Spaceflight-induced changes in polymicrobial biofilm population and structure

Biofilms represent a common mode of bacterial growth, including the water recovery system (WRS) in spacecraft. Several factors have been associated with biofilm structure, including shear forces, microbial community composition, and available nutrients and other culture conditions. During an investigation of biofilm formation of a mixed cystitis isolate, Escherichia coli F11-mCherry and Pseudomonas aeruginosa PAO1- gfp culture during spaceflight in BioCell TM flight hardware with an artificial urine medium, we observed the gas-permeable Teflon (Tf) covering to become heavily colonized after 4 d by a P. aeruginosa -dominated biofilm that took on a structure resembling Van Gogh’s Starry Night. In contrast, Tf-adherent biofilms on the corresponding ground control exhibited no obvious clumping. The underlying stainless steel (SS)-adherent biofilms exhibited no obvious differences in morphology. Biofilm populations on both Tf and SS decreased and the morphology became more uniform at later time points (14 d and 117 d). In most cases, biofilms were more prominent in spaceflight samples than corresponding ground controls. E. coli was observed primarily at the early (4 d) time point, however P. aeruginosa , also associated with cystitis, was predominant at all time points. At 117-d, colonization was greatly reduced to a small number of P. aeruginosa , many of which became elongated on SS. Based on our results and similar findings by other investigators, we propose that microgravity conditions represent a factor that can influence biofilm formation, structure and their bacterial populations.