Interaction of cysteine-rich cationic antimicrobial peptides with intact bacteria and model membranes

Antimicrobial peptides are small proteins that exhibit a broad spectrum of antimicrobial activity. Their chemical structure allows them to interact (attach and insert) with membranes. The fine details about this interaction and their mode of action are not fully clarified yet. In order to better understand this mechanism, we have performed in situ atomic force microscopy studies using two types of nodule specific cysteine-rich NCR peptides on Escherichia coli bacteria and on natural purple membrane. On intact bacteria, both NCR247 and NCR335 caused increase in the surface roughness, indicating the damage of the bacterial cell envelope. In case of the tightly packed purple membrane, it is clear that the peptides prefer to disrupt the border of the disks indicating a strong lipid preference of the interaction. These results verify the concept that the first target of NCR peptides is probably the bacterial cell envelope, especially the lipid matrix

Antimicrobial nodule-specific cysteine-rich peptides disturb the integrity of bacterial outer and inner membranes and cause loss of membrane potential

Background: Certain legume plants produce a plethora of AMP-like peptides in their symbiotic cells. The cationic subgroup of the nodule-specific cysteine-rich (NCR) peptides has potent antimicrobial activity against gram-negative and gram-positive bacteria as well as unicellular and filamentous fungi. Findings: It was shown by scanning and atomic force microscopies that the cationic peptides NCR335, NCR247 and Polymyxin B (PMB) affect differentially on the surfaces of Sinorhizobium meliloti bacteria. Similarly to PMB, both NCR peptides caused damages of the outer and inner membranes but at different extent and resulted in the loss of membrane potential that could be the primary reason of their antimicrobial activity. Conclusions: The primary reason for bacterial cell death upon treatment with cationic NCR peptides is the loss of membrane potential.ISSN:1476-071

MOESM1 of Antimicrobial nodule-specific cysteine-rich peptides disturb the integrity of bacterial outer and inner membranes and cause loss of membrane potential

Additional file 1. Minimal Bactericid concentration of the NCR247 and NCR335 peptides on different gram-positive and gram-negative bacteria