Physiological studies on pBR 322 DNA amplification in an XXXX relA strain.

@entity17136 @entity368 @entity535 @entity3793 @entity3265 @entity377 @entity1391 @entity14474 @entity413 @entity1889 @entity369 @entity526
@entity535 limitation leads in @entity526 relA cells which cannot synthesize @entity17136 (ppGpp) under these conditions to an amplification of pBR 322 DNA. We previously proposed that ppGpp produced in @entity526 relA+ cells subjected to @entity535 limitation inhibits pBR 322 DNA replication (Hecker et al. 1983). In further experiments it was established that an @entity526 relA strain shows plasmid amplification during @entity535 limitation ( @entity369 , @entity1889 , @entity368 or @entity3793 ) only in the presence of sufficient concentrations of @entity1391 , @entity3265 and @entity413 . Plasmid amplification does not occur if @entity3265 or @entity1391 is depleted. We suggest that @entity413 , @entity3265 and @entity1391 are needed for @entity377 and deoxynucleotide synthesis as the essential prerequisite for plasmid amplification. The activity of @entity14474 was determined as an indicator for the expression of plasmid-encoded genes. The enzyme activity remains on a low level during plasmid amplification because of @entity369 exhaustion. A remarkable increase in the activity of @entity14474 was observed after resumption of growth of relA cells containing amplified plasmid DNA. The plasmid content decreased as the cells continued to grow. We found that plasmid amplification and expression of plasmid-localized genes are opposite reactions which do not occur at the same time.
