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At least 19 recordsLinked to original sources
PubMed1978

Deletion plasmids from transformants of Pseudomonas aeruginosa trp cells with the RSF1010-trp hybrid plasmid and high levels of enzyme activity from the gene on the plasmid.

A RSF1010-trp hybrid plasmid which contained the tryptophan operon of Escherichia coli was introduced into Pseudomonas aeruginosa trp cells by transformation. From the Trp+ transformants several deletion plasmids were obtained, and their physical maps with restriction endonucleases were constructed. P. aeruginosa trp cells with these plasmids showed at first more than 100 times higher levels of tryptophan synthetase beta activity over that of the control P. aeruginosa wild-type cells, but these levels were drastically decreased by 1 week of successive transfers of cultures. This decrease in enzyme activity was found to be due to the change on the plasmids but not to the host cells. The production of E. coli tryptophan synthetase beta enzyme in P. aeruginosa cells was proved by immunological test.

Anthranilate Synthase↗
PubMed1992

Plasmid profiles of Acinetobacter and Enterobacter species of hospital origin: restriction endonuclease analysis of plasmid DNA and transformation of Escherichia coli by R plasmids.

A total of 37 multi-resistant strains (20 Acinetobacter calcoaceticus and 17 Enterobacter cloacae) were isolated from patients of the Intensive Care Units. All the isolates were examined for resistance to a battery of antimicrobial agents by the disk diffusion method. Plasmid profiles and restriction endonuclease analysis of plasmid DNA by EcoR1 revealed the spread of one A. calcoaceticus and two E. cloacae endemic strains. Transformation experiments on Escherichia coli competent cells by three plasmids established the presence of R plasmids in the multi-resistant isolates.

Acinetobacter↗
PubMed1976

Plasmids controlling synthesis of hemolysin in Escherichia coli. II. Polynucleotide sequence relationship among hemolytic plasmids.

Plasmids of three different sizes, designated as plasmid A (mw: 65 X 10(6), plasmid B (mw: 41 X 10(6) and plasmid C (mw: 32 X 10(6) respectively, have been isolated from various hemolytic wild-type strains of E. coli. DNA-DNA hybridization was performed to determine their relationship. The wild-type strain, PM167a, harbours plasmids of all three sizes. Hybridization studies indicate that all three plasmids share extented sequence homologies but that plasmid A is not composed of plasmids B and C. Hybridization between plasmids of the donor strain and those of appropriate transconjugants demonstrates that in some cases plasmids with identical size are not longer completely homologous in their nucleotide sequences. This indicates that despite their defined sizes these plasmids are not stable genetic entities, but rather they undergo frequently recombination and dissociation during conjugation. In one particular transconjugant strain, K12-PM152/1, a plasmid D was found which is a stable recombined molecule of plasmids B and C of the original strain. Plasmids of size B found as the only extrachromosomal elements in a hemolytic wild-type strain (P224) and two transconjugant strains (e.g. K12-CM20 and K12-PM167/1) share extended nucleotide sequence homologies but are not identical. Little sequence homology was observed between two different hemolytic plasmids and the F and the Col Ib plasmids suggesting that the former do not belong to either the F-like or the I-like group of plasmids. Another hemolytic plasmid is F-like based on its sequence homologies with the F factor.

Base Sequence↗
PubMed1977

Differential association of F' plasmid and R plasmid deoxyribonucleic acid with a rapidly sedimenting fraction of a Proteus mirabilis lysate.

We have examined the association of an F' plasmid and an R plasmid in Proteus mirabilis with a rapidly sedimenting material that is generated by sodium dodecyl sulfate lysis and low speed centrifugation. Virtually all of the chromosomal deoxyribonucleic acid (DNA) and the F' plasmid DNA are associated with the rapidly sedimenting material after gentle lysis and centrifugation. A portion of R plasmid NR1 DNA (usually 5 to 25%) is not bound to the rapidly sedimenting material and is recovered in the supernatant fraction. This difference in binding is not related to the size of the plasmid DNA, since F' plasmids and R plasmids of different molecular weights showed the same behavior. R plasmid DNA labeled by a brief pulse of [(3)H]thymine is recovered in the supernatant fraction to a lower extent than the total R plasmid DNA. It would appear that R plasmid replication takes place in association with the rapidly sedimenting material. With prolongation of the [(3)H]thymine pulse, the [(3)H]thymine-labeled R plasmid DNA is recovered in the supernatant fraction with the same probability as the total R plasmid DNA. This finding indicates that a change in R plasmid attachment to the rapidly sedimenting material occurs some time after its replication. The differences observed in the replication of F' plasmids and R plasmids in P. mirabilis may be related to their different modes of association with the rapidly sedimenting material.

Bacteriolysis↗
PubMed1975

Recombinant plasmid obtained from two different, compatible staphylococcal plasmids.

From two different, compatible staphylococcal plasmids that determine streptomycin and chloramphenicol resistance, respectively, a recombinant plasmid was obtained. This plasmid can be transduced with a rather high frequency (10(-4)/plaque-forming unit) to plasmid-negative strains, the linkage of the two markers being 100%. The maintenance of the recombinant plasmid in the host cell seems to be controlled by the chloramphenicol resistance plasmid. The recombinant plasmid proved to be incompatible with both parental plasmids, which are unrelated. The relationship between the chloramphenicol resistance plasmid and the recombinant plasmid was the same as the between genetically marked derivatives of the recombinant plasmid, whereas the relationship of the streptomycin resistance plasmid to the recombinant plasmid was of a different, asymmetrical type.

Chloramphenicol↗
PubMed1977

[Incidence and mobility of R plasmids, Col plasmids and Hly plasmids in E. coli isolated from healthy calves and calves with diarrhea].

Within the set of 200 strains of E. coli isolated from healthy calves and 60 strains of E. coli isolated from calves suffering from diarrhoea we compared the incidence and transfer of determinants of antibioticoresistance, colicinogenesis and hemolytical activity. A significant difference in the incidence and independent mobility of the agents under examination in favour of E. coli from calves suffering from diarrhoea was determined in the case of resistance to chloramphenicol. The increased incidence and independent mobility of the chloramphenicol element in the antibioticoresistent strains of E. coli isolated from calves suffering from diarrhoea can be explained by the three to five-day therapy with a chloramphenicol product.

Animals↗
PubMed1976

Plasmids in Streptococcus lactis: evidence that lactose metabolism and proteinase activity are plasmid linked.

Populations of lactose positive (Lac+) and proteinase positive (Prt+) cells from Streptococcus lactis M18, C10, and ML3 grown at 39 degrees C gave rise to increasing proportions of Lac- Prt- clones. The deficiencies did not appear until after a number of generations at the elevated temperature, and the rate depended on the strain.Lac- Prt+ and Lac+ Prt- mutants were isolated after treatment with ethidium bromide. Plasmid deoxyribonucleic acid was isolated by cesium chloride-ethidium bromide equilibrium density gradient centrifugation from the parent cultures as well as from their Lac- Prt-, Lac- Prt+, and Lac+ Prt- mutants. Five distinct plasmid sizes of approximate molecular weights of 2,4, 8, 21, and 27 million were found in S. lactis C10, whereas the Lac- Prt- derivative lacked the 8- and 21-million-dalton plasmids, but the 8-million-dalton plasmid was present in the Lac-Att mutant. In S. lactis m18 five plasmids possessing molecular weights of about 2, 4, 10, 18 and 27 million were observed. The 10- and 18-million-dalton plasmids were not detected in the Lac- Prt- mutants, whereas the Lac- Prt+ derivative lacked only the 18-million-dalton plasmid and the Lac+ Prt- mutant lacked only the 10-million-dalton plasmid. In S. lactis ML3 five distinct plasmids, with approximate molecular weights of 2, 4, 8, 22, and 30 million, were present. The 8- and 22-million-dalton plasmids were not detected in the Lac- Prt- derivative, but the 8-million-dalton plasmid was present in the Lac- Prt+ mutant. The evidence suggests that lactose-fermenting ability and proteinase activity in these organisms are mediated through two distinct plasmids having molecular weights of 8 x 10(6) to 10 x 10(6) for proteinase activity and 18 x 10(6) to 22 x 10(6) for lactose metabolism.

DNA, Bacterial↗
PubMed1992

Plasmid instabilities of single and three-plasmid systems in Escherichia coli during continuous cultivation.

Plasmid instabilities in E. coli JM103 carrying three plasmids (pRK248cI, pMTC48, pEcoR4) and a single plasmid system (pTG206) for the production of fusion EcoRI (SPA::EcoRI) and catechol 2,3-dioxygenase, respectively, were investigated in continuous cultures under selective and non-selective conditions. In a three-plasmid system, pRK248cI was lost gradually together with pMTC48 from the host under non-selective conditions. The selective pressure against pRK248cI stabilized the pMTC48. This indicates that the loss of pMTC48 under non-selective conditions was caused by the loss of cI857 gene (coded by pRK248cI) which resulted in the overproduction of the toxic gene product (coded by pMTC48). In the case of single plasmid (pTG206) system, the plasmid lost from the host under non-selective conditions. This plasmid was stabilized in the host growing under selective conditions. During this period we obtained some ampicillin resistant colonies which gave low levels of enzyme activities compared to the normal plasmid bearing cells. Plasmid analysis from the above cells showed that the plasmid has undergone structural instability. Further, restriction analysis of this plasmid exhibited an additional PvuII site in a 0.9 kbp fragment that was integrated near the tet promoter which controls the expression of the xyl E gene, thereby resulting low levels of enzyme activities. Our results indicate that some of the IS elements which are present in the host chromosome were responsible for such instabilities to turn off the synthesis by inserting into the tet promoter region to lower the protein formation during the bioprocess.

Base Sequence↗
PubMed1977

Apparent fusion of the TOL plasmid with the R91 drug resistance plasmid in Pseudomonas aeruginosa.

The TOL catabolic plasmid was shown to be compatible with the R91 drug resistance plasmid. However, the TOL plasmid was extremely unstable in mutant PA03 of P. aeruginosa. By selecting for stabilization of the TOL plasmid in PA03 harbouring R91, it was possible to isolate a strain in which markers from both R91 and TOL appeared to exist in a single recombinant plasmid. This plasmid, pND3, encoded resistance to carbenicillin, was able to transfer at the same frequency as the R91 plasmid and encoded the ability to grow on m-toluate, p-toluate, m-xylene, p-xylene and toluene. In addition, it was shown to be incompatible with the NAH catabolic plasmid and it could be transferred by transduction. The TOL plasmid could stabilize in PA03 harbouring R91 without fusion with R91, and could stabilize in PA03 in the absence of R91. PA03 harbouring either the recombinant plasmid or the stable TOL plasmid in the absence of R91 could promote bacterial chromosome transfer between mutant derivatives of P. aeruginosa strain PA0.

Mutation↗
PubMed1992

Virulence plasmid pJM1 prevents the conjugal entry of plasmid DNA into the marine fish pathogen Vibrio anguillarum 775.

Studies involving the introduction of cloned homologous genes into Vibrio anguillarum revealed that several plasmids could not be conjugally introduced into V. anguillarum 775(pJM1), but were transmissible to the pJM1-cured derivative H775-3. Recombinant pBR322 plasmids containing V. anguillarum genomic DNA inserts were mobilized from Escherichia coli donors, using pRK2013, into V. anguillarum H775-3 recipients at frequencies of 10(-6) to 10(-5) per recipient. When identical matings were performed with V. anguillarum 775(pJM1) recipients, the infrequent exconjugants recovered carried the pBR322-based plasmid but had lost the large virulence plasmid pJM1. Similar studies were carried out with plasmid RP4 and with recombinant derivatives of the closely related broad-host-range plasmid pRK290. While RP4 was transmissible from E. coli to V. anguillarum H775-3 at frequencies of 6.7 x 10(-2) per recipient, transmission to V. anguillarum 775(pJM1) recipients occurred at frequencies of only 2.5 x 10(-7). When pRK290 contained V. anguillarum DNA inserts, the only exconjugants recovered had lost pJM1, or contained pJM1 and a deletion derivative of the recombinant pRK290 plasmid where all of the DNA insert had been deleted. The use of Dam-, Dcm-, or EcoK- methylation-deficient E. coli donor strains failed to result in appreciable numbers of V. anguillarum 775(pJM1) exconjugants that contained the desired transferred plasmids. Following UV mutagenesis, a derivative of V. anguillarum 775(pJM1) was isolated that would accept conjugally transferred plasmid DNAs at frequencies similar to those observed when using V. anguillarum H775-3 recipients. These data suggest that virulence plasmid pJM1 mediates a restriction system that prevents conjugal transmission of plasmid DNA from E. coli donors into V. anguillarum 775(pJM1). This putative restriction system appears not to be directed towards Dam-, Dcm-, or EcoK-methylated DNA, and appears not to involve a Type II restriction endonuclease.

Animals↗
PubMed1992

Macroevolution of plasmids: a model for plasmid speciation.

A new evolutionary model for diversification in plasmid incompatibility groups (plasmid speciation) is suggested. The model is based on the formation of plasmid cointegrates from two compatible plasmids. The existence of plasmid cointegrates is well known, however, their potential key role in plasmid macroevolution has not yet been recognized. In a hypothesis presented here, one of the rep genes is supposed to be relaxed from selection in plasmid cointegrates and thus becomes free to accumulate mutations. These mutations can lead to a change in incompatibility specificity. Evidence supporting this hypothesis comes from the common occurrence of multi-replicon plasmids in nature as well as from experimental studies on plasmid cointegrate formation. A more speculative extension of this model hypothesizes an evolutionary scenario for origin of the eubacterial single-replicon genome and the eukaryotic multi-replicon genome, as well as the place of plasmids and viruses in this picture.

Bacteria↗
PubMed1977

Physical characterization of a plasmid cointegrate containing an F'his gnd element and the Salmonella typhimurium LT2 cryptic plasmid.

A recombinant plasmid (pAS19) isolated from a derivative of Salmonella typhimurium LT2, containing the strain LT2 cryptic plasmid and an F'his gnd element, has been physically characterized. The pAS19 plasmid contour length equals the sum of the contour lengths of the cryptic plasmid and F'his gnd element. Deoxyribonucleic acid (DNA)-DNA hybridization experiments demonstrated that whereas the pAS19 plasmid exhibits extensive DNA homology with both the cryptic plasmid and the F'his gnd element, there is little DNA homology between these latter two plasmids. The DNA fragmentation pattern of the pAS19 plasmid produced by the restriction endonuclease R-EcoRI is consistent with that expected for a composite plasmid cointegrate containing most, if not all, of the DNA sequences present in its two component plasmids.

Animals↗
PubMed1979

[Genetic control of the formation of plasmid F'. I. Effect of recA- and seg-2 mutations in an Hfr donor strain on the character of plasmid F' formation].

Assuming the similarity of the processes of illegitimate recombination, such as deletion formation, with the process of F' plasmid formation, we have undertaken the study of the influence of recA- and seg- alleles of Hfr donor on the F' plasmid formation. The data obtained demonstrate the strong influence of donor genotype on the frequency of F' plasmid formation and on the nature of F' plasmids formed, thus demonstrating that the most of F' plasmids have been formed via recombination in Hfr donor cells. The recA- mutation decreased the total yield of F' plasmids selected using both proximal and distal Hfr markers and affected drastically the distribution of the F' plasmids inheriting different proximal unselected markers. The existence of recA-dependent and recA-independent modes of F' plasmid formation was demonstrated. The Escherichia coli chromosome contains regions which involve preferentially in recA-dependent (between proA and gal, and clockwise from gal) or recA-independent (between leu and proA, and the region counterclockwise from argE) recombination. The seg-2 mutation causes only partial block of both recA-dependent and recA-independent recombination pathways, however it causes dramatic decrease of genetic exchanges leading to the formation of the type II F' plasmids. Both seg- and recA- mutations decrease the frequency of the formation of Tra+ F' transconjugants. The percent of Tra- transconjugants, which remain sensitive to MS2 and Q beta donor specific phages, also drops significantly under the influence of the recA- and seg- alleles. Thus, the recombination involving the F structure in wild type strains and seg- mutants occures preferentially in the points of F outside the regions essential for transfer and sensitivity to male specific phages, while in recA- and recA-ges- strains the points inside these regions (tra operon) frequently involved in F' plasmid looping out. There exist more strict correlation between the fertility and sensitivity to phage Q beta than to phage MS2.

Chromosome Deletion↗
PubMed1978

Isolation of large bacterial plasmids and characterization of the P2 incompatibility group plasmids pMG1 and pMG5.

Large plasmids from Agrobacterium tumefaciens, Salmonella typhimurium, Escherichia coli, Pseudomonas putida, and Pseudomonas aeruginosa were routinely and consistently isolated using a procedure which does not require ultracentrifugation but includes steps designed to separate large-plasmid DNA from the bacterial folded chromosome. It also selectively removes fragments of broken chromosome. A variety of large plasmids was readily visualized with agarose gel electorphoresis, including five between 70 and 85 megadaltons (Mdal) in size, six between 90 and 143 Mdal, one that was larger than 200 Mdal, and one that was larger than 300 Mdal. This isolation procedure allowed initial estimation of the molecular sizes of the two IncP2 plasmids, pMG1 and pMG5, which were 312 and 280 Mdal, respectively. A standard curve for size determination by gel electrophoresis including plasmids between 23 and 143 Mdal in size did not extrapolate linearly for plasmids of the 300-Mdal size range. Unique response of different plasmids to the isolation procedure included sensitivity of IncP1 plasmids to high pH and the co-isolation of a 20-Mdal "cryptic" plasmid in conjunction.

DNA, Bacterial↗
PubMed1979

[Mechanism of plasmid ColEl and pMB-9 mobilization by plasmid F'lac+ in Escherichia coli K-12].

The genetic control and mechanism of mobilization of the non-conjugative plasmids ColE1 and pMB-9 by the conjugative plasmids was orived to be recA-independent process in contrast to the mobilization of the chromosomal marker pro. Acridine orange and ethidium bromide curing data together with the results of electrophoretic analysis of plasmid DNA suggest that the plasmids F' lac+ and pMB-9 as well as F' lac+ and ColE1 remain autonomous after their contransfer to recipient cells. These data argue in favour of non-recombinational nature of the plasmid mobilization process. The possibility of transmission of a non-conjugative plasmid without transmission of a conjugative one from the donor strain carrying both plasmids was established. The results obtained are discussed with respect to the hypothesis on the effect of diffusible products encoded by the conjugative plasmid and required of the mobilization of the non-conjugative plasmid.

Conjugation, Genetic↗
PubMed1976

Genetic and physical studies of recombinant plasmids formed between an R plasmid of compatibility group FI and sex factor F of HfrH.

Recombinant plasmids between an R plasmid of the FI group (R162/3) and the sex factor F or HfrH were produced after the conjugal transfer of this R plasmid into HfrH. Three types of recombinant plasmids were identified after the mating of HfrH (R162/3) with recA and rec+ recipients. One specimen of each type (pIP218, pIP222, pIP226) was studied in this report. All three recombinant plasmids carry the same genetic information for resistance to antibiotics (CSSuT) retained from R162/3. pIP218 retained all the other properties from F of HfrH: derepression for pilus synthesis, mobilization of the chromosome for the proximally transferred HfrH genes (thr, leu, proA), interference with T7 propagation, and ability to be cured by acridine orange. pIP222 retained from F of HfrH the derepression for pilus synthesis and the same polarity of chromosome transfer (thr, leu, proA), while pIP226 retained the interference with T7 propagation and acridine orange curing. Physical studies revealed that replication control and/or recovery of F and pIP218 as covalent circles of deoxyribonucleic acid are similar, and are different from R162/3. The new plasmids are more likely the result of a substitutive recombination event than a fusion. We propose genetic maps of these recombinant plasmids, showing the unequal participation of the parental plasmids in their formation.

Acridines↗
PubMed1978

Genetic properties of the Salmonella enteritidis R404 plasmid aggregate. II. Separation of plasmids by transformation.

Transformational separation of plasmids from R404 plasmid aggregate found in Salmonella enteritidis strain was performed. Three classes of transformants differing in their resistance patterns were isolated. Genetic properties of the transformants suggest that their resistance is determined by single plasmids. Plasmid pCK3 (Tra-ApCbCrSuSm) and pCK4 (Tra-ApCbCrCm) are nonconjugative while plasmid pCG1 (TraApCbCrSuSmTcKmNm) is conjugative. Separation of all plasmids of R404 plasmid aggregate allowed to determine their genetic properties and the manner of conjugational transfer of R404 plasmid aggregate R-determinants.

Anti-Bacterial Agents↗