Biofilms aid bacterial adhesion to surfaces via direct and indirect mechanisms, and formation of biofilms is considered as an important strategy for adaptation and survival in sub-optimal environmental conditions. However, the molecular underpinnings of biofilm formation in subsurface sediment/groundwater ecosystems where microorganisms often experience fluctuations in nutrient input, pH, nitrate or metal concentrations is underexplored. We examined biofilm formation under different nutrient, pH, metal, and nitrate regimes of 16 Rhodanobacter strains isolated from subsurface groundwater wells spanning diverse pH (3.5 to 5) and nitrate levels (13.7 to 146 mM). Eight Rhodanobacter strains demonstrated significant biofilm growth under low pH, suggesting adaptation to survive and grow at low pH. Biofilms intensified under aluminum stress, particularly in strains possessing fewer genetic traits associated with biofilm formation warranting further investigation. Through RB-TnSeq, proteomics, use of specific mutants and transmission electron microscopy analysis, we discovered flagellar loss under aluminum stress, indicating a potential relationship between motility, metal tolerance, and biofilm growth. Comparative genomic analyses revealed absence of flagella and chemotaxis genes, and presence of putative Type VI secretion system in the high biofilm-forming strain FW021-MT20. This study identifies genetic determinants associated with biofilm growth in a predominant environmental genus, Rhodanobacter, under metal stress and identifies traits aiding survival and adaptation to contaminated subsurface environments.

中文翻译：

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环境胁迫下红细菌鞭毛损失和生物膜生长的分子机制和环境适应


生物膜通过直接和间接机制帮助细菌粘附到表面，生物膜的形成被认为是在次优环境条件下适应和生存的重要策略。然而，微生物经常经历养分输入、pH、硝酸盐或金属浓度波动的地下沉积物/地下水生态系统中生物膜形成的分子基础尚未得到充分探索。我们检查了从地下地下水井中分离出的 16 种红细菌菌株在不同营养、pH、金属和硝酸盐条件下的生物膜形成，跨越不同的 pH（3.5 至 5）和硝酸盐水平（13.7 至 146 mM）。八种红杆菌属菌株在低 pH 值下表现出显着的生物膜生长，表明其适应在低 pH 值下生存和生长。生物膜在铝胁迫下增强，特别是在与生物膜形成相关的遗传特征较少的菌株中，值得进一步研究。通过 RB-TnSeq、蛋白质组学、特定突变体的使用和透射电子显微镜分析，我们发现铝胁迫下鞭毛损失，表明运动性、金属耐受性和生物膜生长之间的潜在关系。比较基因组分析显示，高生物膜形成菌株 FW021-MT20 不存在鞭毛和趋化基因，并且存在推定的 VI 型分泌系统。这项研究确定了在金属胁迫下与主要环境属红细菌属生物膜生长相关的遗传决定因素，并确定了有助于生存和适应受污染的地下环境的特征。