Atomic force microscopy study of magainin 2 versus human platelet extract action on Escherichia coli and Bacillus cereus

Cationic AntiMicrobial Peptides (CAMPs) are specific antibiotic agents with strong bactericidal properties and are considered as a one of the alternative ways to treat the resistant forms of bacteria (Rautenbach & Hastings, 1999; Hancock & Patrzykat, 2002; Alves et al., 2010). CAMPs have been isolated from single-cell microorganisms, plants, amphibians, birds, fish, and mammals (Hancock & Diamond, 2000; Zasloff, 2002). They have also been found in human platelets (Krijgsveld et al., 2000). Many of these peptides have been extensively studied in order to elucidate their antimicrobial mode of action. Study of the efficacy of new antimicrobial drugs should be carried out using different methods. Microscopy is one of the informative methods for understanding effects of various factors on bacterial cells. Among the various microscopic techniques, the Atomic Force aicroscopy (AFM) can be distinguished (Dufrêne, 2002). AFM is a relatively new technique that has provided new opportunities for the surface analysis of biological specimens with nanoscale resolution and minimal effect on the sample structure. AFM can be used not only for visualization but also to probe local surface forces and mechanical properties of biomaterials (Gaboriaud & Dufrêne, 2007). These benefits make it possible to use AFM for cellular and intracellular structures investigations, yielding information on cell wall assembly and dynamics that cannot be obtained with traditional microscopy techniques (Dorobantu & Gray, 2010). AFM can also be used to study the effect of drugs on microbial cell walls (Cerf et al., 2009; Perry et al., 2009). One of the first works concerning the application of AFM to investigate the antibiotics effect on bacteria was made by Braga & Ricci (1998). In this work, the authors studied qualitatively the morphological and surface alterations of E. coli induced by various concentrations of the ‚-lactam antibiotic cefodizime. Meincken et al. (2005) used AFM for the analysis of the membranolytic effects in the mechanisms of action of three antimicrobial peptides by using E. coli cells as the live bacterial target. A highspeed AFM technique has allowed investigating kinetics of antimicrobial peptide activity measured on Atomic force microscopy study of magainin 2 versus human platelet extract action on Escherichia coli and Bacillus cereus