Related Experiment Videos
Lactic acid permeabilizes gram-negative bacteria by disrupting the outer membrane
H L Alakomi1, E Skyttä, M Saarela
1VTT Biotechnology, FIN-02044 VTT, Espoo, Finland.
Applied and Environmental Microbiology
|May 2, 2000
Summary
Lactic acid permeabilizes the outer membrane of Gram-negative bacteria like E. coli and Salmonella. It also enhances the effectiveness of other antimicrobial agents.
Area of Science:
- Microbiology
- Bacterial Physiology
- Antimicrobial Agents
Background:
- Gram-negative bacteria possess a robust outer membrane that limits the entry of antimicrobial compounds.
- Understanding factors that disrupt outer membrane integrity is crucial for developing effective treatments against bacterial infections.
Purpose of the Study:
- To investigate the effect of lactic acid on the outer membrane permeability of key Gram-negative pathogens.
- To determine if lactic acid acts as a potentiator for other antimicrobial substances.
Main Methods:
- Fluorescent-probe uptake assays were used to measure outer membrane permeability.
- Sensitization to bacteriolysis assays were performed using agents like sodium dodecyl sulfate (SDS) and Triton X-100.
- Lipopolysaccharide (LPS) liberation was analyzed using electrophoresis and fatty acid analysis.
Main Results:
- Lactic acid (5 mM, pH 4.0) significantly increased outer membrane permeability in Escherichia coli O157:H7, Pseudomonas aeruginosa, and Salmonella enterica serovar Typhimurium.
- Lactic acid demonstrated a stronger permeabilization effect than EDTA or hydrochloric acid (HCl).
- Lactic acid sensitized bacteria to lysis by SDS and Triton X-100, and to lysozyme, indicating potentiation of antimicrobial effects.
Conclusions:
- Lactic acid disrupts the outer membrane permeability of Gram-negative bacteria.
- Beyond its pH-lowering effect, lactic acid acts as a permeabilizer and potentiates other antimicrobial agents.