PhoB activation in non-limiting phosphate condition by the maintenance of high polyphosphate levels in the stationary phase inhibits biofilm formation in Escherichia coli

Abstract

Polyphosphate (polyP) degradation in Escherichia coli stationary phase triggers biofilm formation via the LuxS quorum sensing system. In media containing excess of phosphate (Pi), high polyP levels are maintained in the stationary phase with the consequent inhibition of biofilm formation. The transcriptional-response regulator PhoB, which is activated under Pi limitation, is involved in the inhibition of biofilm formation in several bacterial species. In the current study, we report, for the first time, we believe that E. coli PhoB can be activated in non-limiting Pi conditions, leading to inhibition of biofilm formation. In fact, PhoB was activated when high polyP levels were maintained in the stationary phase, whereas it remained inactive when the polymer was degraded or absent. PhoB activation was mediated by acetyl phosphate with the consequent repression of biofilm formation owing to the downregulation of c-di-GMP synthesis and the inhibition of autoinducer-2 production. These results allowed us to propose a model showing that PhoB is a component in the signal cascade regulating biofilm formation triggered by fluctuations of polyP levels in E. coli cells during stationary phase.

Intracellular Polyphosphate Levels in <i>Gluconacetobacter diazotrophicus</i> Affect Tolerance to Abiotic Stressors and Biofilm Formation

“…Collectively, these data demonstrated that PAL5 copper tolerance correlated with the degradation of preformed polyP. In agreement with these results, polyP degradation was identified as a step in an alternative mechanism to detoxify metals in E. coli (13), acidophilic bacteria (1), and archaea (31). Further studies are needed to elucidate other key factors involved in the polyP-dependent metal detoxification system in G. diazotrophicus .…”

“…Polyphosphate (polyP) is a linear polymer of inorganic phosphate (Pi) residues linked by phosphoanhydride bonds and is present in bacteria, archaea, fungi, protozoa, plants, and animals (19). PolyP is involved in physiological and regulatory mechanisms, including motility, competence, biofilm formation, and virulence, in several bacteria and parasites (10, 12, 13, 21, 29). It also plays roles in bacterial survival in the stationary phase and responses to nutrient starvation and other stress conditions (7, 11, 29, 32).…”

Control of the phoBR Regulon in Escherichia coli

“…PolyP may also influence expression of the Pho regulon during the stationary phase (161). Grillo-Puertas et al showed that during the stationary phase PhoB could be activated when cells were grown in a medium containing high levels of phosphate (∼40 mM P i ) (161). It was demonstrated that this activation depended upon the production of acetyl phosphate and the production of polyP.…”

Molecular Mechanisms of Phosphate Homeostasis in <i>Escherichia coli</i>

“…PolyP is also involved in cell signaling, respiratory chain gene expression, bacterial persistence, and in stress response networks [93][94][95][96]. It has recently been shown that when external Pi levels are very high, polyP can even activate PhoB during the stati o n a r yp h a s eo fg r o w t ht h r o u g ht h es m a l l molecule acetyl phosphate [97]. It is then postulated that phospho-PhoB inhibits the synthesis of c-di-GMP, blocking the production of AI-2, leading to the inhibition of biofilm formation.…”