Autolytic Enzyme System of Streptococcus faecalis IV. Electron Microscopic Observations of Autolysin and Lysozyme Action

Abstract

Cell walls (LOG walls) were isolated from cultures of Streptococcus faecalis ATCC 9790 in the exponential phase of growth. These walls were either allowed to undergo autolytic dissolution (in the presence or absence of trypsin) or wall autolysis was inactivated with sodium dodecylsulfate (SDS walls). Inactivated walls were treated either with lysozyme or with isolated, partially purified S. faecalis autolysin. During wall lysis, samples were removed, negatively stained with phosphotungstate, and examined in the electron microscope. Both lysozyme and isolated autolysin appeared to act over the entire surface of SDS walls. After partial dissolution, a fibrous network over the surface was revealed. Lysozyme digestion revealed the presence of prominent, highly-contrasted equatorial and subequatorial bands around the walls. After trichloroacetic acid extraction, the bands were seen less frequently and less distinctly in the partially lysozyme digested walls, suggesting that the bands contained nonpeptidoglycan polymers. In the absence of trypsin (which activates a latent form of the autolysin), autolysis of LOG walls appeared to start at the equatorial bands and to proceed back towards the apex of the coccus. Ribbons of wall material coming off the wide edge of the nearly hemispherical wall fragments were observed. Activation of latent autolysis resulted in lytic action over the entire wall surface. The results are consistent with the previously postulated location of active autolysin at the areas of new wall synthesis and the random location of latent autolysin in LOG walls.

Autolytic Formation of Protoplasts (Autoplasts) of Streptococcus faecalis 9790: Release of Cell Wall, Autolysin, and Formation of Stable Autoplasts

“…This localization is in agreement with ultrastructural observations of autolyzing walls (14) and cells (6), which show that the earliest observable damage is localized to the leading edges of nascent cross walls. On the other hand, results of both ultrastructural observations (14) and pulse chase experiments (15) carried out with isolated walls were consistent with a random localization of the latent autolysin. During disruption of intact cells the latent form, but not the active form, was found to bind, with approximately equal affinity, to exogenously added and endogenous wall.…”

“…In exponential-phase cells the active form of the autolysin has been found to be associated with recently synthesized wall (15). This localization is in agreement with ultrastructural observations of autolyzing walls (14) and cells (6), which show that the earliest observable damage is localized to the leading edges of nascent cross walls. On the other hand, results of both ultrastructural observations (14) and pulse chase experiments (15) carried out with isolated walls were consistent with a random localization of the latent autolysin.…”

Modification of cell wall polysaccharide spatially controls cell division inStreptococcus mutans

“…5f). A previous report, using electron microscopy imaging, has identified the equatorial rings as the zones of autolysin activity in E. faecalis 46 . However, since the deletion of AtlA does not affect S. mutans cell shape, other mechanisms besides AtlA might be responsible for the generation of the daughter equatorial rings.…”

Mutual Relationship between Antibiotics and Resting Spores of Bacillus subtilis: Morphological Changes and Macromolecular Synthesis after Germination of Spores Treated with Cyclic Polypeptide and Aminoglycoside Antibiotics

“…This report is the first one concerning abnormal thickness of the cell wall of bacteria belonging to genus Bacillus induced by the protein synthesis inhibitory antibiotic bound to the resting spores. The walls on valine-or threonine-starved cells of S. faecalis have been also reported to be 2.5 to 3 times thicker than those of the exponential-phase cells (9,19). Higgins and Shockman (9) divided normal cell wall growth into three distinct processes: (i) centripetal cross wall, (ii) peripheral wall extension, and (iii) wall thickening, and they assumed that the wall extension process is closely coupled with the synthesis of protein (and other macromolecules) and activity of the autolytic enzyme system, but that wall thickening is independent of these processes.…”