Induction of Lysogenic Bacteria as a Method of detecting Potential Antitumour Agents

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.

A simple plate test for screening colicine-inducing substances as a tool for the detection of potential carcinogens

A simple and rapid plate test is described for screening substances that induce colicine E2. By using chemicals activated with microsomal enzymes and a permeable (rfa) tester bacterium that is also deficient in DNA repair (uvrB), the range of inducing substances that can be detected has been extended. The possible correlation between colicine-inducing substances and carcinogens is discussed.

Inhibition of DNA synthesis by griseolutein in Escherichia coli through a possible interaction at the cell surface

Griseolutein acts as a bactericidal agent, its toxicity decreasing with increase in cell density. There is no evidence that griseolutein acts at a specific stage of cell cycle. Inhibition of incorporation of radioactive thymidine into acid-insoluble fraction of cells is marked and rapid, while inhibition of incorporation of uridine also takes place. Incorporation of 32Pi into the acid-insoluble fraction of cells is inhibited while the incorporation into the nucleotide pool is not. Concentration of any of the four deoxyribonucleoside triphosphates in griseolutein-treated cells are similar to or higher than those in untreated cells. No extensive degradation of cellualr DNA is caused by griseolutein. DNA synthesis in plasmolyzed cells in not inhibited by griseolutein.

[Search for nucleic acid influencing, as well as membrane active, potential cancerostatic fungal metabolites using microbiological and cytological screening methods]

A prescreening program including microbiological and cytological assays was employed in search of potential cancerostatic antibiotics in crude extracts of mushrooms. The microbiological tests based on agar diffusion techniques consist of prophage induction test and BIP-test. All active compounds selected by these microbiological models are potential inhibitors of nucleic acid metabolism. Cytological assays on leukemia L 1210 cells have been carried out by microscopic examination and by evaluation using an electronic particle counter. Activity was expressed as decrease of the number of single cells caused by agglutination or lysis of cells, changes in cell surface area, dye exclusion, and increase of cell volume. A wide variety of mushrooms was demonstrated to exhibit interesting activities in some of these screening systems. The influence of primary metabolic products of mushrooms on microbiological models was studied additionally. In vivo assays have not yet been accomplished.

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.

Rapid plate test for evaluating phage induction capacity

An agar plate test is presented as a screening test for phage induction capacity of various chemicals.

Biological effects of aflatoxin in cell culture

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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.