FIG 1.
Contact-, and density-dependent killing of S. aureus (Sau) by S. pneumoniae (Spn). (A) S. pneumoniae strain TIGR4 and S. aureus strain Newman were inoculated concurrently at the indicated densities (CFU per milliliter). Once inoculated, the plates were incubated for 24 h at 37°C. (B to D) To quantify genome equivalents per milliliter of S. pneumoniae or S. aureus, bacteria growing on spots inoculated with 108 CFU/ml of S. pneumoniae and 108 (B), 107 (C), or 106 (D) CFU/ml of S. aureus were collected; DNA was extracted; and the DNA was used as a template in species-specific qPCRs. The error bars represent the standard errors of the means calculated using data from at least three independent experiments. *, P < 0.05 compared to S. aureus control incubated alone; #, P > 0.67 compared to S. pneumoniae control inoculated alone.