In vitro resistance to the CSalphabeta-type antimicrobial peptide ASABF-alpha is conferred by overexpression of sigma factor sigB in Staphylococcus aureus.
OBJECTIVE
ASABF (Ascaris suum antibacterial factor) is a CSalphabeta-type antimicrobial peptide isolated from nematodes. ASABF-alpha, a member of ASABF, is particularly effective against the gram-positive pathogen Staphylococcus aureus. In this study, we investigated the role of sigB expression on ASABF-resistance in S. aureus.


METHODS
Based on preliminary characterization of the ASABF-resistant strain, Mu50, we speculated that the alternative sigma factor sigB may regulate resistance against antimicrobial peptides. To test this hypothesis, the ASABF susceptibility was compared between NKSB (a sigB-knockout derivative of N315) and its sigB-overexpressing derivative. In addition, similar experiments were carried out for N315ex, a deletion mutant of N315 for SCCmec (Staphylococcus cassette chromosome mec) which contains essential genes for beta-lactam resistance.


RESULTS
The sigB-overexpressing NKSB acquired an increased resistance to ASABF-alpha compared with the parent strain. The sigB-induced ASABF-alpha resistance was also observed in N315ex.


CONCLUSIONS
The overexpression of sigB confers resistance to the antimicrobial peptide, ASABF-alpha. SCCmec is not essential for this resistance.
Zhang
Hong
H
Department of Developmental Biology, National Institute of Agrobiological Sciences, Oowashi 1-2, Tsukuba, Ibaraki 305-8634, Japan.
Morikawa
Kazuya
K
Ohta
Toshiko
T
Kato
Yusuke
Y
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D024881:Drug Resistance, Bacterial; D015964:Gene Expression Regulation, Bacterial; D015801:Helminth Proteins / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D046915:Penicillin-Binding Proteins; D010455:Peptides; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
C102532:ASABF protein, Ascaris suum; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015801:Helminth Proteins; D046915:Penicillin-Binding Proteins; D010455:Peptides; C079011:SigB protein, Bacteria; D012808:Sigma Factor; C487789:mecA protein, Staphylococcus aureus