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

Abstract

Abstract. 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

“…Prolonging the treatment for 3 h caused no further changes, cells treated for 1 and 3 h were alike. These observations were in line with reported surface corrugation of the E. coli cell envelope by NCR247 [ 18 ]. Similar study on the NCR335 treated S. meliloti cultures could not be performed as the bacteria lost their attachment to the poly- l -lysine coated muscovite mica surface.…”

“…For example, NCR247 (pI = 10.15) and NCR335 (pI = 11.22) are both effective against gram-negative and gram-positive bacteria [ 16 ] as well as fungi [ 17 ], however their spectrum of activity is not identical (see [ 1 ] and Additional file 1 ) suggesting that in addition to the net positive charge, the amino acid composition and sequence contribute also to their activities. Investigation of NCR247 and NCR335 treated Escherichia coli cells by atomic force microscopy (AFM) revealed increased surface roughness suggesting the damage of the cell envelope [ 18 ].…”

Sinorhizobium fredii HH103 bacteroids are not terminally differentiated and show altered O‐antigen in nodules of the Inverted Repeat‐Lacking Clade legume Glycyrrhiza uralensis

“…Although the very different susceptibility of S. meliloti 1021 and S. fredii HH103 was unexpected, this is also the case for Escherichia coli and Salmonella typhimurium , two closely related members of the family Enterobacteriaceae that strongly differ in their response to NCR247 and NCR335 (Tiricz et al ., ). Very recently, it has been shown by in situ atomic force microscopy studies that NCR247 and NCR335 caused damage to the bacterial cell envelope when applied to E. coli or on natural purple membrane, most likely affecting the lipid matrix (Nagy et al ., ). The fact that S. fredii HH103 and S. meliloti 1021 present remarkable differences in their cell envelopes, at least in their exopolysaccharide (EPS) and in their capsular polysaccharide (KPS) (Fraysse et al ., 2003; 2005; Margaret et al ., ; Rodríguez‐Navarro et al ., ), might be one reason for their different sensitivities to the two NCR peptides tested.…”

Identification of sequences encoding for ncr-peptides and defensins in the ‘meta-assembly’ of transcriptome of pea (pisum sativum l.) Nitrogen-fixing nodules

“…Nodule-specific Cysteine Rich), которые, вероятно, также являются частью иммунной системы клубенька [7]. Предполагают, что NCR-пептиды, как и дефензины, выполняют свои биологические функции в том числе за счет проявления антимикробной активности [12][13][14][15][16].…”