinity endurance by investigating the impact of GB on the dynamic alterations of EPS properties. Our findings reveal that GB supplementation at 3.5% salinity elevates the total EPS (T-EPS) content from 12.50 ± 0.05 to 24.58 ± 0.96 mg per g dry cell weight. The observed shift in zeta potential from -28.95 to -6.25 mV at 0% and 3.5% salinity, respectively, with GB treatment, indicates a reduction in electrostatic repulsion and compaction. Notably, the EPS protein secondary structure transition from β-sheet to α-helix, with GB addition, signifies a more compact protein configuration, less susceptible to salinity fluctuations. Electrochemical analyses, including cyclic voltammetry (CV) and differential pulse voltammetry (DPV), reveal GB\'s role in promoting the release of exogenous electron shuttles, such as flavins and c-type cytochromes (c-Cyts). The enhancement in DPV peak areas (QDPV) with GB addition implies an increase in available extracellular electron transfer sites. This investigation advances our comprehension of microbial adaptation mechanisms to salinity through EPS modifications facilitated by GB in saline habitats.
摘要：
高盐度抑制含盐废水生物修复中的微生物活性。为了缓解渗透压力，甘氨酸甜菜碱（GB），一种渗透保护剂,添加以增强胞外聚合物（EPS）的分泌。这些每股收益在承受环境压力方面至关重要，然而，通过包含EPS修饰的组合物，GB补充剂和微生物反应之间的复杂相互作用，分子结构,和电化学特征-在高盐条件下仍然难以捉摸。在这里，我们通过研究GB对EPS特性动态变化的影响，展示了盐度耐久性的微生物策略。我们的发现表明，在盐度为3.5％时补充GB可将总EPS（T-EPS）含量从每克干细胞重量的12.50±0.05提高到24.58±0.96mg。在0％和3.5％盐度下观察到的ζ电位从-28.95到-6.25mV的变化，分别,用GB处理，表示静电排斥和压实的减少。值得注意的是,EPS蛋白二级结构从β-折叠转变为α-螺旋,加上GB，意味着更紧凑的蛋白质结构，不太容易受到盐度波动的影响。电化学分析,包括循环伏安法（CV）和差分脉冲伏安法（DPV），揭示GB在促进外源电子穿梭释放中的作用，例如黄素和c型细胞色素(c-Cyts)。添加GB时DPV峰面积（QDPV）的增强意味着可用的细胞外电子转移位点的增加。这项研究通过GB在盐渍生境中促进的EPS修饰，提高了我们对微生物对盐度的适应机制的理解。
