Related Experiment Videos
Effect of divalent cations on permeabilizer-induced lysozyme lysis of Pseudomonas aeruginosa
H M Ayres1, J R Furr, A D Russell
1Welsh School of Pharmacy, Cardiff University, UK.
Abstract:
The presence of divalent (Mg2+) ions greatly reduced the lysis of Pseudomonas aeruginosa strain G48 in a system at pH 7.8 or 9.0 consisting of ethylenediamine tetraacetic acid (EDTA), lysozyme and tris. Similar reductions in lysis occurred when EDTA was replaced by nitrilotriacetic acid, sodium citrate or sodium polyphosphate. The effect depended on the cation concentration. Mg2+ may replace cations removed from the outer membrane, or may effectively remove the permeabilizer from the system. The results suggest that the permeabilizing activity associated with these agents against this organism has a common basis in affecting the outer membrane.
Insights
Magnesium ions (Mg2+) significantly inhibit the breakdown of Pseudomonas aeruginosa outer membranes. This effect, observed with agents like ethylenediamine tetraacetic acid (EDTA), suggests a common mechanism impacting membrane integrity.
Area of Science:
- Microbiology
- Biochemistry
- Molecular Biology
Background:
- Pseudomonas aeruginosa possesses a robust outer membrane providing resistance to environmental stresses and antimicrobial agents.
- Ethylenediamine tetraacetic acid (EDTA) and lysozyme are known to permeabilize the bacterial outer membrane by chelating divalent cations and degrading peptidoglycan, respectively.
- The precise mechanisms by which these agents affect outer membrane integrity, particularly in the presence of other ions, require further elucidation.
Purpose of the Study:
- To investigate the influence of divalent magnesium ions (Mg2+) on the lysis of Pseudomonas aeruginosa strain G48 induced by ethylenediamine tetraacetic acid (EDTA), lysozyme, and tris buffer.
- To determine if other chelating agents exhibit similar effects to EDTA in the presence of Mg2+.
- To explore the potential mechanisms by which Mg2+ modulates the permeabilizing activity of these agents on the bacterial outer membrane.
Main Methods:
- Bacterial lysis assays were performed on Pseudomonas aeruginosa strain G48 under alkaline conditions (pH 7.8 and 9.0).
- The system included ethylenediamine tetraacetic acid (EDTA), lysozyme, and tris buffer, with varying concentrations of magnesium ions (Mg2+).
- EDTA was substituted with alternative chelating agents, including nitrilotriacetic acid, sodium citrate, and sodium polyphosphate, to assess comparative effects.
Main Results:
- The addition of divalent magnesium ions (Mg2+) significantly reduced the rate and extent of Pseudomonas aeruginosa lysis in the tested system.
- Similar inhibitory effects on lysis were observed when EDTA was replaced by nitrilotriacetic acid, sodium citrate, or sodium polyphosphate, indicating a general cation effect.
- The observed reduction in lysis was dependent on the concentration of Mg2+ ions present in the system.
- Mg2+ ions may counteract the permeabilizing effects by either re-establishing cation bridges in the outer membrane or by interacting with the permeabilizing agents.
Conclusions:
- Divalent magnesium ions (Mg2+) play a crucial role in stabilizing the outer membrane of Pseudomonas aeruginosa against lysis induced by common permeabilizing agents.
- The inhibitory effect of Mg2+ is concentration-dependent and suggests a common mechanism of action involving the outer membrane structure.
- These findings imply that the permeabilizing activity of agents like EDTA, lysozyme, and similar compounds against this bacterium may share a common basis in their interaction with the bacterial outer membrane.