Regulation of bacterial cell walls: correlation between autolytic activity and cell wall turnover in Staphylococcus aureus

Cell wall turnover was examined in parent and mutant strains of Staphylococcus aureus. Peptidoglycan and teichoic acid were observed to undergo turnover in the wild-type strain during exponential growth; however, the rate of turnover did not decrease when the growth rate slowed, as the culture entered stationary phase. Isolated native cell walls and crude soluble autolytic enzyme were prepared from cells harvested during exponential and postexponential phases of growth. Native cell walls from both phases of growth autolyzed in buffer at identical rates; similarily, crude soluble enzyme from both preparations degraded radioactive cell walls at the same rate. Therefore, the activity of the autolysin in both exponential and postexponential cells was similar. The autolysis of whole cells of a mutant tar-1 was enhanced by 1.0 M NaCl. When 1.0 M NaCl was present under growing conditions, the rate of cell wall turnover was greatly increased. The presence of chloramphenicol, which inhibits whole-cell autolysis, also inhibited turnover. Analysis of the cell wall material recovered from spent medium revealed products consistent with the known mode of action of the endogenous autolysin. It is concluded that cell wall turnover in S. aureus is independent of the stage of culture growth but is dependent instead on the activity of the autolysin.

Isolation and characterization of a mutant of Staphylococcus aureus deficient in autolytic activity

A mutant of Staphylococcus aureus H (RUS3) uas isolated after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. The rate of autolysis of whole cells and isolated cell walls of RUS3 was less than 10% of the parent strain. In addition, the ability of the crude soluble enzyme isolated from RUS3 to degrade cell walls was negligible compared with the parent strain. The cell wall composition and the generation time of RUS3 were comparable to the parent strain. Unlike S. aureus H, RUS3 grew in clumps and did not undergo cell wall turnover. Both strains exhibited identical kinetics of killing by penicillin G. This may indicate that autolytic enzymes play a role in cell wall turnover and cell separation, but in S. aureus most of the autolytic activity is unrelated to the lethal effect of cell wall antibiotics.

Radiologic detection and prostatic carcinoma by double contrast retrograde urethrocystography

A method of radiologic visualization of the male urethra especially for detecting prostatic carcinoma is reported. This method is called double contrast retrograde urethrocystography and is similar to that of Flocks in combining air cystography and retrograde urethrography but it differs in the manner of making the exposure. In our method the exposure is made with the patient in an exaggerated Trendelenburgs position to allow the contrast medium injected into the bladder to accumulate at the dome. Thus, in the urethrocystogram obtained by this method, the bladder neck and the prostatic urethra immediately adjacent to it are always clearly visualized unlike that obtained by conventional retrograde urethrography, evacuation cystourethrography and sometimes even the method of Flocks, in which these regions are prone to be covered and masked by the contrast medium injected and accumulated in the bladder. Therefore, with our method the radiological detection and differentiation of the malignant lesion involving these regions are more accurate and definite. From our clinical experiences the mode of compression and displacement caused by benign prostatic hypertrophy is continuous and regular, while that caused by prostatic carcinoma is interrupted, irregular and with moth-eaten and granular defects. Four cases are reported.

Isotope Fractionation in Photosynthetic Bacteria during Carbon Dioxide Assimilation

The delta (PDB) (13)C values have been determined for the cellular constituents and metabolic intermediates of autotrophically grown Chromatium vinosum. The isotopic composition of the HCO(3) (-) in the medium and the carbon isotopic composition of the bacterial cells change with the growth of the culture. The delta (PDB) (13)C value of the HCO(3) (-) in the media changes from an initial value of -6.6 per thousand to +8.1 per thousand after 10 days of bacterial growth and the delta (PDB) (13)C value of the bacterial cells change from -37.5 per thousand to -29.2 per thousand in the same period. The amount of carbon isotope fractionation during the synthesis of hexoses by the photoassimilation of CO(2) has a range of -15.5 per thousand at time zero to -22.0 per thousand after 10 days. This range of fractionation compares to the range of carbon isotope fractionation for the synthesis of sugars from CO(2) by ribulose 1,5-diphosphate carboxylase and the Calvin cycle.The amount of carbon isotope fractionation during the synthesis of aspartic acid from CO(2) is -24.9 per thousand at time zero and -15.0 per thousand after 10 days of bacterial growth. This amount of fractionation is in the range of carbon isotope fractionation for the synthesis of C(4) amino acids by a double carboxylation through ribulose 1,5-diphosphate and phosphoenolpyruvate carboxylase.

Regulation of bacterial cell walls: turnover of cell wall in Staphylococcus aureus

The cell wall of Staphylococcus aureus was shown to undergo turnover during exponential growth. The rate of turnover, about 15% per generation, was identical for both cell wall polymers, peptidoglycan and teichoic acid. Both the old and newly synthesized wall material appeared to undergo turnover at similar rates. The rate of turnover followed first-order kinetics until more than 90% of the original wall was lost. Cell wall turnover was completely blocked under conditions of unbalanced synthesis known to inhibit cellular autolysis, e.g., addition of chloramphenicol. Cell wall turnover was shown to occur in a number of different strains of S. aureus and appears to be widely distributed in this species.

Autolysis in Staphylococcus aureus: preferential release of old cell walls

The kinetics of release of old versus new cell wall in two strains of Staphylococcus aureus were studied during autolysis. In both strains the autolytic enzyme is an amidase. Cells were double labeled with (3)H and (14)C, and the distribution of radioactivity in the cell walls was monitored during autolysis. In all cases the rate of release of steady-state lable from peptidoglycan was significantly higher than that of pulse label. Identical results were obtained with whole cells or isolated cell walls. The results suggest that in S. aureus the old cell wall is preferentially released during autolysis.