EFFECT OF INORGANIC CATIONS ON BACTERICIDAL ACTIVITY OF ANIONIC SURFACTANTS

Area of Science:

• Microbiology
• Biochemistry
• Surface Chemistry

Background:

• Anionic surfactants are widely used for their cleaning and antimicrobial properties.
• The interaction between surfactants, cell surfaces, and environmental ions is complex.
• Understanding factors influencing surfactant efficacy is crucial for developing effective antimicrobial agents.

Purpose of the Study:

• To investigate the effect of inorganic cations on the bactericidal activity of anionic surfactants.
• To elucidate the mechanism by which cations influence surfactant effectiveness against bacteria.

Main Methods:

• Testing the bactericidal activity of various anionic surfactants against Staphylococcus aureus.
• Evaluating the impact of different concentrations of inorganic cations, particularly divalent ones.
• Analyzing the adsorption of surfactants onto bacterial cell surfaces.

Main Results:

• Low concentrations of divalent cations, specifically alkaline earths and Group IIB metals, significantly increased the bactericidal effectiveness of alkyl benzene sulfonates and other anionic surfactants against Staphylococcus aureus.
• The proposed mechanism involves cations reducing the negative charge on the bacterial cell surface, thereby enhancing surfactant anion adsorption.
• This increased adsorption leads to damage of the cytoplasmic membrane and bacterial cell death.
• While increased surfactant adsorption was observed with Escherichia coli, it did not result in cell death.

Conclusions:

• Divalent inorganic cations can potentiate the bactericidal activity of anionic surfactants against Gram-positive bacteria like Staphylococcus aureus.
• The mechanism involves cation-mediated enhancement of surfactant adsorption to the bacterial cell surface, leading to membrane disruption.
• The effect is specific to bacterial species, as demonstrated by the differential response of Escherichia coli.