L-Az-aserine as an inducing agent for the development of phage in the lysogenic Escherichia coli, K-12

Phage-host interactions: The neglected part of biological wastewater treatment

In wastewater treatment plants (WWTPs), the stable operation of biological wastewater treatment is strongly dependent on the stability of associated microbiota. Bacteriophages (phages), viruses that specifically infect bacteria and archaea, are highly abundant and diverse in WWTPs. Although phages do not have known metabolic functions for themselves, they can shape functional microbiota via various phage-host interactions to impact biological wastewater treatment. However, the developments of phage-host interaction in WWTPs and their impact on biological wastewater treatment are overlooked. Here, we review the current knowledge regarding the phage-host interactions in biological wastewater treatment, mainly focusing on the characteristics of different phage populations, the phage-driven changes in functional microbiota, and the potential driving factors of phage-host interactions. We also discuss the efforts required further to understand and manipulate the phage-host interactions in biological wastewater treatment. Overall, this review advocates more attention to the phage dynamics in WWTPs.

SYSTEM FOR DETECTING INDUCERS OF LYSOGENIC ESCHERICHIA COLI W1709 (LAMBDA) AND ITS APPLICABILITY AS A SCREEN FOR ANTINEOPLASTIC ANTIBIOTICS

Studies were conducted to determine conditions of maximal sensitivity for a test system designed to detect chemical inducers of phage production in the streptomycin-dependent, lysogenic Escherichia coli strain W1709(lambda). This strain was found to be induced by all antibiotics previously reported to be inducers of E. coli K-12(lambda). However, the system employing W1709(lambda) proved superior for screening fermentation filtrates because its growth, in contrast to that of K-12(lambda), was not stimulated during the induction period by filtrate nutrients. Thus, misleading high phage counts, which accompany cell growth stimulation, were not produced by filtrates devoid of inducing activity. The inducing capability of 95 fermentation filtrates, each containing an unidentified antibiotic(s) inhibitory for one or more transplanted rodent tumors, was determined in the W1709(lambda) system. A low incidence of inducers was found among inhibitors of sarcoma 180, adenocarcinoma 755, solid myeloid leukemia C1498, and adenocarcinoma of the duodenum in the hamster. However, seven of eight filtrates active against leukemia 1210 had induction capability. From a screen of actinomycete culture filtrates, 28 of the first 1,000 were identified as producers of induction activity. Thus far, of the nine cultures from this group that were subjected to examination, eight demonstrated at least presumptive evidence of antineoplastic activity.

Azaserine: further evidence for DNA damage in Escherichia coli

Azaserine causes DNA damage in stationary-phase cells. In our investigation of this damage, we used strains of Escherichia coli differing in repair capabilities to study azaserine-induced DNA damage, detected as DNA strand breaks by sucrose gradient sedimentation techniques. Reduced sedimentation in alkaline and neutral sucrose gradients indicated the presence of both alkali-labile sites and in situ strand breaks. Azaserine induced DNA single-strand breaks (SSBs) abundantly in all but the recA strain, in which SSBs were greatly reduced. Treatment of purified DNA with azaserine from bacteriophages T4 and PM2 produced no detectable SSBs. Several other studies also failed to detect DNA damage induced directly by azaserine. Increased levels of beta-galactosidase were induced in an E. coli strain possessing a rec::lac fusion, providing further evidence for azaserine induction of the recA gene product. In addition, azaserine induced adaptation against killing but not against mutagenesis in wild-type E. coli strain.

Enhancing activity of rat tissue extracts for induction of lambda prophage by L-azaserine

We studied the effect of rat tissue extracts on induction of lambda prophage in Escherichia coli (lambda) by L-azaserine. Hepatic and pancreatic extracts, primarily the cytosolic fraction, markedly increased the rate of induction. Hepatic extracts from lipotrope-deficient rats were somewhat more active than extracts from normal rats. The enhancing activity in normal rat hepatic cytosol was partially characterized. It reduced by about one-half the dose of azaserine required for a given purpose. The enhancement was increased by preincubating the bacterial cells with cytosol; cells retained the effect after cytosol was removed. Enhancing activity was inhibited strongly by the amino acids phenylalanine, tryptophan, and tyrosine; to lesser extents by leucine, methionine, and serine; and not at all by proline or glutamine. It was eliminated by dialysis of the cytosol and reduced by omission of nicotinamide adenine dinucleotide phosphate (NADP) from the reaction mixture. Heating the cytosol to 60 degrees C or 80 degrees C or varying the pH of the reaction mixture from 6 to 8 had no significant effect. Treating the cytosol with trypsin appeared to release an inhibitor of the activity. Glutathione, cysteine, and beta-mercaptoethanol also enhanced lambda induction by azaserine, but the cytosolic activity was not affected by the thiol-inactivating compound diethylmaleate (DEM). The results suggest that factors in cytosol interact with bacterial cells to facilitate transport of azaserine into the cells, primarily through the aromatic amino acid transport system. A small molecule, not a free thiol compound, appears to be involved. It may serve to establish reducing conditions protective for azaserine, the probable mechanism of action of sulfhydryl compounds.

Azaserine: survival and mutation in Escherichia coli

Azaserine in an antineoplastic agent, mutagen and carcinogen that is known to inhibit purine metabolism. Comparison of mutation in stationary-phase cultures of E. coli WP2 and a series of its DNA repair-deficient mutants exposed to azaserine showed that the effects of the compound closely mimicked those caused by UV light indicating, therefore, that azaserine-induced mutagenesis occurred via pathways dependent upon the recA and lexA genes. Comparison of survival of these strains showed that potentially lethal DNA lesions induced by azaserine were corrected by the excision, recombination, and rec-lex repair systems. These results show that azaserine causes DNa damage as well as inhibition of purine metabolism.

Aflatoxin B1 induction of lysogenic bacteria

A technique for biological verification of aflatoxin B(1) was developed based on toxin-mediated induction of lysis in a lysogenic strain of Bacillus megaterium NNRL B-3695. Reduction of culture turbidity was determined at various concentrations of toxin. Incubation of 1.1 x 10(-4) g (dry weight) of cells/ml of growth medium containing 25 mug of B(1) per ml at 37 C reduced initial turbidity 0.20 absorbance units in 4 hr. If the bacterial lysate of the lysogenic strain, after a 2-hr incubation with 25 mug of B(1) per ml, was plated with a sensitive B. megaterium strain (NRRL B-3694), plaque-forming units increased approximately 150 times relative to the control. Comparable testing of the effects of aflatoxin on the nonlysogenic, sensitive strain demonstrated that 75 mug of B(1) per ml neither induced lysis nor plaque-forming units. Although induction is not an exclusive property of aflatoxin B(1), the differential response of the lysogenic and sensitive Bacillus strains to B(1) offers a unique and rapid technique for biological verification of the toxin.

Induction of Lambda-Bacteriophage in Escherichia coli as a Screening Test for Potential Antitumor Agents

A simple, rapid, quantitative test procedure to measure induction of phage production in lysogenic Escherichia coli K-12 (λ) was described. This test was used in a study of 209 substances, including antibiotics, pyrimirines, purines, alkylating agents, thiols, amino acids, vitamins, and miscellaneous compounds. Minimal inducing concentrations for the 26 (12.5% of total tested) substances found to be effective inducing agents, as well as a listing of the inactive compounds, are presented. Since 21 of the 26 active agents reportedly have antineoplastic activity in rodent tumor systems, it was concluded that the induction test may provide a useful screen for the detection of potentially useful antitumor compounds.

INDUCTION OF LYSOGENIC MICROCOCCUS LYSODEIKTICUS

Field , A. K. (Cornell University, Ithaca, N.Y.) and H. B. Naylor . Induction of lysogenic Micrococcus lysodeikticus . J. Bacteriol. 84: 1129–1133. 1962.—Between 50 and 60% of log-phase cells of Micrococcus lysodeikticus strain ML 53-40, lysogenic for N5 bacteriophage, were induced by an optimal dose of ultraviolet light. Induction of dilute cell suspensions caused a subsequent 200- to 800-fold increase in infective-center concentration. Cells in the stationary growth phase and cells adapted to a chemically defined medium were also induced by ultraviolet irradiation. Dimethyl sulfate induced the lysogenic culture to about the same extent as did ultraviolet light, whereas β-propiolactone was less effective.

Cytological analysis of ultraviolet irradiated Escherichia coli. II. Ultraviolet induction of lysogenic E. coli

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