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Lactoferrin and transferrin damage of the gram-negative outer membrane is modulated by Ca2+ and Mg2+
R T Ellison1, F M LaForce, T J Giehl
1Medical Service, Department of Veterans Affairs Medical Center, Little Rock, Arkansas.
Abstract:
Lactoferrin and transferrin have antimicrobial activity against selected Gram-negative bacteria, but the mechanism of action has not been defined. We studied the ability of lactoferrin and transferrin to damage the Gram-negative outer membrane. Lipopolysaccharide release by the proteins could be blocked by concurrent addition of Ca2+ and Mg2+. Addition of Ca2+ also blocked the ability of lactoferrin to increase the susceptibility of Escherichia coli to rifampicin. Transferrin, but not lactoferrin, increased susceptibility of Gram-negative bacteria to deoxycholate, with reversal of sensitivity occurring with exposure to Ca2+ or Mg2+. In transmission electron microscopy studies polymyxin B caused finger-like membrane projections, but no morphological alterations were seen in cells exposed to EDTA, lactoferrin or transferrin. These data provide further evidence that lactoferrin and transferrin act as membrane-active agents with the effects modulated by Ca2+ and Mg2+.
Insights
Lactoferrin and transferrin damage Gram-negative bacteria outer membranes, with effects modulated by calcium and magnesium ions. This reveals their antimicrobial mechanism against bacteria.
Area of Science:
- Microbiology
- Biochemistry
Background:
- Lactoferrin and transferrin exhibit antimicrobial properties against Gram-negative bacteria.
- The precise mechanism of action, particularly concerning the bacterial outer membrane, remains incompletely understood.
Purpose of the Study:
- To investigate the capacity of lactoferrin and transferrin to disrupt the Gram-negative bacterial outer membrane.
- To elucidate the role of divalent cations, specifically calcium (Ca2+) and magnesium (Mg2+), in modulating these interactions.
Main Methods:
- Assessing lipopolysaccharide (LPS) release from bacterial membranes upon protein treatment.
- Evaluating changes in bacterial susceptibility to antibiotics (rifampicin) and detergents (deoxycholate) in the presence of proteins and cations.
- Utilizing transmission electron microscopy (TEM) to visualize morphological changes in bacterial cells.
Main Results:
- Lipopolysaccharide release was inhibited by the simultaneous addition of Ca2+ and Mg2+.
- Ca2+ blocked lactoferrin-induced increased susceptibility of Escherichia coli to rifampicin.
- Transferrin, unlike lactoferrin, enhanced bacterial sensitivity to deoxycholate, an effect reversed by Ca2+ or Mg2+.
- TEM revealed no significant morphological alterations induced by lactoferrin or transferrin, contrasting with polymyxin B.
Conclusions:
- Lactoferrin and transferrin function as membrane-active agents against Gram-negative bacteria.
- The antimicrobial effects of these proteins are significantly modulated by the presence of Ca2+ and Mg2+ ions, influencing their interaction with the bacterial outer membrane.