Specific Chromosomal Affinity of a Resistance Factor

The P-1 incompatibility group plasmid R772 can mobilize the chromosome of Proteus mirabilis strain ~~5 0 0 6 .The decreasing gradient of recombinant recovery frequencies found for markers which were increasingly distal to 0 min with plasmid D donors was not found with R772. Instead, it produced recombinants for all markers at frequencies of about 5 x per donor. This is about 10-fold lower than the plasmid transfer frequency. Recombinants were stable and recombination was only detected over short segments of the chromosome which corresponded to about 10 min on the D plasmid map of the chromosome. All recombinants had inherited R772 and expressed all properties of the plasmid. Attempts to isolate variant plasmids with increased frequencies of recombinant formation were unsuccessful.

Section: Discussionmentioning

confidence: 93%

Mobilization of the Proteus mirabilis Chromosome by R Plasmid R772

Coetzee

1978

“…There was definite polarity of entry of some markers and this raised the question of the relationship between P-lacR 1drd19 and the donor chromosome. The frequency of transfer of the his marker, the first of the chromosomal markers investigated to enter, was reminiscent of the transfer of the trp region of E. coli by R1drd19 (Pearce & Meynell, 1968) where it was claimed that the R factor had a special affinity for that portion of the chromosome. The latter authors as well as Cooke & suggested that this factor alternated frequently between integration near the trp region and the autonomous state.…”

Section: Discussionmentioning

confidence: 99%

“…It was evident that the plasmid P-ZacR~drd~g entered recipient cells early and at high frequency. Early and rapid transfer of R1drd19 occurred in E. coli crosses mediated by the latter plasmid (Pearce & Meynell, 1968) and in FPf x FP-Ps. aeruginosa conjugation systems the factor was also transmitted at maximal frequency soon after conjugation commenced (Stanisich & Holloway, 1969).…”

Section: Pattern Of Segregation Recombinantsmentioning

confidence: 99%

Chromosome Transfer in Proteus Mirabilis Mediated by a Hybrid Plasmid

Coetzee

1975

A previously-described fused plasmid, P-ZacR 1drd19, was found to mediate chromosomal transfer between cells of Proteus mirabilis strain ~~5 0 0 6; ~~5 0 0 6 -(P-ZacRrdrd19) was usually the donor and various auxotrophs of ~~5 0 0 6 resistant to nalidixic acid and/or streptomycin were recipients. The donor was usually counterselected with nalidixic acid and/or high concentrgtions of streptomycin. Recombination experiments with single markers indicated a 40-fold variation in recombination frequencies for different markers. Mapping double-auxotrophic markers by their gradient of transmission confirmed this variation and placed each of two independent isolates of eight markers in a linkage group his-ser-ura-pyrBtrp-cys-ade-ilv. Some donor markers did not register. Despite low recombination frequencies, interrupted mating experiments showed a polarity of early marker transfer. The segregation of unselected markers confirmed the order of some markers and showed that genetic material passed from the presumptive donor to the recipient. Recipients with two auxotrophic markers which could not be cotransduced by phage 5006M were converted to prototrophy by conjugation. The plasmid transferred to recipients at high frequency and all recombinants carried it. Recombinants could act as donors in further matings. Recombinants were fully susceptible to phage 5006M, unlike transductants of ~~5 0 0 6 by this phage. Direct involvement of the plasmid was indicated by drastically diminished recombination frequencies in crosses with recipients carrying P-lac as resident. P-lac had previously been shown to reduce the frequency of transfer of the hybrid plasmid to cells harbouring it. The histidine region was the first to register in recipients and recombined at the highest frequency of 5 x Io-6/donor cell. Some temporary association of plasmid and perhaps only the histidine region of the chromosome is favoured as the mechanism of chromosomal transfer. This could explain why not all donor markers could be mapped. Transduction and transformation were excluded as the cause of results.

“…Towner & Vivian (1976a, b) found it indispensable for the demonstration of chromosomal transfer in a strain of Acinetobacter and the membrane technique has become standard practice in transduction experiments with phage 5006M (see Coetzee, 1974b). The strict temperature requirement (37 "C) for R1-mediated E. coli intraspecies chromosomal transfer (Pearce & Meynell, 1968) was not encountered, and transfer occurred over a range of more than 10 "C in the P. mirabilis crosses with an optimum at 30 "C. This could be due to the different hosts involved or because transfer was under control of the P-lac element of the fused plasmid (see Coetzee, 1974aCoetzee, , 1975.…”

Section: Proteus Chromosome Transfer 161mentioning

confidence: 99%

Extension of a Chromosome Linkage Group of Proteus mirabilis

Coetzee¹

1978

Mating procedures for detection of mobilization of the Proteus mirabilis chromosome were re-investigated. The chromosome was mobilized by plasmid D, the previously used hybrid between plasmids P-lac and Rldrdl9. About a 40-fold increase in recombinant recovery correlated with the absence of swarming during mating and a lower temperature of incubation. The modification introduced was that conjugation was allowed to proceed on a non-selective supplemented minimal medium at 30 "C before washing and plating on selective media. Final incubation was also at 30 "C. This technique enabled eight additional chromosomal markers to be mapped. Polarized transfer of the chromosome was shown by gradient of transmission experiments using a previously described marker as reference, by linkage analysis with reference to proximal and distal markers and (less successfully) by interrupted mating on solid medium. Markers of plasmid D transferred at high frequency to all recombinants. The plasmid was stable in recombinants and could transfer itself and chromosomal markers of the new hosts in further matings. Resulting recombination of markers occurred at usual frequencies. The marker order, his-1, pyrBl, cysAl, cysGl, cysC1, argA2, metF2, nalA1, leuB2, did not resemble the order of these markers in Escherichia coli.