Effect of human defensins on lactobacilli and liposomes

HUGO, A. A.; TYMCZYSZYN, E. E.; GÓMEZ ZAVAGLIA, A. AND PÉREZ, P. F.

JOURNAL OF APPLIED MICROBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2012 vol. 113 p. 1491 - 1497

1364-5072

Aims: to study the effect of human defensins (HBD-1 and HBD-2) on lactobacilli membranes as well as on liposomes prepared from purified bacterial lipids. Methods and Results: Lactobacillus delbrueckii subsp. bulgaricus CIDCA 331 and Lactobacillus delbrueckii subsp. lactis CIDCA 133 were grown in MRS broth for 16 h at 37ºC. After being washed, microorganisms were treated with 0.1 to 10 mg/mL of HBD-1 and HBD-2 (30 min, 37ºC). Bacterial damage was determined by flow cytometry after propidium iodide (PI) staining. In parallel experiments, release of carboxyfluoresceine from liposomes prepared from bacterial lipids was determined fluorometrically (excitation 485/20 nm, emission 528/20 nm) in the presence of HBD-1, HBD-2 or Nisin. Exposure of lactobacilli to HBD-2 resulted in a significant membrane permeabilization being Lactobacillus delbrueckii subsp. bulgaricus CIDCA 331 the most susceptible strain. Liposomes prepared with lipids from strain CIDCA 133 were destabilized neither by HBD-1 nor by HBD-2 whereas liposomes derived from strain CIDCA 331 were susceptible to HBD-2 but not to HBD-1. Effect of defensins was strongly inhibited in the presence of NaCl and the activity increased in water. Conclusions: Results reported in the presented work indicate that lipid composition of bacterial membranes lead to a different interaction with cationic peptides such as defensins. Significance and Impact of the study: The results represent an advance in the understanding of the differential effect of HBDs on microorganisms. Differences in susceptibility to antimicrobial peptides could modify the fate of microorganisms after the interaction with host´s cells.