Induction of streptomycin resistance in sensitive Hemophilus influenzae by extracts containing desoxyribonucleic acid from resistant Hemophilus influenzae

Abstract

Resistance to streptomycin, of a degree exceeding 1000 microg. per ml., has been induced in sensitive strains of Hemophilus influenzae by exposure for 10 minutes to desoxyribonucleic acid-containing extracts isolated from a strain of type b Hemophilus influenzae which had emerged resistant to 1000 microg. of streptomycin per ml. DNA is essential for the process which brings out this change; the reaction can be prevented by destruction of the DNA with crystalline desoxyribonuclease.The resistant trait which is created in this way is heritable. The nature of the process which induces resistance is similar in all respects to the reaction which induces heritable changes in type specificity of H. influenzae. These results offer another example of the gene-like action of highly specific DNA's. The pattern of resistance brought out in a bacterial population exposed to the DNA-containing, resistance-inducing extract, is similar to that which occurs when emergence of resistance of H. influenzae to streptomycin follows the selection by streptomycin of spontaneously occurring resistant mutants. The change in a bacterial cell from average susceptibility to streptomycin to resistance to 1000 microg. of streptomycin per ml. can occur in a single step.