The effect of free chlorine onEscherichia coli populations

The effect of free chlorine onEscherichia coli populations was studied by chlorination of a population of 10⁵ cells/ml. This cell density was low enough for the free-to-combined chlorine ratio to be 6.01 or greater. The predominance of free chlorine resulted in rapid and complete population death.Survivors obtained by dechlorination prior to complete population death were recovered equally well on nonselective and selective media. Although this suggests that survivors are not injured, evidence of survivor injury was observed.Colonies resulting from growth of these survivors had a smaller diameter than colonies from unchlornated controls. This suggests that the chlorinated cells have an increased lag and provides indirect evidence of survivor injury. Injury was indicated directly by an increase in the lag time of surviving cells in slide culture. Variability in the severity of free-chlorine-induced injury was indicated by a broadened range in the survivor lag times.     

Effect of ferricyanide onEscherichia coli

Ferricyanide, ferrocyanide and phosphates in concentrations greater than 0.07 M inhibit the respiration of NAD-linked substrates and succinate in washed cell suspension ofE. coli. Citrate accumulation in the medium under the inhibiting conditions indicates that these salts bring about a change in the permeability of the cell membrane of this bacterium.In general, ferricyanide does not resemble in action those compounds which uncouple respiratory-energy production. Energy production is prevented only when ferricyanide is the main electron acceptor. The inhibition studies and the addition of co-factors, indicate that cytochromes are not involved in the reduction of ferricyanide by cell-free extracts ofE. coli, either with NADH or succinate. An FAD-containing enzyme is probably involved in the reduction of ferricyanide by NADH, while succinic dehydrogenase seems to react directly with ferricyanide.We wish to thank Group Capt. Tom Gray-Young for technical advice and R. Filzroy for technical assistance.This work was supported by a grant from the Science Research Council.     

Multiplicity of phosphorylation sites onEscherichia coli isocitrate dehydrogenase

Several lines of evidence indicate that the in vivo phosphorylation of isocitrate dehydrogenase (EC 1.1.1.42) inEscherichia coli occurs at multiple sites: first, the phosphorylated enzyme can be resolved by two-dimensional electrophoresis into three distinct spots differing in charge; second, the analysis of its phosphoamino acid content shows that it is modified at both serine and threonine residues; third, its extensive hydrolysis by proteolytic enzymes yields several different phosphopeptides.     

Differential inhibitory effects of actinomycin D among strains of poliovirus

Schaffer, Frederick L. (University of California, Berkeley), and Marjorie Gordon. Differential inhibitory effects of actinomycin D among strains of poliovirus. J. Bacteriol. 91:2309-2316. 1966.-Actinomycin D exerted a differential effect on the ability of strains of poliovirus to replicate in HeLa cells. LSc-2ab was studied as an example of a strain markedly inhibited by actinomycin; MEF(1) served as a control strain with minimal inhibition. The effect was noted at an actinomycin concentration of 0.1 mug/ml, but 2.5 mug/ml was used for most studies. Variability in the effect was attributed, in part, to physiological factors. Actinomycin was effective when present during the first 2 hr of LSc infection, but had little effect if present at later times. It did not block adsorption or initiation of ecilpse. It did block synthesis of ribonucleic acid in LSc-infected cells. Several possible modes of action are discussed, the most attractive being that actinomycin blocks synthesis of some cell component, the concentration of which is more critical for replication of some poliovirus strains than others.     

New data on the toxic and radioprotective effect of cysteine onEscherichia coli 15 T- cells

Summary Exponential phase cultures ofE. coli 15 T^- cells growing on glucosemineral medium were supplemented with 2 mM l-cysteine-HCl. The optical density, acid soluble SH (AS-SH) as well as the DNA, RNA, and protein synthesis of the cultures were examined during this treatment and after return to normal growth conditions. Similarly, the survival of cells irradiated by a standard X-ray dose in cysteine-free buffer was measured.The development of radioresistance during the cysteine treatment as well as the loss of this acquired radioresistance after return to normal growth conditions could be divided into two phases: a) an instantaneous and b) a slow change of radioresistance. Phase a seems to be related to the changes occurring in the AS-SH content of the bacteria, while phase b is apparently dependent on the alterations in the synthesis of macromolecules.This work was partly presented at the 6th Annual Meeting of the European Society for Radiation Biology, Interlaken 1968.     

Effect of the essential oil fromAchillea fragrantissima onEscherichia coli cells

Escherichia coli cells treated with the essential oil from the plantAchillea fragrantissima released five polypeptides as well as K⁺ ions into the incubation medium. The oil also inhibited the respiration ofE. coli cells and reduced their ATP content. Electron micrographs showed that oil-treated cells were permeable to uranyl acetate. The effect of the essential oil on the cell membrane is discussed.     

The effect of actinomycin D on hemopoiesis. I. Short-term effects

The effect of in vivo administration of actinomycin D (Act D) on the hemopoietic precursor compartments and, in particular, the BFU-E, CFU-E, and erythroblast populations was investigated over a 6-day period. Daily injections of mice with 15 microgram/kg, 30 microgram/kg, and 60 microgram/kg Act D showed a dose-dependent effect. The highest dose caused an almost complete eradication of CFU-E as well as the morphologically identifiable erythroblasts. There was no appreciable reduction in BFU-E, GM-CFU, and CFU-S. These observation indicate that Act D interferes with erythropoiesis by selectively inhibiting the CFU-E compartment. The effects are not due to altered sensitivity to erythropoietin as dose response curves were similar for control and Act D-treated cells. Although a considerable reduction in CFU-E is observed and approximately 20-30% of nucleated cells are lost from the small size region, there is no displacement in the velocity sedimentation profiles either from the remaining CFU-E and nucleated cell populations or the BFU-E and GM-CFU populations.     

The effect of actinomycin D on the formation of gametangia and mitosporangia in Allomyces

The effect of actinomycin on gametangium and mitosporangium production in Allomyces arbuscula and A. macrogynus has been investigated. Male gametangium production was not more sensitive to actinomycin than female development. Actinomycin at 20 g/ml added at the commencement of induction was completely inhibitory. The process became insensitive to actinomycin just before the first septum was laid down.     

Inductive effects of environmental concentration of atrazine onEscherichia coli andEnterococcus faecalis

Atrazine solutions (0.1, 1, 10 and 100 microg/L) inoculated with Escherichia coli and Enterococcus faecalis under natural conditions significantly increased (p < or = 0.05) the population levels of both test bacteria; it indicates the ability of bacterial cells to degrade atrazine and to use the original compound or its degradation products as nutrient(s). In some cases, alterations in the morphology of the colonies were also observed on selective solid media. Biochemical differentiation was also found and, on the other hand, a loss of culturability was recorded; this suggests that bacteria have entered in a viable but nonculturable state. A re-appearance of the colonies occurred after inoculation on tryptone-soy agar with atrazine.