Scanning-beam electron microscopy of cell wall-defective staphylococci.

Staphylococci and their derived wall-defective forms (WDS) were studied with Gram stain, phase microscopy, and the scanning-beam electron microscope. Staphylococci were smooth, spherical, and relatively uniform in size. Stable WDS had corrugated surfaces and were larger; those prepared with lysostaphin were indistinguishable from those prepared with methicillin. During induction of WDS in methicillin-containing hypertonic broth, WDS were first observed after 7 hr of incubation and progressively, thereafter, increased in number. They were larger than the stable WDS and varied more in size and shape. Microscopically, "wisps" were seen to consist of WDS, persistent parent staphylococci, and residual cell membranes.