Normal serum cytotoxicity for P32-labeled smooth Enterobacteriaceae. II. Fate of macromolecular and lipid phosphorus of damaged cells

Spitznagel, John K. (University of North Carolina, Chapel Hill). Normal serum cytotoxicity for P(32)-labeled smooth Enterobacteriaceae. II. Fate of macromolecular and lipid phosphorus of damaged cells. J. Bacteriol. 91:148-152. 1966.-Fresh, normal adult guinea pig serum released micro- and macromolecular forms of metabolically incorporated P(32) from smooth Escherichia coli. A significant amount of P(32)-labeled phospholipid was also released. The overall acid solubility distribution of the P(32) label in bacterial suspensions was very little affected in fresh serum, although P(32)-labeled cytoplasmic contents and cell walls of E. coli lost some P(32) when they were suspended in fresh or heat-inactivated normal serum. These findings confirmed and extended earlier evidence that the peripheral wall and membrane structures of smooth E. coli are extensively damaged by factors in fresh normal serum.

The inhibition of ribosomal ribonuclease by bacterial ribosomes

1. A comparison has been made between the ribonuclease activities of untreated ribosomes from Escherichia coli B and Pseudomonas fluorescens and the activities of ribosomes on to which ribosomal ribonuclease from E. coli B has been adsorbed. 2. The normal ribosomes from both species were stable in 5-10mm-Mg(2+) (I0.16) at pH6. The RNA in ribosomes from Ps. fluorescens was attacked by the adsorbed ribonuclease under these conditions, whereas the ribosomes from E. coli B were able to adsorb and inhibit this enzyme. 3. Inhibition was also observed with ribosomes from Aerobacter aerogenes, Proteus vulgaris and two other strains of E. coli. It was not observed in ribosomes from three species of Pseudomonas. 4. The inhibition depended on the integrity of the ribosomes and was not observed under conditions of low Mg(2+) concentration that cause irreversible degradation into more slowly sedimenting particles.

Effects of toluene on Escherichia coli

Jackson, Robert W. (University of California, San Diego, La Jolla), and J. A. DeMoss. Effects of toluene on Escherichia coli. J. Bacteriol. 90:1420-1425. 1965.-When toluene is added at appropriate levels to exponentially growing cultures of Escherichia coli, a time-dependent loss of turbidity is observed which is concurrent with a loss of material to the medium and with unmasking of beta-galactosidase. In addition, the galactoside permease system is totally destroyed. Electron micrographs confirm the indications that the cells are not being lysed by toluene, although the cytoplasm collapses to the interior of the cell. Included in the material lost from the cell after toluene treatment is 85% of the total ribonucleic acid (RNA), the principal source of which appears to be the ribosomes. The loss of RNA is temperature-dependent. Protein is also lost to the medium as a function of both temperature and available toluene. Up to 25% of the total protein is found in the medium, the precise amount depending on the level of toluene employed. Zone centrifugation studies of extracts from treated cells indicate that toluene elicits a rapid disaggregation of ribosomes that is terminated, at any stage, by disruption of the cells. The disaggregation is temperature-dependent and does not occur at 4 C. It appears to be distinct from the actual degradation of ribosomal RNA and is accompanied by an accumulation of small particles during the initial phases of treatment at 21 C. Toluene added to crude extracts of normal E. coli cells is unable to cause detectable ribosome destruction.

Chemical fractionation of phosphorus-32 labelled cells of Micrococcus lysodeikticus treated with chlorhexidine

A method for the chemical fractionation of Micrococcus lysodeikticus into “cold trichloroacetic acid soluble”, alcohol soluble, ribonucleic acid and residual fractions is described. The results of applying this method to untreated and chlorhexidine-treated 32P labelled cells are discussed. In untreated cells the 32P content of the “cold trichloroacetic acid soluble” fraction, which constitutes the metabolic pool, increases at a rate dependent on temperature increase and there is a corresponding decrease in the 32P content of the ribonucleic acid fraction. At the highest temperature, 40°, the increase of 32P in the pool is followed by a decrease due to leakage from the pool. The release of 32P from chlorhexidine-treated cells maintained at 1 °, 20°, 30° and 40° has been measured after 0.5, 2 and 13 hr. There is an initial rapid release which is entirely from the “cold trichloroacetic acid soluble” fraction and a slower secondary release from the ribonucleic acid fraction. This secondary release is almost completely inhibited at 1° and by high (64 and 128 μ.g/ml) chlorhexidine concentrations.