Attachment of wild-type<i>F</i>factor to a specific chromosomal region in a variant strain of<i>Escherichia coli</i>K12: the phenomenon of episomic alternation

Richter, Alan

doi:10.1017/s0016672300000823

Cited by 44 publications

(12 citation statements)

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“…Release of integrated F factors is not always an exact reversal of the integration event. Sometimes a segment of chromosome is incorporated into the episome, forming an F merogenote, and a segment of the sex factor is left behind as a sex factor affinity site (219). Again, the result is a deletion (230).…”

Section: Incompatibilitymentioning

confidence: 99%

Extrachromosomal inheritance in bacteria.

Novick¹

1969

Bacteriological Reviews

223

157

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Section: Incompatibilitymentioning

confidence: 99%

Extrachromosomal inheritance in bacteria.

Novick¹

1969

Bacteriological Reviews

223

157

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“…6) If not otherways stated, matings were done as follows. The donor E. coli W3747(Lac+ Strs) and the recipient E. coli W3876 (Lac" Strr) were grown in Penassay broth7) to logarithmic growth phase (1~2 x 108 viable cells per ml).…”

mentioning

confidence: 99%

Polycations which disorganize the outer membrane inhibit conjugation in Escherichia coli.

Viljanen

1987

J. Antibiot.

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Outer membrane disorganizing polycation, polymyxin B nonapeptide (PMBN), reduced drastically the production of recombinants when present at sub-MIC concentrations during F'-mediated Escherichia coli conjugation. The decrease of recombinants was accompanied by a less marked decrease of viability in the recipient population in a manner resembling lethal zygosis. Noreduction was seen wheneither donor or recipient was grownin the same PMBNconcentration, washed and resuspended to PMBN-free medium before mating. The same concentration of outer membrane disorganizing polycations of higher bactericidal activity (protamine and polylysine) caused only a moderate reduction in transconjugant frequency whenpresent during mating. Spermine and tetralysine, which are not effective disorganizers of the outer membrane, did not reduce the recombinant frequency or the viability of the recipients.Conjugation is a natural recombination process of enteric bacteria including Escherichia coli. The best characterized conjugation system is F-plasmid-mediated conjugation in E. coli (reviews1»2)). Cells carrying the F-plasmid can initiate DNAtransfer only when the tra (transfer) cistrons of the plasmid are transcribed and translated to Tra proteins. Most of the 19 known Tra proteins are associated with the cell envelope; seven of them have been localized in the outer membrane(OM), and two found both the inner and outer membranefractions.2) Polycations, like polymyxin B and its derivative polymyxin B nonapeptide (PMBN), cause disorganization of OMseen e.g. as an increased hydrophobic permeability.3»4) It seemed therefore of interest to investigate their possible effects on conjugation.Exp erimenta l The conjugations were carried out in broth between E. coli W3747F13 met" 5) which carries the F'-plasmid F13 determining lactose fermentation (Lac+), and the Lac" E. coli W3876sfaZ lac~rpsL.6)If not otherways stated, matings were done as follows. The donor E. coli W3747(Lac+ Strs) and the recipient E. coli W3876 (Lac" Strr) were grown in Penassay broth7) to logarithmic growth phase (1~2 x 108 viable cells per ml). One ml of both cultures were then mixed and the mating was allowed to continue for 30 minutes at 37°C without shaking. The matings were stopped by vortexing with the highest speed for 10 seconds, and Lac+ recombinants were then selected by plating appropriate dilutions on EM(eosine-methylene blue) minimal medium plates containing lactose and streptomycin.8) The recombinant frequencies are given as the numberof Lac+recombinants/numberof donor cells in the mating mixture before conjugation. PMBNwas prepared from polymyxin B sulfate as described earlier.9) Protamine chloride (from salmon sperm, grade V), spermine hydrochloride, poly-L-lysine hydrobromide (type II ; degree of polymerization 20), and tetralysine hydrochloride were from Sigma (St. Louis, Mo., U.S.A.).

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“…This phenomenon is distinct from the high frequency of recombinants for met, reported by Sugino & Hirota (1962), when R factors bring about conjugation in the Richter y3 strains. The Q3 strain, though losing ability to conjugate, nevertheless retained the chromosomal origin near met characteristic of its parent Hfr strain (Richter, 1961) ; thus, when conjugation factors are introduced which restore its donor ability, recombinants for met are produced at high frequency. The same thing is observed when ' F-refractory ' Hfr strains (Lederberg & Lederberg, 1956) are infected with R factors (Hirota, Fujii & Nishimura, 1966).…”

Section: Discussionmentioning

confidence: 99%