Nuclear segregation and the delayed appearance of induced mutants in Escherichia coli

The existence of a cytologically demonstrable nucleus in the bacterial cell is no longer seriously in question. There is, however, no direct evidence that the Feulgen-positive staining bodies generally considered to represent the nuclear or chromosomic elements of the bacterium are actually carriers of genetic material. The chromosome theory of heredity has yet to be established for bacteria. Current acceptance of the bacterial nucleus as a cytological entity stems largely from the work of investigators who demonstrated bodies having typically nuclear reactions to stains and enzymes (Stille, 1937; Piekarski, 1940; Robinow, 1945; Tulasne and Vendrely, 1947, among others). Although there is no general agreement among bacterial cytologists as to the finer organization and structure of the nuclear body, and as to its pattern of division (see Delaporte, 1950; Bisset, 1950; Knaysi, 1951), the observation that serves as the starting point of this investigation is, I believe, sufficiently conservative to find general acceptance: namely, that the number of visibly distinct nuclear bodies (or chromosomes, or nuclear elements) is larger in logarithmically dividing cells of Escherichia coli than in resting cells

Effect of nucleic acid on phenomic lag in Escherichia coli

When a series of 50 tubes of broth containing 0.5% sodium ribonucleate (Schwartz) is inoculated with strain B/r of Escherichia coli, the cultures obtained after 48 hours of incubation contain, on the average, a significantly higher number of mutants resistant to bacteriophage T 1 than a similar series of cultures grown without nucleate

Effects of temperature on spontaneous and induce mutations in Escherichia coli

The frequency of spontaneous mutations in Drosophila has been shown to increase, in general, with increasing temperature, and the temperature coefficients reported range from about 2 to 5(1). These findings played an important part in the early definition of mutation as a definite molecular rearrangement(2). Very little is known of the response to post-treatment temperature of mutations induced by radiation or chemicals. Two kinds of effects could be investigated in this connection: the effect of temperature on the frequency of induced mutations, and the effect of temperature on the pattern of delayed appearance of induced mutations. In the latter category, Auerbach(3) has described an increase in the frequency of mustard-induced mosaics at low temperatures, which she ascribes to the stabilization by cold of metastable genic configurations induced by the mutagen, leading to extended delay in the shift to the stable mutant condition. Similar effects of temperature on the delayed action of mutagens in Neurospora and Aspergillis found in unpublished experiments by the authors are mentioned by McElroy and Swanson(4) in support of the concept of mutation via metastable intermediates. The hereditary change from sensitivity to resistance to bacteriophage in Escherichia coli can be followed with a degree of quantitative precision and technical ease that makes it a promising material for an investigation of temperature effects on spontaneous and induced mutation. This report is a preliminary account of such a study

A supressor mutation in Escherichia coli

Nutritionally deficient mutant strains of bacteria (auxotrophs) are often capable of undergoing "reversion," giving rise to strains having the wild type nutritional state (prototrophs). It is usually impossible to determine whether the prototrophs are true back-mutants, or whether the wild phenotype is restored by the action of an independent suppressor mutation. An auxotroph requiring histidine was isolated from strain B/r of Escherichia coli (which grows well on minimal medium) after ultraviolet irradiation and layering(1). Some time later, the histidineless strain was irradiated with ultraviolet and subjected to penicillin screening(2,3) Among the mutants isolated was one requiring serine or glycine in addition to histidine. This diauxotroph, strain M2, was thus characterized by two growth factor requirements acquired separately and serially, presumably by two mutational steps

Bacterial Communities of the Coronal Sulcus and Distal Urethra of Adolescent Males

Lactobacillus-dominated vaginal microbiotas are associated with reproductive health and STI resistance in women, whereas altered microbiotas are associated with bacterial vaginosis (BV), STI risk and poor reproductive outcomes. Putative vaginal taxa have been observed in male first-catch urine, urethral swab and coronal sulcus (CS) specimens but the significance of these observations is unclear. We used 16 S rRNA sequencing to characterize the microbiota of the CS and urine collected from 18 adolescent men over three consecutive months. CS microbiotas of most participants were more stable than their urine microbiotas and the composition of CS microbiotas were strongly influenced by circumcision. BV-associated taxa, including Atopobium, Megasphaera, Mobiluncus, Prevotella and Gemella, were detected in CS specimens from sexually experienced and inexperienced participants. In contrast, urine primarily contained taxa that were not abundant in CS specimens. Lactobacilllus and Streptococcus were major urine taxa but their abundance was inversely correlated. In contrast, Sneathia, Mycoplasma and Ureaplasma were only found in urine from sexually active participants. Thus, the CS and urine support stable and distinct bacterial communities. Finally, our results suggest that the penis and the urethra can be colonized by a variety of BV-associated taxa and that some of these colonizations result from partnered sexual activity

Inherited Differences in Sensitivity to Radiation in Escherichia Coli

The study of spontaneous and radiation-induced mutations is at present our best approach to the investigation of genetic mechanisms in bacteria. Mutations involving resistance to destructive agents (bacteriophage (1) penicillin(2)) are especially suitable for genetic analysis, since resistant mutants can easily be detected in bacterial cultures. This preliminary report concerns a mutation in Escherichisa Coli leading to resistance to both ultraviolet radiation and x-rays, which was detected by exposing samples from normal cultures to high doses of radiatio

The Use of Sodium Nucleate in the Study of the Mutagenic Activity of Acriflavine in Escherichia Coli

In a previous study(1) neutral acriflavine was shown to induce mutations from phage-sensitivity to phage-resistance in Escherichia coli. The present report concerns an improved method of investigating the mutagenic potency of certain compounds, using acriflavine as a model