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[the effect of plasmids on the resistance of e. coli to phages].the introduction of the colv, i-k94 or r124 plasmid into escherichia coli k12 resulted in resistance to certain phages. derivatives of e. coli carrying the plasmid r124 and colv, i-k94 were resistance to the phages t4, mel comparing with the plasmid-free parent and the plasmid colv, i-k94 conferred resistance to the phage tull*. it suggested that an envelope change caused by the plasmids might be responsible for the resistance because most of the phages fell to absorb to the plasmid-bearing e. c ...19921299034
distribution of plasmid maintenance regions among incfiv plasmids.the distribution of the incfi basic replicons among incfiv plasmids was assessed by dna hybridization. in addition these and 20 other plasmids from 16 incompatibility groups were screened for the presence of inciv, an incompatibility determinant recently found on the incfiv plasmid r124. the inciv determinant was found commonly but not universally among the incfiv plasmids. it was also detected on the incfi reference plasmid r386 and plasmids from incb, inci alpha and inci gamma. the frequency a ...19892653956
a restriction map of incfiv plasmid r124.a physical and genetic map of the 125.7-kb incfiv plasmid r124 was constructed using the restriction enzymes sal1 and ecor1. two discrete regions involved in plasmid replication were identified on the plasmid genome. one region was located on a 4.66-kb segment of an ecor1 fragment at map coordinates 73.87 to 78.53 kb. another was located within an 8.05-kb segment of an ecor1 fragment at map coordinates 113.40 to 121.45. this region was very unstable but, when ligated to the 3.21-kb ecor1 fragmen ...19853006106
virulence plasmid-associated sensitivity to acid in escherichia coli and its possible significance in human infections.several strains of escherichia coli were markedly sensitised to killing at ph 2.5 or 3.5 when the colv,i-k94 virulence plasmid was introduced into them. for strain 1829, the effect on acid sensitivity was due to the presence of plasmid in the previously resistant strain rather than to its introduction into an acid-sensitive variant already in the population. acid sensitivity was also conferred by the colv-k30 and colb-k98 plasmids and the resistance plasmid r124-f2; other plasmids tested had no ...19863534274
[bacteriophage p22 h5 transfection and infection of plasmid salmonella strains].the results of the ca2+-dependent transfection of the dna of bacteriophage p22 h5 to constructed salmonella typhimurium f'- and r+-strains lt2 wt-r and sa118 demonstrated that in these salmonellae the effectiveness of transfection depended on the specificity of the interrelation of plasmids with host strains. plasmids ra1, r538-1 and rp1 stimulated the transfection of s. typhimurium strain lt2 wt-r, but suppressed the transfection ability of s. typhimurium strain sa118. at the same time the expr ...19836356720
ecor124i: from plasmid-encoded restriction-modification system to nanodevice.summary: plasmid r124 was first described in 1972 as being a new member of incompatibility group incfiv, yet early physical investigations of plasmid dna showed that this type of classification was more complex than first imagined. throughout the history of the study of this plasmid, there have been many unexpected observations. therefore, in this review, we describe the history of our understanding of this plasmid and the type i restriction-modification (r-m) system that it encodes, which will ...200818535150
characterization of the maintenance functions of incfiv plasmid r124.the genetic arrangement of the regions involved in r124 replication and incompatibility have been located and their homology to the incfi basic replicons has been assessed. we show that r124 has homology with all three basic replicons, repfia, repfib, and repfic, and that these regions, fiva, repfivb, and repfivc, are widely separated on the r124 genome. cloning of autonomously replicating fragments has shown that repfivb and repfivc are functional in r124 and express incompatibility. the fiva r ...19873039556
the ecor124 and ecor124/3 restriction and modification systems: cloning the genes.the escherichia coli plasmid r124 codes for a type i restriction and modification system ecor124 and carries genetic information, most probably in the form of a "silent copy," for the expression of a different r-m specificity r124/3. characteristic dna rearrangements have been shown to accompany the switch in specificity from r124 to r124/3 and vice versa. we have cloned a 14.2-kb hindiii fragment from r124 and shown that it contains the hsdr, hsdm, and hsds genes which code for the ecor124 r-m ...19853006102
the escherichia coli prr region encodes a functional type ic dna restriction system closely integrated with an anticodon nuclease gene.the prr locus was originally described as coding a ribonuclease that is activated after phage t4 infection to cut within the anticodon of a specific trna, inactivating protein synthesis and thus blocking phage development. wild-type t4 phage has two genes coding the enzymes polynucleotide kinase and rna ligase, whose only function seems to be to repair the damage done by the anticodon nuclease. as the only apparent function of the prr ribonuclease is to combat phage infection, it can be consider ...19948145241
restriction endonucleases r.ecoki and r.ecor124i are probably located in different environments within the bacterial cell.we describe the phenomenon of a transient state of r124i restriction deficiency after long-term storage of the e. coli[pcp1005] strain at 4 degrees c, or after growth of the culture in synthetic m9 medium with the nonmutagenic solvent dimethyl sulfoxide. the unusual high reversion from the r+ 124 to the r- 124 phenotype was observed only in e. coli strain transformed with the high-copy number plasmid pcp1005 carrying ecor124i hsdr, m and s genes cloned, but not with strains carrying the natural ...19947959434
host components required for the replication of the resistance plasmid r124 and a copy mutant derivative.the replication of r124, and a copy mutant derivative of it, was measured with respect to dependence on the host dnaa, dnab, dnac, dnae, dnag, and pola gene products. both plasmids replicated under conditions where the dnaa gene product was inactivated or where the polymerising activity of the pola gene product was reduced. in contrast, neither plasmid replicated to any appreciable extent, if the dnab, dnac, dnae or dnag gene products were inactivated. r124 integratively suppressed the lesion of ...19806990641
effects of the resistance plasmid r124 on the level of the ompf outer membrane protein and on the response of escherichia coli to environmental agents.the introduction of the f-like resistance plasmid r124 into an ompc mutant of escherichia coli k12 conferred altered sensitivity to a wide range of inhibitory agents. sensitivity to ampicillin, chloramphenicol, ethionine, copper ions, deoxycholate, two fatty acids and colicins l and m was decreased by the plasmid. in contrast the plasmid-bearing ompc derivatives were more sensitive than the plasmid-free ompc mutant to erythromycin, cetyltrimethylammonium bromide and phenol. introduction of r124 ...19846368513
incompatibility properties of the incfiii/fiv haemolytic plasmid psu316 when integrated in the escherichia coli chromosome.the haemolytic plasmid psu316 is incompatible with members of the incfiii and incfiv incompatibility groups. plasmid psu307 (psu316 hlyc::tn5) was inserted by integrative suppression into the chromosome of jw112, a temperature-sensitive dnaa mutant of escherichia coli. the incompatibility properties of this strain (su51) were studied and it was found that: (1) plasmid psu306 (psu316 hlya::tn802) was rapidly lost from strain su51 both at 30 degrees c and 42 degrees c; (2) the incfiii plasmid psu3 ...19836313856
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