ON SOME GENETIC ASPECTS OF PHAGE Λ RESISTANCE IN E. COLI K12

[摘要] Most mutations rendering E . coli K12 resistant to phage λ, map in two genetic regions mal A and mal B.—The mal B region contains a gene lam B specifically involved in the λ receptor synthesis. Twenty-one independent lam B mutations studied by complementation belonged to a single cistron. This makes it very likely that lam B is monocistronic. Among the lam B mutants some are still sensitive to a host range mutant of phage λ. Mutations mapping in a proximal gene essential for maltose metabolism inactivate gene lam B by polarity confirming that both genes are part of the same operon. Because cases of intracistronic complementation have been found, the active lam B product may be an oligomeric protein.—Previously all λ resistant mutations in the mal A region have been shown to map in the mal T cistron. mal T is believed to be a positive regulatory gene necessary for the induction of the "maltose operons" in the mal A region and in the mal B region of the E . coli K12 genetic map. No trans dominant mal T mutation have been found. Therefore if they exist, they occur at a frequency of less than 10–8, or strongly reduce the growth rate of the mutants.

[学科分类] 医学（综合）