Overexpression of Sigma Factor, ςB, Urges Staphylococcus aureus to Thicken the Cell Wall and to Resist β-Lactams

Genetic characterization of the natural SigB variants found in clinical isolates of Staphylococcus aureus

“…EtBr staining of the rRNAs (bottom panel) indicates the equal loading of the RNAs. copy number plasmid decreased the susceptibility to oxacillin (Morikawa et al, 2001), while the expression of sigB in a pYT3 low copy number plasmid does not (Cui et al, 2005). We had expected that b-lactam resistance might be different between C1 and N, but no significant difference was detected.…”

“…S. aureus strains used in this study are listed in Table 1, except for the clinical isolates described below. The isolation of the sigB knockout mutant (NKSB) from N315 (Kuwahara-Arai et al, 1996) has been described elsewhere (Morikawa et al, 2001). The construction of the plasmid overexpressing sigB was mentioned previously.…”

“…Then it was blunt- ended and self-ligated to generate pRIT 5H, in which the spa promoter is followed by the multi-cloning-sites and terminator region. This plasmid was used to construct the sigB overexpressing plasmid, pRIT-sigBn (Morikawa et al, 2001). The pRIT-sigBn was introduced into NKSB to generate NKSBn (Morikawa et al, 2001).…”

“…This plasmid was used to construct the sigB overexpressing plasmid, pRIT-sigBn (Morikawa et al, 2001). The pRIT-sigBn was introduced into NKSB to generate NKSBn (Morikawa et al, 2001). The plasmid was maintained stably in the presence of 12.5 mg/ml of chloramphenicol.…”

“…Via such a complex regulatory system, the SigB activity is finely regulated (Bischoff et al, 2001a;Giachino et al, 2001), and can affect various phenotypes in response to a wide range of stresses or growth conditions (Bateman et al, 2001;Benson and Haldenwang, 1993;Bischoff et al, 2001b;Cheung et al, 1999;Dorschner et al, 2006;Giachino et al, 2001;Karlsson and Arvidson, 2002;Kullik et al, 1998;Nair et al, 2003;Price et al, 2002;Rachid et al, 2000;Somerville et al, 2003;Zhang et al, 2005;Ziebandt et al, 2001). We have also reported that artificial SigB overexpressing cells have thick cell walls, high carotenoid content, and reduced susceptibility to antimicrobial peptides and cellwall affecting antibiotics (Morikawa et al, 2001;Zhang et al, 2005). Based on these findings, we assumed that there might be some correlation between the SigB concentration and the resistances to the stresses such as antibiotics.…”