Characteristics of transduction in Erwinia by phage 59

A temperate bacteriophage 59 from polylysogenic strain Erwinia carotovora 268 transduces the following genetic markers: arg+, ilv+, leu+, met+, thr+, thy+, trp+, ura+. The transduction frequencies varied from 1 x 10(-8)- to 1 x 10(-6) and dependent on the multiplicity of infection, UV-irradiation of transducing bacteriophage, the nature of phage lysates. The characteristics of single transductants have been studied.Analysis of the obtained results suggests bacteriophage 59 to perform the generalized transduction.     

pULB113, an RP4::mini-Mu plasmid, mediates chromosomal mobilization and R-prime formation in Erwinia amylovora, Erwinia chrysanthemi, and subspecies of Erwinia carotovora.

The RP4::mini-Mu plasmid pULB113, transferred from Escherichia coli strain MXR, was stable and transfer proficient in Erwinia amylovora strain EA303, E. carotovora subsp. atroseptica strain ECA12, E. carotovora subsp. carotovora strain ECC193, and E. chrysanthemi strain EC183. The plasmid mobilized an array of Erwinia sp. chromosomal markers (E. amylovora: his+,ilv+,rbs+,ser+,thr+;E. chrysanthemi:arg+,his+,ilv+,leu+; E. carotovora subsp. atroseptica: arg+,gua+,leu+,lys+,pur+,trp+; E. carotovora subsp. carotovora: arg+,gua+,leu+,lys+,out+[export of enzymes],pur+,trp+), suggesting random interactions of the plasmid with the chromosomes. In E. carotovora subsp. carotovora, pULB113-mediated two-factor crosses revealed linkage between three auxotrophic markers and the out loci. The export of pectate lyase, polygalacturonase, and cellulase and the maceration of potato tuber tissue occurred with Out+, but not Out-, strains of E. carotovora subsp. carotovora, indicating the importance of enzyme export in plant tissue maceration. Erwinia sp. donors harboring pULB113 complemented mutations in various biosynthetic and catabolic genes (arg, gal, his, leu, met, pro, pur, thy) in Escherichia coli recA strains. Escherichia coli transconjugants harbored pULB113 primes as indicated by the cotransfer of Erwinia genes and pULB113 markers and a change in plasmid mass. Moreover, the PstI and SmaI cleavage patterns of selected pULB113 primes were different from those of pULB113. pULB113 primes carried DNA insertions ranging from 3 to about 160 kilobases. These findings indicate that pULB113 is useful for in vivo gene cloning and genetic analysis of various enterobacterial phytopathogens.     

pULB113, an RP4::mini-Mu plasmid, mediates chromosomal mobilization and R-prime formation in Erwinia amylovora, Erwinia chrysanthemi, and subspecies of Erwinia carotovora

The RP4::mini-Mu plasmid pULB113, transferred from Escherichia coli strain MXR, was stable and transfer proficient in Erwinia amylovora strain EA303, E. carotovora subsp. atroseptica strain ECA12, E. carotovora subsp. carotovora strain ECC193, and E. chrysanthemi strain EC183. The plasmid mobilized an array of Erwinia sp. chromosomal markers (E. amylovora: his+,ilv+,rbs+,ser+,thr+;E. chrysanthemi:arg+,his+,ilv+,leu+; E. carotovora subsp. atroseptica: arg+,gua+,leu+,lys+,pur+,trp+; E. carotovora subsp. carotovora: arg+,gua+,leu+,lys+,out+[export of enzymes],pur+,trp+), suggesting random interactions of the plasmid with the chromosomes. In E. carotovora subsp. carotovora, pULB113-mediated two-factor crosses revealed linkage between three auxotrophic markers and the out loci. The export of pectate lyase, polygalacturonase, and cellulase and the maceration of potato tuber tissue occurred with Out+, but not Out-, strains of E. carotovora subsp. carotovora, indicating the importance of enzyme export in plant tissue maceration. Erwinia sp. donors harboring pULB113 complemented mutations in various biosynthetic and catabolic genes (arg, gal, his, leu, met, pro, pur, thy) in Escherichia coli recA strains. Escherichia coli transconjugants harbored pULB113 primes as indicated by the cotransfer of Erwinia genes and pULB113 markers and a change in plasmid mass. Moreover, the PstI and SmaI cleavage patterns of selected pULB113 primes were different from those of pULB113. pULB113 primes carried DNA insertions ranging from 3 to about 160 kilobases. These findings indicate that pULB113 is useful for in vivo gene cloning and genetic analysis of various enterobacterial phytopathogens.     

Isolation and characterization of Hfr strains of Erwinia amylovora

Hfr strains (Hfr 159 and its derivatives, Hfr 160 and Hfr 161) were constructed from Erwinia amylovora ICPB EA178 by introducing an Escherichia coli F'his+ plasmid and then selecting for integration of F'his+ after treatment with acridine orange. The Hfr strains were relatively stable upon repeated transfers on nonselective media. Interrupted mating experiments and analyses of inheritance of unselected markers showed that his+ is transferred by Hfr 159 as the proximal marker at a relatively high frequency (about 5 x 10(-4) recombinants per input donor cell), followed by ilv+, orn+, arg+, pro+, rbs+, met+, trp+, leu+, ser+, and thr+ (not necessarily in that precise order). The donor strains, previously constructed in E. amylovora by integration of F'lac+ from E. coli transfer cys+ as the proximal marker followed by ser+. Further analysis of one of those earlier donor strains, Hfr99, showed that ser+ is followed by arg+, orn+, met+, pro+, leu+, ilv+, rbs+, his+, trp+, and thr+ (not necessarily in that precise order). Thus, the Hfr strains constructed by integration of F'his+ are different, in terms of origin and direction of transfer, from those derived from integration of F'lac+. The applicability of these Hfr strains to mapping the genes on the E. amylovora chromosome is indicated.     

Transduction of Escherichia coli by bacteriophage P1 in soil.

Transduction of Escherichia coli W3110(R702) and J53(RP4) (10(4) to 10(5) CFU/g of soil) by lysates of temperature-sensitive specialized transducing derivatives of bacteriophage P1 (10(4) to 10(5) PFU/g of soil) (P1 Cm cts, containing the resistance gene for chloramphenicol, or P1 Cm cts::Tn501, containing the resistance genes for chloramphenicol and mercury [Hg]) occurred in soil amended with montmorillonite or kaolinite and adjusted to a -33-kPa water tension. In nonsterile soil, survival of introduced E. coli and the numbers of E. coli transductants resistant to chloramphenicol or Hg were independent of the clay amendment. The numbers of added E. coli increased more when bacteria were added in Luria broth amended with Ca and Mg (LCB) than when they were added in saline, and E. coli transductants were approximately 1 order of magnitude higher in LCB; however, the same proportion of E. coli was transduced with both types of inoculum. In sterile soil, total and transduced E. coli and P1 increased by 3 to 4 logs, which was followed by a plateau when they were inoculated in LCB and a gradual decrease when they were inoculated in saline. Transduction appeared to occur primarily in the first few days after addition of P1 to soil. The transfer of Hg or chloramphenicol resistance from lysogenic to nonlysogenic E. coli by phage P1 occurred in both sterile and nonsterile soils. On the basis of heat-induced lysis and phenotype, as well as hybridization with a DNA probe in some studies, the transductants appeared to be the E. coli that was added. Transduction of indigenous soil bacteria was not unequivocally demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transduction of Escherichia coli by bacteriophage P1 in soil

Transduction of Escherichia coli W3110(R702) and J53(RP4) (10(4) to 10(5) CFU/g of soil) by lysates of temperature-sensitive specialized transducing derivatives of bacteriophage P1 (10(4) to 10(5) PFU/g of soil) (P1 Cm cts, containing the resistance gene for chloramphenicol, or P1 Cm cts::Tn501, containing the resistance genes for chloramphenicol and mercury [Hg]) occurred in soil amended with montmorillonite or kaolinite and adjusted to a -33-kPa water tension. In nonsterile soil, survival of introduced E. coli and the numbers of E. coli transductants resistant to chloramphenicol or Hg were independent of the clay amendment. The numbers of added E. coli increased more when bacteria were added in Luria broth amended with Ca and Mg (LCB) than when they were added in saline, and E. coli transductants were approximately 1 order of magnitude higher in LCB; however, the same proportion of E. coli was transduced with both types of inoculum. In sterile soil, total and transduced E. coli and P1 increased by 3 to 4 logs, which was followed by a plateau when they were inoculated in LCB and a gradual decrease when they were inoculated in saline. Transduction appeared to occur primarily in the first few days after addition of P1 to soil. The transfer of Hg or chloramphenicol resistance from lysogenic to nonlysogenic E. coli by phage P1 occurred in both sterile and nonsterile soils. On the basis of heat-induced lysis and phenotype, as well as hybridization with a DNA probe in some studies, the transductants appeared to be the E. coli that was added. Transduction of indigenous soil bacteria was not unequivocally demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Construction of a broad host range cosmid cloning vector and its use in the genetic analysis of Rhizobium mutants

We have constructed a cosmid derivative of the low copy-number broad host-range cloning vector pRK290 (Ditta et al., 1980) by inserting a 1.6-kb Bg/II fragment containing lambda cos into the unique Bg/II site in pRK290. The new vector, pLAFR1, is 21.6 kb long, confers tetracycline resistance, contains a unique EcoRI site, and can be mobilized into and stably replicates within many Gram-negative hosts. We constructed a clone bank of Rhizobium meliloti DNA in pLAFR1 using a partial EcoRI digest. The mean insert size was 23.1 kb. When the clone bank was mated (en masse) from Escherichia coli to various R. meliloti auxotrophic mutants, tetracycline-resistant (Tcr) transconjugants were obtained at frequencies ranging from 0.1 to 0.8, and among these, prototrophic colonies were obtained at frequencies ranging from 0.001 to 0.007. pLAFR1 cosmids were mobilized from R. meliloti prototrophic colonies into E. coli and then reintroduced into R. meliloti auxotrophs. In most cases, 100% of these latter Tcr transconjugants were prototrophic.     

Efficient introduction of cloned mutant alleles into the Escherichia coli chromosome.

An efficient method for moving mutations in cloned Escherichia coli DNA from plasmid vectors to the bacterial chromosome was developed. Cells carrying plasmids that had been mutated by the insertion of a resistance gene were infected with lambda phage containing homologous cloned DNA, and resulting lysates were used for transduction. Chromosomal transductants (recombinants) were distinguished from plasmid transductants by their ampicillin-sensitive phenotype, or plasmid transductants were avoided by using a recBC sbcB E. coli strain as recipient. Chromosomal transductants were usually haploid when obtained in a nonlysogen because of selection against the lambda vector and partially diploid when obtained in a lysogen. Pure stocks of phage that carry the resistance marker and transduce it at high frequency were obtained from transductant bacteria. The lambda-based method for moving mutant alleles into the bacterial chromosome described here should be useful for diverse analyses of gene function and genome structure.     

Isolation and Characterization of a New Generalized Transducing Bacteriophage Different from Pl in Escherichia coli

A new generalized transducing bacteriophage in the Escherichia coli system was isolated and characterized. This phage, designated D108, makes clear plaques on E. coli K-10, K-12, K-12(P1kc), K-12(D6), B/r, C, and 15 T(-), and Shigella dysenteriae. The plaque of phage D108 is larger in size than that of phage P1kc. Electron-microscopic observation revealed that phages D108 and P1kc are morphologically different from each other, suggesting that phage D108 belongs to a phage group different from phage P1. The fact that all of the 10 markers tested were transduced by phage D108 indicates that this phage is a generalized transducing phage in the E. coli system. The transduction frequency by phage D108 of chromosomal markers and of a drug resistance factor (R factor) ranged from 2 x 10(-6) to 3 x 10(-8) and 3 x 10(-9) to 6 x 10(-10) per phage, respectively. The cotransduction frequency of the thr and leu markers was 2.8% for phage P1kc and 1.5% for phage D108. The CM and TC markers (chloramphenicol-resistant and tetracycline-resistant markers, respectively) of the R factor were not cotransduced by phage D108, but the markers were generally cotransduced by phage P1kc. The results suggest that the transducing particle of phage D108 contains a smaller amount of host deoxyribonucleic acid than does phage P1kc.     

Plaque assay for lambda transducing phage carrying the E. coli metB gene

A halo plaque assay has been developed for the detection of nondefective lambda transducing phage carrying functional alleles of the metB gene of Escherichia coli K12. The assay is based upon the production of phage plaques on lawns of metB- bacterial cells which are supplemented with limiting amounts of methionine and upon the subsequent transduction of methionine-starved cells in the lawn surrounding the plaques. The resulting prototrophic transductants give rise to a halo of bacterial growth surrounding the plaque. A precise genotype can be ascribed to the characteristic morphologies of selected haloes. This technique has general application for all biosynthetic markers.     

F'-plasmid transfer from Escherichia coli to Pseudomonas fluorescens.

Various F' plasmids of Escherichia coli K-12 could be transferred into mutants of the soil strain 6.2, classified herein as a Pseudomonas fluorescens biotype IV. This strain was previously found to receive Flac plasmid (N. Datta and R.W. Hedges, J. Gen Microbiol. 70:453-460, 1972). ilv, leu, met, arg, and his auxotrophs were complemented by plasmids carrying isofunctional genes; trp mutants were not complemented or were very poorly complemented. The frequency of transfer was 10(-5). Subsequent transfer into other P. fluorescens recipients was of the same order of magnitude. Some transconjugants were unable to act as donors, and these did not lose the received information if subcultured on nonselective media. Use of F' plasmids helped to discriminate metabolic blocks in P. fluorescens. In particular, metA, metB, and argH mutants were so distinguished. In addition, F131 plasmid carrying the his operon and a supD mutation could partially relieve the auxotrophy of thr, ilv, and metA13 mutants, suggesting functional expression of E. coli tRNA in P. fluorescens. In P. fluorescens metA Rifr mutants carrying the F110 plasmid, which carried the E. coli metA gene and the E. coli rifs allele, sensitivity to rifampin was found to be dominant at least temporarily over resistance. This suggests interaction of E. coli and P. fluorescens subunits of RNA polymerase. his mutations were also complemented by composite P plasmids containing the his-nif region of Klebsiella pneumoniae (plasmids FN68 and RP41). nif expression could be detected by acetylene reduction in some his+ transconjugants. The frequency of transfer of these P plasmids was 5 X 10(-4).     

Transduction, Restriction and Recombination Patterns in Escherichia Coli

Chromosomal DNA from several Escherichia coli reference (ECOR) strains was transduced by bacteriophage P1 into E. coli strain K12 W3110 trpA33. Recombination patterns of the transductants were determined by restriction fragment length polymorphism over a 40-kb region centering on a single marker (trpA(+)) in the tryptophan operon. These experiments demonstrate that transduction between different strains of E. coli can result in recombinational replacements that are small in comparison to the entrant molecule (replacements average 8-14 kb, whereas P1 packages ~ 100 kb) often in a series of discrete segments. The transduction patterns generated resemble the natureal mosaic sequence patterns of the ECOR strains described in previous work. Extensive polymorphisms in the restriction-modification systems of the ECOR strains are a possible explanation for the sequence patterns in nature. To test this possibility, two transductants were back-transduced into strain K12 W3110 trpA33. The resulting patterns were strikingly different from the original transductions. The size of the replacements was greater, and no multiple replacements were observed, suggesting a role for restriction-modification systems in the transduction patterns and perhaps for the mosaic sequence patterns in nature.     

Genetic analysis of chromosomal resistance to trimethoprim derived from clinical isolates of Escherichia coli

Chromosomal genes conferring resistance to trimethoprim were transferred from three independently isolated thy+ clinical strains of Escherichia coli to Escherichia coli K12 by using P1 transduction. Trimethoprim-resistant transductants were obtained less frequently than transductants of other chromosomal markers, suggesting that there were problems related to the expression of the trimethoprim resistance genes in E. coli K12. Mapping studies revealed that one of the resistance determinants was located at a similar position on the chromosome (1 min) to the fol-type mutations previously described in E. coli K12. The two remaining resistance determinants mapped at separate positions between 2.5 and 3 min on the chromosome. The presence of one of these determinants reduced the efficiency with which either donor or recipient cells carrying it could participate in conjugation mediated by the sex factor F and also resulted in phenotypic interaction with the azi gene. The mechanisms of trimethoprim resistance in the three clinical E. coli isolates studied were more complex and diverse than was expected from previous studies of E. coli K12 mutants.     

Transposition of the phage D3112 genome in Escherichia coli cells

It has been demonstrated that the genome of phage D3112 of Preudomonas aeruginosa can be transposed into Escherichia coli chromosome as a component of the hybrid plasmid RP4 TcrKms::D3112. Also, transposition of D3112 from E. coli (D3112) chromosome into RP4 plasmid occurs. The phage stimulates the chromosome mobilizing activity of RP4 plasmid, similar to other transposons. E. coli (RP4::D3112) cells were previously shown to form no colonies at 30 degrees C. Auxotrophic mutants and mutants incapable of utilizing different carbohydrates were found among E. coli clones survived after a long incubation at 30 degrees C (at frequencies approximately 10(-3) - 10(-4). These mutants inherited stably the capability to produce D3112 phage. E. coli auxotrophic mutants have arisen indeed as a consequence of phage integration into the E. coli chromosome, since prototrophic transductants derived from these mutants after their treatment with generalized transducing P1 phage have lost the ability to produce D3112 phage. Clones with mutations in Km or Tc genes of RP4 plasmid, occurring at high frequencies (about 3%) were found after introduction of RP4 into E. coli (D3112). These mutant RP4 plasmids carry insertions of D3112 genomes. Clones of E. coli which lost mutant plasmids still produce D3112 and retain their initial auxotrophic mutations.     

Transposon Tn10-like tetracycline resistance determinants in Haemophilus parainfluenzae.

Tetracycline resistance (Tcr) determinants from three different strains of Haemophilus parainfluenzae expressed 10-fold higher levels of resistance when mated into Escherichia coli. No plasmid was found in any of the E. coli recipients, even in matings in which a plasmid was identified in the donor Haemophilus sp. The Tcr determinant from Haemophilus sp. caused instability of resident plasmids in the recipient E. coli: all plasmids were lost within 30 generations in antibiotic-free media. However, by serial subculture in antibiotics, stable resident plasmids were obtained which carried the Tcr determinant from Haemophilus sp. and were transferable by conjugation and transformation among E. coli strains. All Haemophilus determinants hybridized with a probe for the Tcr determinant on Tn10, which bears inducible Tcr. However, Haemophilus determinants were constitutively resistant to tetracycline in the Haemophilus donors and in the E. coli recipients. This constitutive expression was recessive to wild-type Tn10 in the same cell, indicating that the constitutive phenotype resulted from the absence of an active repressor. Restrictive enzyme analysis of various E. coli plasmid derivatives bearing a Tcr determinant from Haemophilus sp. demonstrated that the inserted DNA was of similar size (8.95 to 9.35 kilobases), close to that of Tn10. Heteroduplex analysis and DNA:DNA hybridization confirmed that the Tcr determinant from Haemophilus sp. had greater than 90% homology with the Tn10 determinant, including the DNA sequence for the repressor.     

Localized hydroxylamine mutagenesis, and cotransduction of threonine and lysine genes, in Streptomyces venezuelae

A lysate of the generalized transducing phage SV1, grown on the prototrophic type strain 10712 of Streptomyces venezuelae, was mutagenized with hydroxylamine and used to transduce a lysineless auxotroph to lysine independence on supplemented minimal agar. A complex threonine mutant, strain VS95, was isolated from among the transductants and was shown to be carrying at least two different thr mutations. These were about 50% cotransducible with alleles of four independently isolated lysA mutations, as were two other independently isolated threonine mutations, thr-1 and hom-5. The location of thr genes close to lysA occurs in at least three other streptomycetes, but apparently not in Streptomyces coelicolor A3(2), in which the lysA and thr loci are at diametrically opposite locations on the linkage map. This first observation of cotransduction between loci governing the biosynthesis of different amino acids in the genus Streptomyces demonstrates the feasibility of fine-structure genetic analysis by transduction in these antibiotic-producing bacteria.     

Functional expression of two Bacillus subtilis chromosomal genes in Escherichia coli.

EcoRI-cleaved deoxyribonucleic acid segments carrying two genes from Bacillus subtilis, pyr and leu, have been cloned in Escherichia coli by insertion into a derivative of the E. coli bacteriophage lambda. Lysogenization of pyrimidine- and leucine-requiring auxotrophs of E. coli by the hybrid phages exhibited prototrophic phenotypes, suggesting the expression of B. subtilis genes in E. coli. Upon induction, these lysogens produced lysates capable of transducing E. coli pyr and leu auxotrophs to prototrophy with high frequency. Isolated DNAs of these bacteriophages have the ability to transform B. subtilis auxotrophs to pyr and leu independence and contain EcoRI-cleaved segments which hybridize to corresponding segments of B. subtilis.     

Cloning and characterization of a Bacteroides conjugal tetracycline-erythromycin resistance element by using a shuttle cosmid vector.

The Bacteroides conjugal tetracycline resistance (Tcr) elements appear not to be plasmids. In many cases, resistance to erythromycin (Emr) is cotransferred with Tcr. Using a newly constructed shuttle cosmid, pNJR1, we cloned 44 to 50 kilobase pairs of a conjugal Tcr Emr element on overlapping cosmid clones. Cosmid libraries were made in Escherichia coli with DNA from the original clinical Bacteroides thetaiotaomicron DOT strain containing Tcr Emr-DOT or from a Bacteroides uniformis Tcr Emr-DOT transconjugant strain. The cosmid clones were mobilized from E. coli into B. uniformis in groups of 10 to 20 per filter mating, with selection for Tcr or Emr transconjugants. The Tcr and Emr genes were cloned both separately and together on 30-kilobase-pair fragments. Several of the Tcr clones also contained transfer genes that permitted self-transfer of the cosmid from B. uniformis donors to E. coli or B. uniformis recipients. Neither the Tcr nor the Emr gene conferred resistance on E. coli, and the transfer-proficient clones did not self-transfer out of E. coli. Southern blot analysis was used to compare DNA from independently isolated Bacteroides strains carrying conjugal Tcr or Tcr Emr elements and their respective B. uniformis transconjugants. Results of these analyses indicate that there are large regions of homology, including regions outside the Tcr and Emr genes, but that the elements are not identical. Some Tcr clones contained a region which hybridized to chromosomal DNA from the wild-type B. uniformis recipient strain that did not carry the Tcr Emr-DOT element. This region of homology appeared not to be a junction fragment. It was not required in a Bacteroides recipient for successful transfer of the Tcr Emr element. Although we are not sure we have cloned a junction fragment between the Tcr Emr-DOT element and the B. uniformis chromosome, the preliminary function and restriction map appears to be linear.     

Characterization of Pyridoxine Auxotrophs of Escherichia coli: P1 Transduction

Pyridoxine mutants of Escherichia coli B, previously divided into a minimum of six groups by cross-feeding tests, were characterized by transduction studies performed with phage P1bt. The results of these studies allowed division of pyridoxine mutants into five unlinked groups and set the minimum number of enzymes between pyridoxal phosphate and a metabolite common to other pathways at six or seven, with the probable maximum at ten. One group was shown to be linked to thr, leu, and pyrA.     

Lambda phagemids and their transducing properties

Two recombinant lambda DNAs, lambda gt::pMB9 and lambda NM::pBR322, containing, respectively, the pMB9 and pBR322 replicon were constructed and characterized. Both constructs (phagemid DNAs) transfect Escherichia coli cells, producing mature infectious phage progenies. Alternatively, drug-resistant colonies of transductants can be selected upon infection with these phages (phagemid particles) that maintain phagemid DNA in the cell in the form of covalently closed circular plasmids. The efficiency of transduction for nonlysogenic E. coli strains with lambda gt::pMB9 phage producing lambda repressor cIts ranges from 10(-7) to 10(-2) transductant colonies per input phage, depending on the temperature and strain used, while lambda NM::pBR322 phage carrying imm21 transduces with a frequency of up to 1. This means that each lambda NM::pBR322 phagemid particle is capable of establishing itself in the cell as a nonlethal plasmid, permitting formation of a resistant bacterial colony. The maximal level of transduction with lambda gt::pMB9 was obtained when E. coli cells lysogenic for lambda were used. Thus, we believe that the efficiency of transduction is determined by the turn-on of the phage repressor in the transductant. In addition, we have found that all lambda gt::pMB9-containing transductants under certain conditions harbor precisely excised pMB9; excision of pBR322 from lambda NM::pBR322 has not been observed.