| [new indications for the participation of group p plasmids r in the transfer of chromosomal genes in intergenera crosses]. | use of e. coli strains with phenotypes rec+ and rec- asrecipients in intergenera crosses confirmed the supposition put forward by the authors formerly that new chromosomal markers in transconjugantes originated due to psuedomonas aeruginosa. these chromosomal markers were transferred together with plasmid r conditioning the conjugation, and maintained without being built-into e. coli chromosome. between the arg+ marker and the plasmid r18 there existed labile physical connection demonstrable onl ... | 1978 | 106604 |
| characterization of a nosocomially significant, multiple drug-resistant strain of serratia marcescens. | a multiple drug-resistant strain of serratia marcescens (bacteriocin type 18) was isolated from three clinical patients. the isolates were found to carry a conjugally nontransferable, nonmobilizeable resistance plasmid (r-plasmid) with resistance-(r)-determinants against ten antimicrobial drugs: ampicillin, carbenicillin, chloramphenicol, gentamicin, kanamycin, neomycin, streptomycin, tobramycin, triple sulfonamides, cotrimoxazole, and--possibly--nalidixic acid, as determined with exposure to 'c ... | 1976 | 181215 |
| reversal of sodium-azide mutagenicity by liver preparations and by gastric juice. | sodium azide was found to be mutagenic for salmonella typhimurium by inducing base-pair substitutions that were not enhanced by pkm101 plasmid (r factor). however, the mutagenicity of sodium azide was decreased by enzyme proteins contained in rat-liver post-mitochondrial fractions, depending on the nadph-generating system. pre-incubation with human gastric juice also decreased azide mutagenicity. these metabolic effects might explain the conflicting nature of the mutagenicity and carcinogenicity ... | 1979 | 384225 |
| [extrachromosomal antibiotic resistance of the intestinal bacterial flora. ii. the role of resistance acquired by endogenous intestinal bacterial flora (author's transl)]. | in a previous paper, we have shown that multiple resistant bacteria in the human gut flora may have two origins: firstly, through food which carries resistant bacteria and secondly, our present study, resident intestinal bacteria which become resistant to antibiotics, either because they are chromosomic mutant or because they acquire resistance plasmid from an exogen strain. in all cases these resistant bacteria can implant and multiply in the gut only if there are disorders in the normal bacter ... | 1977 | 593869 |
| expression of the plasmid pkm101--determined dna repair system in reca- and lex- strains of escherichia coli. | pkm101, a plasmid r factor of the n compatibility group increases methylmethane sulfonate mutagenesis and diminishes uv-killing in reca+ lex+ and reca+ lex- strains, , but not in reca-lex+ strains. the induction of a "reclex" dependent colicin is not present in lex- strains carrying the pkm101 factor. these facts indicate that pkm101 acts through an error-prone dna repair system which is reca+ dependent, but not lex+ dependent. | 1976 | 781517 |
| [transformation of bacillus subtilis by isolated plasmid r dna]. | | 1976 | 816627 |
| two replication initiation sites on r-plasmid dna. | replicating dna molecules of a deletion mutant of the conjugative r-plasmid r 6 k are cleaved at a single site by the ecori restriction endonuclease. electron microscope examination and measurements of the ecori treated replicative intermediate molecules indicate that replication can be initiated at two sites on the plasmid dna molecule. the two sites are located at about 23 and 39% of total length, respectively, from the ecori cleavage site. about 5% of the replicating molecules use both replic ... | 1975 | 1102950 |
| [mechanism of control of replication of plasmid r ts 1]. | | 1975 | 1240228 |
| methyl methanesulphonate (mms) is clearly mutagenic in s. typhimurium strain ta1535; a comparison with strain ta100. | no mutagenicity or an uncertain mutagenic response has been reported in the literature for methyl methanesulphonate (mms) in s. typhimurium strain ta1535 when using the plate assay. in our studies we found a reproducible mutagenic activity of 62 revertants/mumole and plate for mms in strain ta1535 when using the preincubation assay. a dose-dependent increase in revertants was, however, observed only at fairly high doses (exceeding 4 mumole). two different slopes were observed in the dose-respons ... | 1989 | 2664497 |
| the phototrophic bacterium rhodopseudomonas capsulata sp108 encodes an indigenous class a beta-lactamase. | the nucleotide sequence of a 2.37 kb dna fragment derived from cloning a total dna digest of rhodopseudomonas capsulata sp108 was determined. the dna codes for a beta-lactamase, a protein showing sequence similarity to the ampr protein of enterobacter cloacae and an unidentified open reading frame. hybridization experiments with a probe carrying dna from within the beta-lactamase gene suggests a chromosomal location for the coding sequences in strain sp108 and in sp109, a penicillin-sensitive re ... | 1989 | 2788410 |
| requirement of the escherichia coli dnaa gene function for integrative suppression of dnaa mutations by plasmid r 100-1. | the phenotype of escherichia coli dnaa missense and nonsense mutations was integratively suppressed by plasmid r100-1. the suppressed strains, however, could not survive when the dnaa function was totally inactivated. this was demonstrated by the inability of replacing the dnaa allele in the suppressed strain by a dnaa::tn10 insertion using phage p1-mediated transduction. when the intact dnaa+ allele was additionally supplied by a specialized transducing phage, lambda imm21 dnaa+, which integrat ... | 1988 | 2851703 |
| [cis-active function of plasmid r 57 resolving co-integrates formed during transposition of isi-elements]. | the mechanism of pbr322 plasmid mobilization in the cells of escherichia coli k-12 reca by conjugative factor r57 was studied. it was shown that mobilization of pb322 is achieved by formation of unstable is1-mediated cointegrates with r57. in the rec+ e. coli strains cointegrates resolved with formation of pbr322:is1 plasmids. in the reca bacteria the cointegrates dissociated to pbr:is1, as well as to other insertion derivatives of pbr322. some of the latter contain tn9-like sequence, i.e. a tra ... | 1985 | 2990321 |
| [comparative topography of the catalytic sites of chromosomal dihydrofolate reductases and that of the enzyme encoded in r 67 plasmid from e. coli]. | the trimethoprim-resistant dihydrofolate reductase specified in e. coli by plasmid r 67, when compared, with other enzymes catalyzing the same reaction, to have a dissimilar primary, secondary, tertiary and quaternary structure. in regard to the tertiary structure, we show here that the pteridine binding site, in the plasmid-encoded enzyme, has a geometrical similarity with that of other chromosomal specified reductases. | 1988 | 3136866 |
| replication intermediate of a hybrid plasmid carrying the replication terminus (ter) site of r 6k as revealed by agarose gel electrophoresis. | a 4.32 kb dna fragment, on which the dna replication terminus (terr) site of plasmid r 6k was located, was inserted into the unique ecori site of plasmid puc9. to detect replication intermediate molecules with a replication fork halted at the terr site, a cell dna extract was digested with ecori, electrophoresed through an agarose gel and stained with ethidium bromide. in addition to two major bands, one derived from vector dna and the other from the ter insert fragment, two extra minor bands we ... | 1987 | 3323842 |
| common plasmid encoding resistance to ampicillin, chloramphenicol, gentamicin, and trimethoprim-sulfadiazine in two serotypes of salmonella isolated during an outbreak of equine salmonellosis. | an outbreak of equine salmonellosis occurred at the veterinary medical teaching hospital, university of california, davis, between june 1981 and march 1982. forty-four horses were infected with salmonella saint-paul, a serotype rarely isolated from animals at the university before the outbreak. unlike the isolates of s saint-paul obtained at the beginning of the outbreak, almost all strains isolated near the end were resistant to ampicillin, cephalothin, chloramphenicol, gentamicin, kanamycin, s ... | 1985 | 3848289 |
| effect of rec mutations on the ultraviolet protecting and mutation-enhancing properties of the plasmid r-utrecht in salmonella typhimurium. | | 1973 | 4585477 |
| the nucleotide sequence of the replication control region of the resistance plasmid r1drd-19. | the region of plasmid r 1 containing the replication control genes has been sequenced using the maxam-gilbert method. the nucleotide sequence of two small psti restriction fragments (a total of about 1,000 base pairs) was determined for the wild-type r 1 plasmid as well as for two different copy mutants. it was found that one copy mutant has a single base substitution in the fragment which was recently shown to harbor an important inc/cop gene (molin and nordström 1980). furthermore, the sequenc ... | 1981 | 6261081 |
| [interaction of shigella sonnei phase-i strains carrying f'- or r386 plasmids with continuous hela- and l-line cells]. | the region of s. sonnei chromosome, located to the left of the gene lac i, has been found to be linked with the capacity of these bacteria for penetrating epithelial cells: this capacity is sharply suppressed in transconjugates carrying plasmids f' which cover the above-mentioned chromosomal region in recipients. the loss of virulence by transconjugates with transferred plasmids f'lac is not linked with the transfer of f factor proper, as those transconjugates which have acquired plasmids f' fro ... | 1983 | 6318481 |
| [effect of plasmids for multiple antibiotic resistance on the change in salmonella typhimurium phagovar]. | the data on the influence of acquired plasmid resistance to antibiotics on s. typhimurium phagovar. plasmid r was transferred from s. typhimurium strain, isolated from the focus of hospital salmonellosis and resistant to the lytic action of phages, to escherichia coli k12 and then to antibiotic-sensitive s. typhimurium strains of different phagovars, isolated from patients with alimentary toxicoinfections. the influence of plasmid r on the phagovar of recipient strains, most pronounced in strain ... | 1984 | 6395585 |
| [energy supply for transport of plasmid r 100-1 during conjugation of escherichia coli cells]. | it was shown that the transfer of plasmid r 100-1 during conjugation of donor and recipient cells of e. coli is suppressed under treatment of the cells by oxidative phosphorylation uncouplers. studies on recipient cells devoid of their h+-atpase activity due to mutation showed that the transfer of the plasmid into the cells is repressed after a switch-off of the respiratory chain, the only generator of proton motive force in the mutated cells. in the absence of arsenate the plasmid transfer from ... | 1980 | 6452175 |
| [plasmid r-determined variability of bacteria. ii. effect of conjugational properties of plasmids r on the variability of bacteria]. | | 1980 | 6992128 |
| dna sequence of a plasmid-encoded dihydrofolate reductase. | the sequence of the methotrexate-resistant dihydrofolate reductase (dhfr) gene borne by the plasmid r-388 was determined. the gene was subcloned and mapped by an in vitro mutagenesis method involving insertion of synthetic oligonucleotide decamers encoding the bamhi recognition site. sites of insertion that destroyed the methotrexate resistance fell in two regions separated by 300 bp within a 1.2 kb fragment. one of these regions encodes a 78 amino acid polypeptide homologous to another drug-res ... | 1981 | 7022127 |
| in vitro assembly of an anion-stimulated atpase from peptide fragments. | the oxyanion-translocating atpase encoded by the ars operon of plasmid r 773 confers resistance to antimonials and arsenicals in escherichia coli by extrusion of the oxyanions from the cells. the catalytic subunit, the arsa protein, is an oxyanion-stimulated atpase with two nucleotide binding consensus sequences, one in the n-terminal half and one in the c-terminal half of the protein. in this report subclones of the arsa gene were constructed to produce polypeptide fragments of the arsa protein ... | 1994 | 8144560 |
| [ampicillin resistance mediated by the r plasmid in strains of shigella flexneri]. | forty shigella flexneri strains isolated from children attended to at the children's hospital of camagüey during an outbreak of acute diarrheal disease were studied; the minimal inhibitory concentration of ampicillin was determined. 33 strains (82.5%) were resistant to higher concentrations: 8 to 16 micrograms/ml, and 7 were susceptible to 4 micrograms/ml concentrations. resistance plasmid (r) extraction was carried out in all the isolated strains and a common plasmid was found this plasmid was ... | 1994 | 9768253 |
| inhibition by epigallocatechin gallate (egcg) of conjugative r plasmid transfer in escherichia coli. | epigallocatechin gallate (egcg) in tea catechins blocked or significantly diminished the transfer of conjugative r plasmid between escherichia coli c600 with plasmid r-222 (donor) and e. coli k-12 rc85 (recipient) in a dose-dependent manner. the inhibition rates of r plasmid transfer by egcg were 42%-67% at 50-200 microg/ml, and up to 99% at 800 microg/ml. nevertheless, egcg, even at the concentration of 1600 microg/ml, was not sufficient to kill e. coli cells in 1 h, as confirmed by determining ... | 2001 | 11810584 |
| new restriction enzymes discovered from escherichia coli clinical strains using a plasmid transformation method. | the presence of restriction enzymes in bacterial cells has been predicted by either classical phage restriction-modification (r-m) tests, direct in vitro enzyme assays or more recently from bacterial genome sequence analysis. we have applied phage r-m test principles to the transformation of plasmid dna and established a plasmid r-m test. to validate this test, six plasmids that contain bamhi fragments of phage lambda dna were constructed and transformed into escherichia coli strains containing ... | 2003 | 12595571 |
| host factor titration by chromosomal r-loops as a mechanism for runaway plasmid replication in transcription termination-defective mutants of escherichia coli. | two escherichia coli genes, rnha and recg, encode products that disrupt r-loops by hydrolysis and unwinding, respectively. it is known that the propensity for r-loop formation in vivo is increased during growth at 21 degrees c. we have identified several links between rnha, recg, and r-loop-dependent plasmid replication on the one hand, and genes rho and nusg involved in factor-dependent transcription termination on the other. a novel nusg-g146d mutation phenocopied a rho-a243e mutation in confe ... | 2003 | 12946345 |
| comparison of two major forms of the shigella virulence plasmid pinv: positive selection is a major force driving the divergence. | all shigella and enteroinvasive escherichia coli (eiec) strains carry a 230-kb virulence plasmid (pinv) which is essential for their invasiveness. there are two sequence forms, pinv a and pinv b, of the plasmid (r. lan, b. lumb, d. ryan, and p. r. reeves, infect. immun. 69:6303-6309, 2001), and the recently sequenced pinv plasmid from shigella flexneri serotype 5 is a pinv b form. in this study we sequenced the majority of the coding region of the pinv a form from s. flexneri serotype 6 other th ... | 2003 | 14573649 |
| kpnbi is the prototype of a new family (ie) of bacterial type i restriction-modification system. | kpnbi is a restriction-modification (r-m) system recognized in the gm236 strain of klebsiella pneumoniae. here, the kpnbi modification genes were cloned into a plasmid using a modification expression screening method. the modification genes that consist of both hsdm (2631 bp) and hsds (1344 bp) genes were identified on an 8.2 kb ecori chromosomal fragment. these two genes overlap by one base and share the same promoter located upstream of the hsdm gene. using recently developed plasmid r-m tests ... | 2004 | 15475385 |
| conservation of recg activity from pathogens to hyperthermophiles. | maintaining the integrity of the genome is essential for the survival of all organisms. recg helicase plays an important part in this process in escherichia coli, promoting recombination and dna repair, and providing ways to rescue stalled replication forks by way of a holliday junction intermediate. we purified recg proteins from three other species: two gram-positive mesophiles, bacillus subtilis and streptococcus pneumoniae, and one extreme thermophile, aquifex aeolicus. all three proteins bi ... | 2005 | 15533834 |
| molecular analysis and identification of virulence gene on pr(st98) from multi-drug resistant salmonella typhi. | pr(st98) is a large and conjugative resistant plasmid (r plasmid) of 98.6 mega-dalton from multi-drug resistant salmonella typhi (s. typhi), which was classified to incompatibility group c (inc c). it has been found that prst98 made its host bacteria not only antibiotic resistant but also more virulent. in this study we explored the possibility of plasmid prst98 in s. typhi carrying the salmonella plasmid virulence gene - spv. the plasmid prst98 was isolated, purified and then digested by nine r ... | 2005 | 16191420 |
| isolation of plasmid pkm101 in the stocker laboratory. | pkm101 is a mutagenesis-enhancing resistance transfer plasmid (r plasmid) that was introduced into several tester strains used in the salmonella/microsome mutation assay (ames test). plasmid pkm101 has contributed substantially to the effectiveness of the ames assay, which is used on a world-wide basis to detect mutagens and is required by many government regulatory agencies for approval to market new drugs and other chemical agents. widely used since 1975, the ames test is still regarded as one ... | 2006 | 16716644 |
| quick identification of type i restriction enzyme isoschizomers using newly developed ptypei and reference plasmids. | although dna-recognition sequences are among the most important characteristics of restriction enzymes and their corresponding methylases, determination of the recognition sequence of a type-i restriction enzyme is a complicated procedure. to facilitate this process we have previously developed plasmid r-m tests and the computer program rm search. to specifically identify type-i isoschizomers, we engineered a puc19 derivative plasmid, ptypei, which contains all of the 27 type-i recognition seque ... | 2008 | 18562466 |