Probing biofilm development, stress response and heterogeneity-spectroscopic characterization of single and...

Environmental bacterial biofilms play many roles in the ecosystem including cycling of nutrients and serving as food for grazing organisms. Their function is linked to their microbial and chemical composition that may be altered by several parameters including environmental stressors. This manuscript presents a well-characterized model system of four bacterial isolates from a small Swedish river: Pseudomonas sp., Sphingomonas sp., Rhizobium sp. and Pararhizobium sp. Microbiological and chemical phenotypes were investigated including cell and biofilm morphology, as well as biochemical composition in absence and presence of the drug trimethoprim. Vibrational spectroscopy, cryo-X-ray photoelectron spectroscopy and confocal optical microscopy were applied to investigate and characterize monocultures and cocultures. The chemical characterization showed variation of the energy storage substance polyhydroxyalkanoates as well as polysaccharides between isolates and drug exposures. Spatial heterogeneities were observed using Raman microspectroscopy where Sphingomonas sp. cells, formed small clusters, inside the four species consortium, an organization that appeared to protect this isolate during exposure to trimethoprim.