System for Detecting Inducers of Lysogenic Escherichia coli W1709(λ) and Its Applicability as a Screen for Antineoplastic Antibodies

Abstract

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(λ). This strain was found to be induced by all antibiotics previously reported to be inducers of E. coli K-12(λ). However, the system employing W1709(λ) proved superior for screening fermentation filtrates because its growth, in contrast to that of K-12(λ), 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(λ) 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.