Stress, Phages, and EPS: Factors That Enhance Bradyrhizobium Biofilm Formation
Published Web Location
https://doi.org/10.5070/BS3.69983
Abstract
Biofilms and their exopolysaccharide (EPS) matrix help soil rhizobia ride out stress, colonize roots, and ultimately succeed in symbiosis.
We asked whether bacteriophages and common abiotic stressors modulate EPS-linked biofilm traits in Bradyrhizobium S3.9.2GM. Using a
validated crystal violet (CV) microtiter assay for biomass and Congo Red (CR) colony phenotyping for matrix-linked traits, we found that
phage and sublethal stressors (osmotic, oxidative, temperature shock) generally increased biofilm biomass, with the largest effects under
combined phage + stress conditions. One-way ANOVA showed a strong treatment effect on OD570 (biofilm biomass; p < 0.001), while mucoid
score and CR halo intensity trended upward in combined treatments but were not significant at α = 0.05. These patterns are consistent with
literature showing stress-induced EPS in rhizobia and context-dependent phage–biofilm interactions, and they suggest that simultaneous
biotic and abiotic pressures can amplify EPS-associated phenotypes in the rhizosphere.