Limits...
Killing of staphylococci by θ-defensins involves membrane impairment and activation of autolytic enzymes.

Wilmes M, Stockem M, Bierbaum G, Schlag M, Götz F, Tran DQ, Schaal JB, Ouellette AJ, Selsted ME, Sahl HG - Antibiotics (Basel) (2014)

Bottom Line: We found that in contrast to other defensins, RTDs do not interfere with peptidoglycan biosynthesis, but rather induce bacterial lysis in staphylococci by interaction with the bacterial membrane and/or release of cell wall lytic enzymes.In addition, RTD treatment caused the release of Atl-derived cell wall lytic enzymes probably by interaction with membrane-bound lipoteichoic acid.Interestingly, a similar mode of action has been described for Pep5, an antimicrobial peptide of bacterial origin.

View Article: PubMed Central - PubMed

Affiliation: Institute of Medical Microbiology, Immunology and Parasitology, University of Bonn, 53105 Bonn, Germany.

ABSTRACT

θ-Defensins are cyclic antimicrobial peptides expressed in leukocytes of Old world monkeys. To get insight into their antibacterial mode of action, we studied the activity of RTDs (rhesus macaque θ-defensins) against staphylococci. We found that in contrast to other defensins, RTDs do not interfere with peptidoglycan biosynthesis, but rather induce bacterial lysis in staphylococci by interaction with the bacterial membrane and/or release of cell wall lytic enzymes. Potassium efflux experiments and membrane potential measurements revealed that the membrane impairment by RTDs strongly depends on the energization of the membrane. In addition, RTD treatment caused the release of Atl-derived cell wall lytic enzymes probably by interaction with membrane-bound lipoteichoic acid. Thus, the premature and uncontrolled activity of these enzymes contributes strongly to the overall killing by θ-defensins. Interestingly, a similar mode of action has been described for Pep5, an antimicrobial peptide of bacterial origin.

No MeSH data available.


Related in: MedlinePlus

Transmission electron microscopy of S. aureus SG511-Berlin treated with 10x MIC RTD-2. (A) Untreated control cells. (B, C) Cells treated for 30 min. Additional membranous structures could be observed. (D, E, F) Cells treated for 60 min. Dividing cells showed degradation of the cell wall in the septum area between two daughter cells (D, E) or peeling of the cell wall (F). Scale bar: 0.2 μm.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4306331&req=5

Figure 4: Transmission electron microscopy of S. aureus SG511-Berlin treated with 10x MIC RTD-2. (A) Untreated control cells. (B, C) Cells treated for 30 min. Additional membranous structures could be observed. (D, E, F) Cells treated for 60 min. Dividing cells showed degradation of the cell wall in the septum area between two daughter cells (D, E) or peeling of the cell wall (F). Scale bar: 0.2 μm.

Mentions: RTD-treated cells of S. aureus SG511-Berlin grown in half-concentrated MHB were inspected by transmission electron microscopy. After 30 min treatment, additional membranous structures could be observed in many cells (Figure 4 A-C), indicating the loss of cytoplasmic content. After 60 min exposure to RTD-2, cells showed evidence of cell wall degradation, particularly in the septum area between two daughter cells (Figure 4 D and E). Moreover, in some cells, the cell wall was completely peeled off (Figure 4 F). These morphological changes might indicate a premature activation and release of peptidoglycan lytic enzymes (referred to as autolysins) involved in cell separation as has been described for Pep5-treated cells [33]. These results suggest that the release of autolysins, which hydrolyze the glycan chains and peptide bridges of murein, also contributes to the killing activity of RTDs.


Killing of staphylococci by θ-defensins involves membrane impairment and activation of autolytic enzymes.

Wilmes M, Stockem M, Bierbaum G, Schlag M, Götz F, Tran DQ, Schaal JB, Ouellette AJ, Selsted ME, Sahl HG - Antibiotics (Basel) (2014)

Transmission electron microscopy of S. aureus SG511-Berlin treated with 10x MIC RTD-2. (A) Untreated control cells. (B, C) Cells treated for 30 min. Additional membranous structures could be observed. (D, E, F) Cells treated for 60 min. Dividing cells showed degradation of the cell wall in the septum area between two daughter cells (D, E) or peeling of the cell wall (F). Scale bar: 0.2 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4306331&req=5

Figure 4: Transmission electron microscopy of S. aureus SG511-Berlin treated with 10x MIC RTD-2. (A) Untreated control cells. (B, C) Cells treated for 30 min. Additional membranous structures could be observed. (D, E, F) Cells treated for 60 min. Dividing cells showed degradation of the cell wall in the septum area between two daughter cells (D, E) or peeling of the cell wall (F). Scale bar: 0.2 μm.
Mentions: RTD-treated cells of S. aureus SG511-Berlin grown in half-concentrated MHB were inspected by transmission electron microscopy. After 30 min treatment, additional membranous structures could be observed in many cells (Figure 4 A-C), indicating the loss of cytoplasmic content. After 60 min exposure to RTD-2, cells showed evidence of cell wall degradation, particularly in the septum area between two daughter cells (Figure 4 D and E). Moreover, in some cells, the cell wall was completely peeled off (Figure 4 F). These morphological changes might indicate a premature activation and release of peptidoglycan lytic enzymes (referred to as autolysins) involved in cell separation as has been described for Pep5-treated cells [33]. These results suggest that the release of autolysins, which hydrolyze the glycan chains and peptide bridges of murein, also contributes to the killing activity of RTDs.

Bottom Line: We found that in contrast to other defensins, RTDs do not interfere with peptidoglycan biosynthesis, but rather induce bacterial lysis in staphylococci by interaction with the bacterial membrane and/or release of cell wall lytic enzymes.In addition, RTD treatment caused the release of Atl-derived cell wall lytic enzymes probably by interaction with membrane-bound lipoteichoic acid.Interestingly, a similar mode of action has been described for Pep5, an antimicrobial peptide of bacterial origin.

View Article: PubMed Central - PubMed

Affiliation: Institute of Medical Microbiology, Immunology and Parasitology, University of Bonn, 53105 Bonn, Germany.

ABSTRACT

θ-Defensins are cyclic antimicrobial peptides expressed in leukocytes of Old world monkeys. To get insight into their antibacterial mode of action, we studied the activity of RTDs (rhesus macaque θ-defensins) against staphylococci. We found that in contrast to other defensins, RTDs do not interfere with peptidoglycan biosynthesis, but rather induce bacterial lysis in staphylococci by interaction with the bacterial membrane and/or release of cell wall lytic enzymes. Potassium efflux experiments and membrane potential measurements revealed that the membrane impairment by RTDs strongly depends on the energization of the membrane. In addition, RTD treatment caused the release of Atl-derived cell wall lytic enzymes probably by interaction with membrane-bound lipoteichoic acid. Thus, the premature and uncontrolled activity of these enzymes contributes strongly to the overall killing by θ-defensins. Interestingly, a similar mode of action has been described for Pep5, an antimicrobial peptide of bacterial origin.

No MeSH data available.


Related in: MedlinePlus