FIG 6.

A mutation in spxB, but not in lctO, renders S. pneumoniae (Spn) unable to kill S. aureus (Sau) in a microplate model. S. aureus strain Newman (∼1 × 10⁶ CFU/ml) was inoculated alone (Ctrl) or along with the indicated S. pneumoniae strains (∼1 × 10⁶ CFU/ml) in microplates containing THY and incubated for 4 h at 37°C. Bacteria were harvested and then diluted and plated onto SMA (A and B) or BAP with gentamicin (C and D) to obtain counts of S. aureus planktonic cells (A), S. aureus biofilms (B), S. pneumoniae planktonic cells (C), or S. pneumoniae biofilms (D). The error bars represent the standard errors of the means calculated using data from at least three independent experiments. (A and B) *, P < 0.05 compared to S. aureus control incubated alone. (D) For comparison, the median (CFU per milliliter) is shown inside two of the bars.