Figure 1.

The impact of the deletion of stk1 and stp1 genes in S. aureus MW2 growth and cell wall structure. (A) Growth patterns of the S. aureus MW2-wild-type, MW2ΔSTK1, and MW2ΔSTP1 strains in Chemically defined medium (CDM) supplemented with 1% carbohydrate (glucose, maltose, lactose, or galactose). Growth kinetics were measured in 96-well plates at 37 °C for 16 hours under constant rotation in a final volume of 200 µl using sterile 96-well plates. Optical density at 620 nm was measured at every 15 min. Data at each time point represent an O.D. value (mean ± SD) obtained from three different experiments and each with quadruple wells for each strain. O.D. was measured spectrophotometrically as described in the Materials and Methods. Growth curves are shown in Red – MW2-wild-type strain; Black – MW2ΔSTK1 mutant; Blue – MW2ΔSTP1 mutant strains. (B–D) Transmission electron microscopy (TEM) at a low resolution of (B) wild-type MW2 and corresponding isogenic (C) ΔSTK1 and (D) ΔSTP1 mutants. The wild-type and mutant strains were grown in TSB, fixed in the glutaraldehyde and paraformaldehyde fixative and subsequently subjected to transmission electron microscopy as described in Materials and Methods. Inset bar-1.0 µm. (E–G) TEM of (B–D) at a higher resolution. Inset bar-500 nm.