Molecular mechanisms and environmental adaptations of flagellar loss and biofilm growth of Rhodanobacter under environmental stress

This project 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.

本研究针对16株分离自地下地下水井的红杆菌属（Rhodanobacter）菌株展开探究，分析其在不同营养条件、pH值、金属及硝酸盐环境下的生物膜形成能力；这些菌株的来源环境pH范围为3.5至5，硝酸盐浓度跨度为13.7至146 mM。其中8株红杆菌在低pH环境下表现出显著的生物膜生长能力，提示其具备在低pH条件下存活与增殖的适应性。铝胁迫会促进生物膜形成，该现象在携带较少生物膜形成相关遗传特征的菌株中尤为明显，值得进一步研究。通过RB-TnSeq技术、蛋白质组学分析、特异性突变体实验以及透射电子显微镜观察，本研究发现铝胁迫下菌株会出现鞭毛缺失现象，这提示运动性、金属耐受性与生物膜生长之间存在潜在关联。比较基因组分析结果显示，高生物膜形成能力菌株FW021-MT20缺失鞭毛及趋化相关基因，但含有推定的VI型分泌系统（Type VI secretion system）。本研究明确了环境优势属红杆菌属在金属胁迫下与生物膜生长相关的遗传决定因子，并鉴定出有助于其在受污染地下环境中存活与适应的特征。