{'fraction_non_alphanumeric': 0.04953031596925705, 'fraction_numerical': 0.007685738684884714, 'mean_word_length': 3.9661016949152543, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Repression of induction by U.V. of lambda phage by exrA mutations in Escherichia coli.

The effect of ultraviolet radiation (u.v.) on λ lysogens of exrA strains of Escherichia coli was studied. exrA strains could be lysogenized with, as well as support the vegetative reproduction of, λ. However, though spontaneous induction of λ occurred in exrA (λ) strain at 10% the frequency of exrA + (λ) strain, exrA (λ) strains were not induced by u.v. Because λ was not induced in exrA (λ) strains, lysogens of these strains were no more sensitive to u.v. than were non-lysogens. The heat-inducible mutant λ hcI857 could be induced in exrA strains at elevated temperatures. Furthermore, u.v. irradiation of exrA (λ hcI857 ) strain did not prevent the heat induction of this λ mutant. The exrA mutation appeared to interfere only with the inactivation of λ repressor by u.v. Among the exrA strains studied was strain Bs 1( exr A uvrB ). Whereas the λ lysogen of strain Bsl could not be induced by u.v. and was no more sensitive to u.v. than its non-lysogen, the exrA + uvrB (λ) derivative of strain Bsl could be induced by u.v. and was more sensitive to u.v. than its non-lysogen.