RESUMEN
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.
Asunto(s)
Péptidos Catiónicos Antimicrobianos/farmacología , Membrana Celular/efectos de los fármacos , Potenciales de la Membrana/efectos de los fármacos , Proteínas de Plantas/farmacología , Sinorhizobium meliloti/efectos de los fármacos , Péptidos Catiónicos Antimicrobianos/metabolismo , Membrana Celular/ultraestructura , Medicago truncatula/fisiología , Microscopía de Fuerza Atómica , Microscopía Electrónica de Rastreo , Proteínas de Plantas/metabolismo , Polimixina B/farmacología , Nódulos de las Raíces de las Plantas/fisiología , Sinorhizobium meliloti/crecimiento & desarrollo , Sinorhizobium meliloti/ultraestructuraRESUMEN
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.
