Comparison of two transformation systems for the assay of theNeurosporaphotoreactivating enzyme

Abstract

SUMMARY: TheNeurospora crassaphotoreactivating enzyme has been assayed for by theHemophilus influenzaeandBacillus subtilistransformation systems. In contrast to theH. influenzaesystem, u.v.-treated transforming DNA fromB. subtilisdid not give evidence of reactivation of u.v. lesions by crude enzyme extracts fromN. crassawhen exposed to photoreactivating light. The u.v. dose required to inactivateB. subtilistransforming DNA is about ten times that required to inactivateH. influenzaeDNA to the same level of survival. This difference in dose required to inactivate DNA's of about the same base composition probably reflects the greater u.v. resistance of theB. subtilisrecipient strains used. Hypotheses are considered which suggest thatN. crassacrude enzyme extracts contain either nucleases which degradeB. subtilistransforming DNA excessively or an inhibitory factor which affects the transformation process itself.