TABLE 2.

Inducers of liaI expression

InduceraDisk diffusion assaybConcn (μg/ml)cIncrease (n-fold) in induction ± SDd
BFS2470HB0950
Cell wall antibiotics
    Ampicillin
    Bacitracin+10498 ± 92192 ± 16
    Cephalosporin
    D-cycloserin
    Fosfomycin(+)101.7 ± 0.6
    Moenomycin
    Nisin+10423 ± 16156 ± 8.3
    Penicillin G
    Polymyxin B
    Ramoplanin+5422 ± 60144 ± 12
    Tunicamycin+503.1 ± 1.1
    Vancomycin+263 ± 2.736 ± 0.2
Organic solvents
    Diphenyl etherNT1010.8 ± 3.4
    n-HexaneNT107.8 ± 1.2
    CyclooctaneNT1011.6 ± 4.9
Surfactantse
    BDMDDA-Br
    BDMHDA-Cl+108.2 ± 1.9
    HDTMA-Br
  • a Strong inducers are in bold.

  • b Qualitative screen of β-galactosidase activity in strain BFS2470; activity was assessed by the appearance of a blue ring around the edge of the zone of inhibition on LB plates supplemented with X-Gal. −, no induction; +, induction of liaI expression; (+), very weak induction in disk diffusion assays; NT, not tested.

  • c The concentration resulting in the highest level of induction was used.

  • d Quantitative β-galactosidase assay in liquid with the pMUTIN-derived (strain BFS2470; Table 1) and pJPM122-derived minimal promoter system (strain HB0950; Table 1). Cells were cultured in LB medium to mid-log phase and induced by the addition of the drug to be tested to the final concentration given. Cells were harvested and the assay was performed as described in Materials and Methods. Results are expressed as the increase relative to uninduced control. The background activity for the uninduced samples was about 3 to 5 (strain BFS2470) and 0.5 (strain HB0950) Miller units.

  • e BDMDDA-Br, benzyldimethyldodecylammonium bromide; BDMHDA-Cl, benzyldimethylhexadecylammonium chloride; HDTMA-Br, hexadecyltrimethylammonium bromide.