Role of planktonic and sessile extracellular metabolic byproducts on Pseudomonas aeruginosa and Escherichia coli intra and interspecies relationships

摘要

Bacterial species are found primarily as residentsof complex surface-associated communities, knownas biofilms. Although these structures prevail in nature,bacteria still exist in planktonic lifestyle and differ fromthose in morphology, physiology, and metabolism. Thisstudy aimed to investigate the influence of physiologicalstates of Pseudomonas aeruginosa and Escherichia coli incell-to-cell interactions. Filtered supernatants obtainedunder planktonic and biofilm cultures of each single specieswere supplemented with tryptic soy broth (TSB) andused as the growth media (conditioned media) to planktonicand sessile growth of both single- and two-speciescultures. Planktonic bacterial growth was examinedthrough OD640 measurement. One-day-old biofilms wereevaluated in terms of biofilm biomass (CV), respiratoryactivity (XTT), and CFU number. Conditioned mediaobtained either in biofilm or in planktonic mode of lifetriggered a synergistic effect on planktonic growth, mainlyfor E. coli single cultures growing in P. aeruginosa supernatants.Biofilms grown in the presence of P. aeruginosabiofilms-derived metabolites presented less mass and activity.These events highlight that, when developed in biofilm,P. aeruginosa release signals or metabolites able to prejudicesingle and binary biofilm growth of others speciesand of their own species. However, products released bytheir planktonic counterparts did not impair biofilm growthor activity. E. coli, living as planktonic or sessile cultures,released signals and metabolites or removed un-beneficialcompounds which promoted the growth and activity of allthe species. Our findings revealed that inter and intraspeciesbehaviors depend on the involved bacteria and theiradopted mode of life.