D-alanine deprivation of Bacillus subtilis teichoic acids is without effect on cell growth and morphology but affects the autolytic activity.

Using insertional inactivation of the different genes of the dlt operon in Bacillus subtilis, we searched for metabolic and morphological changes caused by D-alanine ester deprivation of lipoteichoic acid and wall teichoic acid. There were no alterations of cell growth, basic metabolism, cellular content of phosphorus-containing compounds, ultrastructure, cell separation, and surface charge. The only alteration observed was an enhancement of endogenous and beta-lactam-induced cell lysis. Since this enhancement is doubtless correlated with the D-alanine ester deprivation of the teichoic acids, the present view based on in vitro experiments, that negatively charged LTA is inhibitory to autolysins, may be questioned. We propose that negatively charged lipoteichoic acid and/or wall teichoic acid serve in vivo to fix the cationic autolysins within the cell wall-membrane complex by electrostatic interaction. Positively charged D-alanine ester substituents decrease the binding capacity of the teichoic acids for autolysins by charge compensation.

Microcalorimetric and electron microscopic investigation on the effects of essential oil from Cymbopogon densiflorus on Staphylococcus aureus.

Microcalorimetry, optical density measurements and electron microscopy, were used to assess the influence of various amounts of the essential oil of Cymbopogon densiflorus (lemongrass oil) on the metabolic activity, growth and morphology of Staphylococcus aureus. Relatively high concentrations of the oil impaired staphylococcal growth in a bacteriostatic manner (chloramphenicol type), and in low doses metabolism became ineffective due to energy losses in the form of heat. Ultrastructural data revealed morphological changes characteristic for the influence of bactericidal antibiotics inducing bacteriolysis (penicillin type). The essential oil may have antibacterial activity by influencing bacterial targets involved in cytoplasmic and cell wall metabolism.

Treponema pallidum in early syphilitic lesions in humans during high-dosage penicillin therapy. An electron microscopical study.

The alterations of early syphilitic infection occuring in the course of high dosage penicillin (120 mega IU, 36 h) as clinical experimental trial has been studied both from the clinical and the electron microscopical views. By electron microscopical studies, findings revealing the localization and the status of treponemes before and during penicillin treatment could be established. Before treatment started, the majority of treponemes was of intercellular localization. In the course of treatment various forms of destruction could be differentiated. The most striking change in the host tissue after 7-8 h of penicillin therapy was an elimination of treponemes by penetrating phagocytes. 24 h after the beginning of treatment, treponemes could not be demonstrated any more. The clinical and serological findings after the high dosage penicilline will produce results comparable to those of conventional therapie.