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Light and Scanning-Beam Electron Microscopy of Wall-Defective Staphylococcus aureus Induced by Lysostaphin ¹

Infectious Disease Division, Department of Internal Medicine, University of Cincinnati College of Medicine and the Cincinnati General Hospital, Cincinnati, Ohio 45229
Division of Infectious Diseases, Department of Medicine, the Ohio State University College of Medicine, Columbus, Ohio 43210

ABSTRACT

The serial morphological changes of Staphylococcus aureus after exposure to lysostaphin (one unit per ml) in hypertonic culture medium containing 5% NaCl were studied over an 8-hr period at 37 C. S. aureus stained gram-negative almost instantaneously upon contact with lysostaphin. Many cells were lysed, but wall-defective staphylococci with corrugated surface were detected as early as 5 min by use of scanning-beam electron microscopy. Wall-defective staphylococci enlarged progressively with increasing periods of incubation. The absorbance of the lysostaphin-treated culture decreased significantly by 2 min, remained stationary for 2 hr, and then progressively increased. The number of vegetative colony-forming units decreased progressively with increasing periods of incubation, whereas the number of L-colony-forming units remained the same.

² Deceased 29 July 1970.

¹ Presented at the annual meeting of the Midwest Section of the American Federation for Clinical Research, Chicago, Ill., 4-6 November 1970.