title: Variation in expression of sex factor genes in the Proteus-Providencia group relative to Escherichia coli.
abstract: Several instances of anomalous expression of genes introduced from Escherichia coli K-12 into Proteus mirabilis have been described. It is shown here that control of sex pilus synthesis directed by the F-like R factor R1 and its depressed derivatives R1-16 (O-C) and R1-19 (i-minus) is also anomalous in P. mirabilis. Piliation in cells bearing the depressed plasmids is expressed at a lower level than in E. coli K-12, and repression is absent in R1-carrying cells. Preliminary results show a similar effect in Providencia. In Proteus morganii, a similarly reduced level of piliation in R1-16-+ or R1-19-+ cultures is observed, but an intermediate level of repression occurs in R1-+ cultures. Less extensive data suggest that expression of the sex factor genes of an R factor of the N incompatibility group differs far less between E. coli and P. mirabilis hosts. Possible bases for these effects are discussed.
mesh_terms: D003090:Coliphages / Q000378:metabolism; D003227:Conjugation, Genetic; D004267:DNA Viruses; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000378:metabolism*; D005144:F Factor; D005796:Genes; D009154:Mutation; D010641:Phenotype; D010957:Plasmids; D011511:Proteus / Q000254:growth & development / Q000378:metabolism*; D011532:Providencia / Q000378:metabolism; D011815:R Factors; D014161:Transduction, Genetic