Antibiotic treatment of Pseudomonas aeruginosa biofilms stimulates expression of the magnesium transporter gene mgtE

Abstract

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen with the capacity to cause serious disease, including chronic biofilm infections in the lungs of cystic fibrosis (CF) patients. These infections are treated with high concentrations of antibiotics. Virulence modulation is an important tool utilized by P. aeruginosa to propagate infection and biofilm formation in the CF airway. Many different virulence modulatory pathways and proteins have been identified, including the magnesium transporter protein MgtE. We have recently found that isogenic deletion of mgtE leads to increased cytotoxicity through effects on the type III secretion system. To explore the role of the CF lung environment in MgtE activity, we investigated mgtE transcriptional regulation following antibiotic treatment. Utilizing quantitative real-time-PCR, we have demonstrated an increase in mgtE transcript levels following antibiotic treatment with most of the 12 antibiotics tested. To begin to determine the regulatory network governing mgtE expression, we screened a transposon-mutant library of P. aeruginosa to look for mutants with potentially altered mgtE activity, using cytotoxicity as a readout. In this screen, we observed that AlgR, which regulates production of the biofilm polysaccharide alginate, alters MgtE-mediated cytotoxicity. This cross-talk between MgtE and AlgR suggests that AlgR is involved in linking external inducing signals (e.g. antibiotics) to mgtE transcription and downstream virulence and biofilm activities. Analysing such interactions may lead to a better understanding of how the CF lung environment shapes P. aeruginosa biofilm infections.

Pseudomonas aeruginosa Magnesium Transporter MgtE Inhibits Type III Secretion System Gene Expression by Stimulating rsmYZ Transcription

“…S1A in the supplemental material). This increase is concordant with transcript levels seen in physiologically relevant concentrations of antibiotics and magnesium (29,30). Similar results were obtained with P. aeruginosa strain PA14 (Fig.…”

“…We also demonstrate that mgtE acts exclusively through the RsmA/RsmY/RsmZ signaling pathway to inhibit ExsAmediated T3SS gene transcription. Because mgtE transcription is significantly upregulated by growth under low-Mg 2ϩ conditions and in the presence of some antibiotics (29,30), this pathway may provide a mechanism for P. aeruginosa to modulate T3SS gene expression in response to signals encountered during infections.…”

Acidosis Potentiates the Host Proinflammatory Interleukin-1β Response to Pseudomonas aeruginosa Infection

“…Subsequently, the cultures were incubated in a 12-well plate for 2.5 h at 37°C and 5% CO 2 . Following incubation, the cultures were resuspended in 1 ml of Z buffer, and the Miller assay was performed as previously described (45). Expression of lacZ was determined by the Miller unit equation (46).…”

Pseudomonas aeuroginosa Biofilm and Antimicrobial Resistance

“…In addition, there are rather complex interactions between biofilm and antibiotics resistance, some antibiotics can induce biofilm formation at the sub minimal concentration (sub-MIC) as signaling molecules [31][32][33]. Thus, the widespread use of β-lactam antibiotics can expose bacteria with low levels f antibiotic concentrations.…”