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.
Project description:Prolific heterotrophic biofilm growth is a common occurrence in airport receiving streams containing deicer and anti-icer runoff. This study investigated relations of heterotrophic biofilm prevalence and community composition to environmental conditions at stream sites upstream and downstream of Milwaukee Mitchell International Airport in Milwaukee, WI, during two deicing seasons (2009–2010 and 2010–2011). Modern genetic tools (such as microarray) have not previously been applied to biofilm communities in this type of setting. We used microarray results to characterize biofilm community composition as well as the response of the biofilm community to environmental factors (i.e., organic content (using chemical oxygen demand concentration) and temperature).
Project description:Environmental cues sometimes have a direct impact on phage particle stability, as well as bacterial physiology and metabolism, having a profound effect on phage infection outcome. Here, we explore the impact of temperature on the interplay between phage Kayvirus rodi (phiIPLA-RODI) and its host, Staphylococcus aureus. Our results show that phiIPLA-RODI is a more effective predator at room (25 °C) compared to body temperature (37 °C) against planktonic cultures of several strains with varying degrees of phage susceptibility. This result differs from most known examples of temperature-dependent phage infection, in which optimum infection is correlated with the host growth rate. Further characterization of this phenomenon was carried out with strains IPLA15 and IPLA16, whose respective MICs were 7 log units and a 1-log unit higher at 37 °C than at 25 °C. Our results demonstrated that the phage also had a greater impact at room temperature during biofilm development and for the treatment of preformed biofilms. There was no difference in phage adsorption between the two temperatures for strain IPLA16. Conversely, adsorption of phiIPLA-RODI to IPLA15 was reduced at 37 °C compared to 25 °C. Moreover, confocal microscopy analysis indicated that the biofilm matrix of both strains has a greater content of PIA/PNAG at 37 °C than at 25 °C. Regarding infection parameters, we observed longer duration of the lytic cycle at 25 °C for both strains, and infection of IPLA15 by phiIPLA-RODI resulted in a smaller burst size at 37 °C than at 25 °C. Finally, we also found that the rate of phage resistant mutant selection was higher at 37 °C for both strains. Altogether, this information highlights the impact that bacterial responses to environmental factors have on phage-host interactions. Moreover, phage phiIPLA-RODI appears to be a highly effective candidate for biofilm disinfection at room temperature, while its efficacy in biofilm-related infections will require combination with other antimicrobials.