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PubMed2006

DNA sequence of a ColV plasmid and prevalence of selected plasmid-encoded virulence genes among avian Escherichia coli strains.

ColV plasmids have long been associated with the virulence of Escherichia coli, despite the fact that their namesake trait, ColV production, does not appear to contribute to virulence. Such plasmids or their associated sequences appear to be quite common among avian pathogenic E. coli (APEC) and are strongly linked to the virulence of these organisms. In the present study, a 180-kb ColV plasmid was sequenced and analyzed. This plasmid, pAPEC-O2-ColV, possesses a 93-kb region containing several putative virulence traits, including iss, tsh, and four putative iron acquisition and transport systems. The iron acquisition and transport systems include those encoding aerobactin and salmochelin, the sit ABC iron transport system, and a putative iron transport system novel to APEC, eit. In order to determine the prevalence of the virulence-associated genes within this region among avian E. coli strains, 595 APEC and 199 avian commensal E. coli isolates were examined for genes of this region using PCR. Results indicate that genes contained within a portion of this putative virulence region are highly conserved among APEC and that the genes of this region occur significantly more often in APEC than in avian commensal E. coli. The region of pAPEC-O2-ColV containing genes that are highly prevalent among APEC appears to be a distinguishing trait of APEC strains.

Animals↗
PubMed2006

Bacillus anthracis virulent plasmid pX02 genes found in large plasmids of two other Bacillus species.

In order to cause the disease anthrax, Bacillus anthracis requires two plasmids, pX01 and pX02, which carry toxin and capsule genes, respectively, that are used as genetic targets in the laboratory detection of the bacterium. Clinical, forensic, and environmental samples that test positive by PCR protocols established by the Centers for Disease Control and Prevention for B. anthracis are considered to be potentially B. anthracis until confirmed by culture and a secondary battery of tests. We report the presence of 10 genes (acpA, capA, capB, capC, capR, capD, IS1627, ORF 48, ORF 61, and repA) and the sequence for the capsule promoter normally found on pX02 in Bacillus circulans and a Bacillus species closely related to Bacillus luciferensis. Tests revealed these sequences to be present on a large plasmid in each isolate. The 11 sequences consistently matched to B. anthracis plasmid pX02, GenBank accession numbers AF188935.1, AE011191.1, and AE017335.3. The percent nucleotide identities for capD and the capsule promoter were 99.9% and 99.7%, respectively, and for the remaining nine genes, the nucleotide identity was 100% for both isolates. The presence of these genes, which are usually associated with the pX02 plasmid, in two soil Bacillus species unrelated to B. anthracis alerts us to the necessity of identifying additional sequences that will signal the presence of B. anthracis in clinical, forensic, and environmental samples.

Bacillus↗
PubMed1998

The 2 micrometer plasmid stability system: analyses of the interactions among plasmid- and host-encoded components.

The stable inheritance of the 2 micrometer plasmid in a growing population of Saccharomyces cerevisiae is dependent on two plasmid-encoded proteins (Rep1p and Rep2p), together with the cis-acting locus REP3 (STB). In this study we demonstrate that short carboxy-terminal deletions of Rep1p and Rep2p severely diminish their normal capacity to localize to the yeast nucleus. The nuclear targeting, as well as their functional role in plasmid partitioning, can be restored by the addition of a nuclear localization sequence to the amino or the carboxy terminus of the shortened Rep proteins. Analyses of deletion derivatives of the Rep proteins by using the in vivo dihybrid genetic test in yeast, as well as by glutathione S-transferase fusion trapping assays in vitro demonstrate that the amino-terminal portion of Rep1p (ca. 150 amino acids long) is responsible for its interactions with Rep2p. In a monohybrid in vivo assay, we have identified Rep1p, Rep2p, and a host-encoded protein, Shf1p, as being capable of interacting with the STB locus. The Shf1 protein expressed in Escherichia coli can bind with high specificity to the STB sequence in vitro. In a yeast strain deleted for the SHF1 locus, a 2 micrometer circle-derived plasmid shows relatively poor stability.

Activating Transcription Factors↗
PubMed2000

RAD51 is required for the repair of plasmid double-stranded DNA gaps from either plasmid or chromosomal templates.

DNA double-strand breaks may be induced by endonucleases, ionizing radiation, chemical agents, and mechanical forces or by replication of single-stranded nicked chromosomes. Repair of double-strand breaks can occur by homologous recombination or by nonhomologous end joining. A system was developed to measure the efficiency of plasmid gap repair by homologous recombination using either chromosomal or plasmid templates. Gap repair was biased toward gene conversion events unassociated with crossing over using either donor sequence. The dependence of recombinational gap repair on genes belonging to the RAD52 epistasis group was tested in this system. RAD51, RAD52, RAD57, and RAD59 were required for efficient gap repair using either chromosomal or plasmid donors. No homologous recombination products were recovered from rad52 mutants, whereas a low level of repair occurred in the absence of RAD51, RAD57, or RAD59. These results suggest a minor pathway of strand invasion that is dependent on RAD52 but not on RAD51. The residual repair events in rad51 mutants were more frequently associated with crossing over than was observed in the wild-type strain, suggesting that the mechanisms for RAD51-dependent and RAD51-independent events are different. Plasmid gap repair was reduced synergistically in rad51 rad59 double mutants, indicating an important role for RAD59 in RAD51-independent repair.

Amino Acid Sequence↗
PubMed2006

Competition between plasmid-bearing and plasmid-free organisms in the host: population dynamics and antibiotic resistance.

OBJECTIVE: To clarify the effects of antibiotic exposure on bacterial antibiotic resistance. MATERIALS AND METHODS: A competitive population dynamics model for plasmid-bearing organisms and plasmid-free organisms in the host was established. The Poincaré-Bendixson theorem was used for analysis. RESULTS: All possible results of the competition dependent on biologically meaningful parameters were obtained, which can be classified into eight categories. With the outcomes of the plasmid model, we discussed the sterilizing effect if an antibiotic was added to the host. CONCLUSION: When antibiotic-resistant bacteria existed in a host, a higher dosage of antibiotics was needed with an increased risk of survival of plasmid-bearing organisms and greater danger of resistance to antibiotics.

Anti-Bacterial Agents↗
PubMed1975

Apparent antagonism by a resident R plasmid for entry of related gentamicin-tobramycin resistance plasmids in Pseudomonas aeruginosa.

From altogether 17 strains of Pseudomonas aeruginosa resistant to gentamicin, isolated in January 1975, 4 have been found to transfer their resistance to gentamicin and tobramycin, along with the resistance to other aminoglycosides, to rifampicin-resistant recipient strains of the same species. In some instances the transfer was strain-specific and therefore it was advisable to use more divergent recipient strains. It was found that a variant of a recipient strain (ML-4258) which already carries an R plasmid (found in the same area in 1972), accepted the Gm-R To-R plasmids with much lower frequencies than the original plasmid-free recipient. From this it may be concluded that R plasmids in P. aeruginosa from the Frankfurt area did not undergo significant genetic alterations within 3 years and thus they might be regarded as phylogenetically related.

Anti-Bacterial Agents↗
PubMed2000

Pitfall of an internal control plasmid: response of Renilla luciferase (pRL-TK) plasmid to dihydrotestosterone and dexamethasone.

The thymidine kinase promoter-Renilla luciferase reporter plasmid (pRL-TK) is commonly used as a control for transfection efficiency in the Dual-Luciferase Reporter Assay System. While investigating hormone response elements in the promoters of the androgen-dependent, epididymis-specific EP2 gene, we found that hormone treatment affected the luciferase activity of pRL-TK-transfected cells. In African Green Monkey Kidney (CV-1) cells, cotransfected transiently with a hormone-responsive promoter-firefly luciferase reporter plasmid and with pRL-TK, Renilla luciferase activity increased in response to dihydrotestosterone (DHT) and decreased in response to dexamethasone (DEX). When a thromboxane synthase promoter Renilla luciferase plasmid (pRL-TS) was used in place of pRL-TK, Renilla luciferase activity remained constant in CV-1 cells treated with DHT but decreased in CV-1 cells treated with DEX. In transfection studies, internal control plasmid expression in response to treatment must be carefully monitored to ensure proper interpretation of normalized results.

Animals↗
PubMed1982

Function of plasmids in the production of aureothricin. I. Elimination of plasmids and alteration of phenotypes caused by protoplast regeneration in Streptomyces kasugaensis.

The spontaneous mutant 18a derived from Streptomyces kasugaensis MB273 exhibited pleiotropic effect such as loss of aerial mycelium formation, aureothricin (AT) production, and of citrullin biosynthesis, as well as changes in plasmid; the mutant required cystine for production of aureothricin. An improved method of protoplast regeneration was applied to S. kasugaensis MB 273-18a and a regeneration efficiency of 90% or more was obtained. Sixty to ninety percent of the colonies regenerated from the 18a protoplasts exhibited reversion of the pleiotropic mutation in 18a. Moreover, of 13 regenerated strains which showed these drastic phenotypic variations, it was found that their plasmid types varied. These types could be divided into two groups; the RI type (5 strains) which contained a large amount of pSK2, a small amount of pSK3 and no pSK1, and the RII type (8 strains) in which no closed-circular DNA was detected. From these results, the following conclusions were obtained. First, plasmid curing in RII type strains and also the variation of plasmid copy in the RI type strains occurred as the result of protoplast regeneration. Second, the structural genes for biosynthesis of AT probably exist on chromosome. Third, regeneration of 18a protoplasts causes the reversion of pleiotropic mutation with high frequency. A working hypothesis was proposed to explain these complex phenomena.

Anti-Bacterial Agents↗
PubMed2002

[Phage types and plasmid profiles of plasmid DNA strains of Salmonella enterica subsp. enterica ser. Enteritidis (S. Enteritidis) isolated from food poisoning outbreaks in 2001].

Salmonella Enteritidis strains are the most often isolated Salmonella serovar in Poland. In the present study, phage typing, antibiotic resistance testing and plasmid profile analysis, have been applied to characterise 41 Polish S. Enteritidis isolates originated from human cases of salmonellosis and from other sources. The typing phages of Ward and colleagues scheme were used to type a total of 41 S. Enteritidis strains coming from Poland. All 41 strains were typable and 5 different phage types were observed. Among 41 strains tested, both PT6 and PT21 were recognized in the 15 strains (36.6%). Nine strains (22%) belonged to phage type 8. The others PTs were represented by small amount of strains (PT1var and PT4). Among all tested isolates only 4 different plasmid profiles were observed. Of the 41 strains investigated, 16 (39%) contained the 57 kb plasmid alone. The remaining 25 strains (61%) except 57 kb plasmid, possessed additional DNA particles. The probable phage type conversion of PT21 to PT1var strain, possibly connected with smaller DNA particle presence, was observed. This hypothesis needs confirmation. The real S. Enteritidis epidemiological situation in Poland should be known after introducing of systematic, annual research program.

Bacteriophage Typing↗
PubMed1991

Characterization of the natural deletion mutant of plasmid pXZ10145 in Corynebacterium glutamicum and construction of a recombinant plasmid.

Plasmid pNAT65, carrying the chloramphenicol resistance marker, was chosen from a number of natural deletion mutants of pXZ10145 when pXZ10145 DNA, originally isolated from Corynebacterium glutamicum 1014-6T, was used to transform the protoplast of Corynebacterium crenatum T6-13. The size of pNAT65 was 2.4 kb, determined by electrophoresis on 0.7% agarose gel. The physical map of plasmid pNAT65 was determined. One recombinant plasmid, pNAR67, was constructed with the DNA fragments of pNAT65 and pBR322 digested respectively with EcoRI. This plasmid was capable of replication in E. coli, expressing ampicillin and tetracycline resistance; but with lower chloramphenicol, the resistance was only about 2 micrograms/ml.

Chromosome Deletion↗
PubMed1990

[Isolation of transmissible cointegrates of Yersinia pestis plasmids pYV and pYT with the plasmid RP4::Mu cts 62, IncP1].

The transmissible cointegrates of the Yersinia pestis plasmids pYV and pYT with the broad host range plasmid RP4::Mu cts62 of the incompatibility group IncP have been constructed by the in vivo recombination. The cointegrative plasmid pKR14 (pYV76 omega RP4::Mu cts62) conferred on the transconjugants the properties of Ca2(+)-dependence at 37 degrees C, V-antigen synthesis, RP4 plasmid markers (ApR, KmR, TcR), immunity to the lysis by the bacteriophage Mu cts62 and incompatibility with the homologous replicon pYV76. Cointegrates pKR103 and pKR106 (pYT omega RP4::Mu cts62) conferred on the transconjugant clones the ability to synthesize the "mouse" toxin and fraction I. The capability of Escherichia coli cells to synthesize the latter products has been demonstrated together with the deficiency of these cells to transport the synthesized fraction I to the cell surface.

Antigens, Bacterial↗
PubMed1989

[Intra- and intermolecular recombination of test plasmids in K12 Escherichia coli cells carrying an RTF derivative of the R1drd-19 plasmid].

The RTF derivative of the plasmid R1drd-19 was found to stimulate recombination of the tester plasmids in a recB mutant of Escherichia coli K12. The frequency of intramolecular recombination is increased 3.5 and 20-fold, as compared to the one in rec+ and rec- strains, respectively. The frequency of interplasmid recombination is enhanced 4 and 9-fold, respectively. Considerable heterogeneity of the recombination products of the tester plasmid intramolecular recombination in recB-/RTFR1-19 strain has been revealed. It is hypothesized that a "recombinase" encoded by Rldrd-19 plasmid determines a new minor pathway in recB- (Rec P) which differs in activity and, perhaps substrate specificity from the main Rec BCD pathway.

Escherichia coli↗
PubMed1987

[Detailed mapping of the Hly-region of the plasmid pHly241. Homology of the hemolysis determinants of plasmids pHly241 and pHly195].

Data on the hemolysin synthesis determined by the plasmid pHly241, belonging to the incompatibility group I2, and its derivatives are presented in this paper. The restriction analysis of the pHly241 plasmid has resulted in the detailed mapping of the hly determinant region in the plasmid. The substantial homology has been demonstrated between the regions of the plasmids pHly241 and pHly195 coding for hemolysin synthesis and excretion from the bacterial cell.

Base Sequence↗
PubMed1978

[Transforming activity of plasmid R6K DNA on Serratia marcescens strain 20-10. The behavior of the plasmid in the transformants].

The authors described transformation of S. marcescens, strain 20-10, of the isolated R6K plasmide DNA. As demonstrated by centrifugation in cesium chloride gradient and electrophoresis in agarose, the plasmide was present in the transformants in the form identical to R6K in E. coli K12. Analysis of the transforming activity of R6K plasmide from Serratia and E. coli K12 strains with a complete and defective restriction system showed S. marsescens, strain 20-10, to possess specific system of restriction and modification. In studying beta-lactamase activity and Serratia and E. coli strains ampicillin and streptomycin resistance revealed differences in the phenotypical expression of the plasmide signs in the heterologous and homologous host.

DNA, Bacterial↗
PubMed1978

[Antibiotic formation in plasmid and plasmid-free strains].

Antibiotic activity of three plasmid and three plasmid-free strains of Bacillus pumilus was studied. The antibiotic activity was found in one plasmid and two plasmid-free strains. It was supposed that both the chromosomic and extrachromosomic genes could participate in regulation of the antibiotic production in Bac. pumilus. It was shown that the antibiotics produced by Bac. pumilus had a very narrow spectrum and inhibited multiplication only of several grampositive bacteria.

Anti-Bacterial Agents↗
PubMed1979

[Effect of plasmid F'Col+trp+ on the transfer of plasmid RP4].

Interaction of conjugative plasmids F'colV colB trp and PR4 in Escherichia coli host was studied during the transfer of the plasmids from cell to cell. The plasmid F'colV colB trp is found to stimulate the transfer of RP4 from the diplasmid strain. This seems to be due to stabilization of the conjugating pairs which require normal pili coded by the plasmid F'colV colB trp.

Coliphages↗