Decreased extrachromosomal fixation of chimeric plasmid in strain N19 ofHaemophilus influenzae Rd.
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Chromosomal DNAcarrying closely-linked genetic marker allelesstrrnovr produces roughly equivalent number of StrR (streptomycin-resistant) and NovR (novobiocin-resistant) transformants from wild type strain but widely differnt ratios (StrR50: NovR1) from a mutant strain N19. Reduction in AmpR (vector marker) extra chromosomal transformants is observed in N19 with chimeric plasmids carrying chromosomal DNA inserts fromnov region. Thus, AmpR transformants with chimeric plasmid DNA pJl-8N2 and pJl-8N19 are two to three orders of magnitude lower in N19 than in wild type. However, pJl-8NaIR33, pKuvrl, p3 and p10 DNA transform N19 and Rd with near-equal efficiency. Reduction in AmpR transformants is intermediate (30 to 100-fold lower) in strain N19 with pJ18StrR38 and pD7. These data are interpreted to suggest the presence of a small “aberration” in thenov region.
KeywordsHaemophilus influenzae strain N19 differential transformation novchimeric plasmid low extrachromosomal fixation
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