Project description:Bacteria are known to adhere to surfaces via self-produced extracellular polymeric substances organized as biofilms. In subsurface areas with low oxygen, limited nutrients, and toxic contaminants, biofilms are crucial for microbial survival and persistence. However, the relationship between biofilm formation and survival in such environments is not well-documented. At the Oak Ridge Reservation Field Research Center (ORRFRC), we observed a high abundance of Rhodanobacter species in conditions with elevated nitrate, metals, organics, and nitric acid. This study investigated the role of biofilm formation in their survival and the underlying molecular mechanisms in diverse geochemical niches. We examined sixteen phylogenetically diverse Rhodanobacter strains for biofilm formation under varying nutrient, pH, and nitrate conditions. Our findings indicate that biofilm formation is a strain-specific phenotype, correlating with environmental stresses, especially in low pH and nitrate conditions. Comparative genomic analysis revealed unique traits in the high biofilm-forming FW021-MT20 strain, such as the absence of flagella and chemotaxis genes and the presence of unique secretion system VI genes, as supported by pangenomic results. Additional tests on biofilm formation in response to field-relevant metals highlighted increased biofilm formation under aluminum stress in strains typically exhibiting weaker biofilm capabilities. Further investigation using RB-Tnseq, proteomics, and TEM indicated flagellar loss under aluminum stress, linked to increased cyclic AMP and di-GMP levels. Our results shed light on the adaptive strategies of Rhodanobacter strains in subsurface environments, suggesting genetic factors linked to biofilm formation and metal stress tolerance, thereby enhancing our understanding of microbial survival under environmental stress.
