RAPISARDA Viviana Andrea
congresos y reuniones científicas
High phosphate concentration impairs biofilm formation and stability in Escherichia coli
GRILLO-PUERTAS, M.; RINTOUL, M. R.; RAPISARDA, V. A.
Congreso; VII CONGRESO DE LA SOCIEDAD ARGENTINA DE MICROBIOLOGÍA GENERAL (SAMIGE) Bicentenario; 2011
Biofilm is the prevailing microbial life-style in most natural environments and it often serves as a strategy to overcome stress. The amount and structure of biofilm could be modified by the culture conditions. In several organisms, such as Escherichia coli, Pseudomona aeruginosa, Vibrio cholerae, Klebsiella aerogenes, Salmonella enterica serovar typhimurium, etc., inorganic polyphosphate (polyP) formation was shown to be critical for attributes such as motility, quorum sensing, biofilm formation, resistance to stress, and stationary-phase survival. PolyP is a chain of tens or many hundreds of phosphate residues linked by high-energy phosphoanhydride bonds. The main enzymes associated to polyP metabolism in E. coli are polyphosphate kinase (encoded by ppk) and exopolyphosphatase (ppx). We have previously shown that E. coli cells grown in media containing a critical phosphate concentration >37 mM maintained a high polyP level in stationary phase (up to 96 h) and enhanced the cellular fitness. Moreover, we have observed that the decrease of polyP level in low phosphate media was reversible when phosphate was added at 24 h of culture. The aim of this work was to analyze the effect of phosphate concentrations on E. coli biofilm. The cells were grown in minimal medium containing different phosphate concentrations in polystyrene microtiter plates at 30ºC. Biofilms assay was carried out by the OToole and Kolter method. At 48 h of growth, the biofilm formation in media with 40 mM phosphate (MT+P) was lower in respect to that in media with sufficient phosphate concentration (2 mM, MT). Furthermore, the amount of biofilm determined at 48 h was also decreased by the addition at 24 h of 40 mM phosphate to MT growing cultures. When a ppk ppx mutant was analyzed in the same conditions, opposite results were obtained. The wild type biofilm formation was maximal at 10 mM phosphate and start diminishing at 15 mM, whereas for the mutant a significant biofilm formation was observed from 15 mM. In addition, we analyzed the production of curli, swarming and swimming motility as possible mechanisms related to the observed phenotypes. Similar results were obtained with an environmental isolate of Pseudomonas aeruginosa. According to our results, we assume that internal Pi concentration is an important signal for biofilm formation and stability. This Pi concentration is influenced by the maintenance of polyP levels in stationary phase.