Dual antibacterial mechanisms of nisin Z against Gram-positive and Gram-negative bacteria.
Nisin, an amphipathic antibiotic peptide, is produced by a number of strains of Lactococcus lactis subsp. lactis. It has been employed as a food preservative as it has a high antibacterial activity with a relatively low toxicity for humans. Nisin is known to exert a high antibacterial activity against Gram-positive but not Gram-negative bacteria. However, purified nisin Z was found to show an antibacterial activity both against Gram-positive and Gram-negative bacteria. To clarify the mechanisms of activity, nisin Z and purified nisin Z were tested for their antibacterial activities in a high-salt environment. The activity of nisin Z against Staphylococcus aureus was stable even in the presence of NaCl at 100 mM, showing ca. 2log colony-forming unit (CFU) reduction. In contrast, the activity of nisin Z against Escherichia coli was highly sensitive to the same concentration of NaCl, and CFU reduction was not observed. Furthermore, purified nisin Z caused the permeabilisation both of S. aureus and E. coli cytoplasmic membranes. The permeabilisation of E. coli but not S. aureus cytoplasmic membranes was remarkably reduced in a high-salt environment. Moreover, vancomycin inhibited the nisin Z-induced permeabilisation of the S. aureus cytoplasmic membrane. These results suggest that nisin Z utilises two distinct mechanisms of antibacterial activity: a high-salt-sensitive mechanism for E. coli and a high-salt-insensitive mechanism for S. aureus.
Kuwano
Koichi
K
Department of Bacteriology, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan. kuwano@med.kurume-u.ac.jp
Tanaka
Noriko
N
Shimizu
Takashi
T
Nagatoshi
Kohei
K
Nou
Shinsuke
S
Sonomoto
Kenji
K
D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D009561:Nisin / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000494:pharmacology; D010539:Permeability / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000378:metabolism; D014640:Vancomycin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D009561:Nisin; D012965:Sodium Chloride; D014640:Vancomycin; C071364:nisin Z