The morphology of induced wall-defective variants of Streptococcus faecalis as studied by light and electron microscopy

Abstract

Study by light microscopy of induced wall-defective variants of Streptococcus faecalis was undertaken to examine the sequential development of these forms during a 36-day period. Particularly noted were the early cell wall deficient forms observed at 36 h which appear as "cartwheels." Evolution of these forms through the various stages of the granular-appearing colonies to the classical "fried egg" morphology is described. A similar developmental pattern was observed with both a prototype of the test organism as well as with a fresh isolate from the genitourinary tract of a patient.Colonies of induced wall-defective variants of S. faecalis grown on an induction medium were examined in the electron microscope by use of the technique of ultrathin sectioning. This study was undertaken to examine, at the cellular level, the colonial morphology of these variants and to describe differences existing in specified areas of the colony. Longitudinal thin sections of the induced wall-defective colonies were prepared from three levels of the colonies as they related to the medium surface: supraagar surface; subagar surface; and deep subagar. Examination of the thin sections offers evidence that the bacterial population in a single colony is morphologically heterogeneous.