Transposition of Tn5096 and other IS493 derivatives in Streptomyces griseofuscus

Immunomodulatory Therapies for the Treatment of Graft-versus-host Disease

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is a potentially curative therapy for patients suffering from hematological malignancies, and its therapeutic success is based on the graft-versus-leukemia (GvL) effect. Severe acute and chronic graft-versus-host disease (GvHD) are life-threatening complications after allo-HCT. To date, most of the approved treatment strategies for GvHD rely on broadly immunosuppressive regimens, which limit the beneficial GvL effect by reducing the cytotoxicity of anti-leukemia donor T-cells. Therefore, novel therapeutic strategies that rely on immunomodulatory rather than only immunosuppressive effects could help to improve patient outcomes. Treatments should suppress severe GvHD while preserving anti-leukemia immunity. New treatment strategies include the blockade of T-cell activation via inhibition of dipeptidyl peptidase 4 and cluster of differentiation 28-mediated co-stimulation, reduction of proinflammatory interleukin (IL)-2, IL-6 and tumor necrosis factor-α signaling, as well as kinase inhibition. Janus kinase (JAK)1/2 inhibition acts directly on T-cells, but also renders antigen presenting cells more tolerogenic and blocks dendritic cell-mediated T-cell activation and proliferation. Extracorporeal photopheresis, hypomethylating agent application, and low-dose IL-2 are powerful approaches to render the immune response more tolerogenic by regulatory T-cell induction. The transfer of immunomodulatory and immunosuppressive cell populations, including mesenchymal stromal cells and regulatory T-cells, showed promising results in GvHD treatment. Novel experimental procedures are based on metabolic reprogramming of donor T-cells by reducing glycolysis, which is crucial for cytotoxic T-cell proliferation and activity.

Efficient transposition of Tn4556 by alterations in inverted repeats using a delivery vector carrying a counter-selectable marker for Streptomyces

A 6625-base pair transposon, Tn4556, was initially isolated from a Streptomyces strain and a sequence analysis was performed; however, its annotation data remain incomplete. At least three positions were identified as frameshift and base-exchange errors by resequencing. The revised sequence revealed that Tn4556 contains four open reading frames that encode transposase, methyltransferase, isoprenyl diphosphate transferase, and resolvase, respectively. Thirty-eight-base pair inverted repeat (IR) sequences at both ends contained a 1-bp mismatch flanked by a target duplication site, and transposition efficiency was improved by the replacement of imperfectly matched IR-L to perfectly matched IR-L. The detection of Tn4556 transposition was markedly facilitated using a delivery vector carrying a strictly counter-selectable marker for Streptomyces strains.

Genetic manipulation of secondary metabolite biosynthesis for improved production in Streptomyces and other actinomycetes

Actinomycetes continue to be important sources for the discovery of secondary metabolites for applications in human medicine, animal health, and crop protection. With the maturation of actinomycete genome mining as a robust approach to identify new and novel cryptic secondary metabolite gene clusters, it is critical to continue developing methods to activate and enhance secondary metabolite biosynthesis for discovery, development, and large-scale manufacturing. This review covers recent reports on promising new approaches and further validations or technical improvements of existing approaches to strain improvement applicable to a wide range of Streptomyces species and other actinomycetes.

Microbial gutta-percha degradation shares common steps with rubber degradation by Nocardia nova SH22a

Nocardia nova SH22a, a bacterium capable of degrading gutta-percha (GP) and natural rubber (NR), was used to investigate the GP degradation mechanism and the relations between the GP and NR degradation pathways. For this strain, a protocol of electroporation was systematically optimized, and an efficiency of up to 4.3 × 10(7) CFU per μg of plasmid DNA was achieved. By applying this optimized protocol to N. nova SH22a, a Tn5096-based transposon mutagenesis library of this bacterium was constructed. Among about 12,000 apramycin-resistant transformants, we identified 76 stable mutants defective in GP or NR utilization. Whereas 10 mutants were specifically defective in GP utilization, the growth of the other 66 mutants was affected on both GP and NR. This indicated that the two degradation pathways are quite similar and share many common steps. The larger number of GP-degrading defective mutants could be explained in one of two ways: either (i) the GP pathway is more complex and harbors more specific steps or (ii) the steps for both pathways are almost identical, but in the case of GP degradation there are fewer enzymes involved in each step. The analysis of transposition loci and genetic studies on interesting genes confirmed the crucial role of an α-methylacyl-coenzyme A racemase in the degradation of both GP and NR. We also demonstrated the probable involvement of enzymes participating in oxidoreduction reactions, β-oxidation, and the synthesis of complex cell envelope lipids in the degradation of GP.

In vivo Tn5-based transposon mutagenesis of Streptomycetes

This paper reports the in vivo expression of the synthetic transposase gene tnp(a) from a hyperactive Tn5 tnp gene mutant in Streptomyces coelicolor. Using the synthetic tnp(a) gene adapted for Streptomyces codon usage, we showed random insertion of the transposon into the Streptomycetes genome. The insertion frequency for the hyperactive Tn5 derivative is 98% of transformed S. coelicolor cells. The random transposition has been confirmed by the recovery of ~1.1% of auxotrophs. The Tn5 insertions are stably inherited in the absence of apramycin selection. The transposon contains an apramycin resistance selection marker and an R6Kgamma origin of replication for transposon rescue. We identified the transposon insertion loci by random sequencing of 14 rescue plasmids. The majority of insertions (12 of 14) were mapped to putative open-reading frames on the S. coelicolor chromosome. These included two new regulatory genes affecting S. coelicolor growth and actinorhodin biosynthesis.

Establishment of Tn5096-based transposon mutagenesis in Gordonia polyisoprenivorans

The transposons Tn5, Tn10, Tn611, and Tn5096 were characterized regarding transposition in Gordonia polyisoprenivorans strain VH2. No insertional mutants were obtained employing Tn5 or Tn10. The thermosensitive plasmid pCG79 harboring Tn611 integrated into the chromosome of G. polyisoprenivorans; however, the insertional mutants were fairly unstable und reverted frequently to the wild-type phenotype. In contrast, various stable mutants were obtained employing Tn5096-mediated transposon mutagenesis. Auxotrophic mutants, mutants defective or deregulated in carotenoid biosynthesis, and mutants defective in utilization of rubber and/or highly branched isoprenoid hydrocarbons were obtained by integration of plasmid pMA5096 harboring Tn5096 as a whole into the genome. From about 25,000 isolated mutants, the insertion loci of pMA5096 were subsequently mapped in 20 independent mutants in genes which could be related to the above-mentioned metabolic pathways or to putative regulation proteins. Analyses of the genotypes of pMA5096-mediated mutants defective in biodegradation of poly(cis-1,4-isoprene) did not reveal homologues to recently identified genes coding for enzymes catalyzing the initial cleavage of poly(cis-1,4-isoprene). One rubber-negative mutant was disrupted in mcr, encoding an alpha-methylacyl-coenzyme A racemase. This mutant was defective in degradation of poly(cis-1,4-isoprene) and also of highly branched isoprenoid hydrocarbons.

Identification and cloning of genes encoding viomycin biosynthesis from Streptomyces vinaceus and evidence for involvement of a rare oxygenase

The tuberactinomycins are a family of basic cyclic peptides that exhibit potent antitubercular activity. These peptides are characterized by the presence of an amino acid with a 6-membered cyclic guanidine side chain (capreomycidine) and two or more 2,3-diaminopropionate residues. Viomycin (tuberactinomycin B) is a well-studied member of the family, was once prescribed for the treatment of tuberculosis, and has been shown to block translocation during protein biosynthesis. The gene cluster encoding viomycin biosynthesis was identified and cloned from Streptomyces vinaceus. The cluster was identified by screening genomic libraries with the viomycin phosphotransferase self-resistance gene (vph) and non-ribosomal peptide synthetase (NRPS) gene probes amplified from S. vinaceus genomic DNA. The viomycin cluster was localized to ca. 120 kb of contiguous DNA defined by four overlapping cosmid inserts. Each cosmid hybridized with one or more peptide synthetase gene probes and two also hybridized with vph. Confirmation that the cluster encoded viomycin biosynthesis was obtained from the disruption of two NRPS adenylation domains. Partial sequence analysis revealed an ORF (svox) predicted to encode a rare non-heme iron, alpha-ketoglutarate dependent oxygenase proposed to function in the oxidative cyclization of arginine to the capreomycidine residue. Insertional disruption of svox resulted in complete loss of viomycin production, confirming its involvement in the pathway.

Disruption of sblA in Streptomyces lividans permits expression of a heterologous alpha-amylase gene in the presence of glucose

In a transposition mutant of Streptomyces lividans TK24, the usually glucose-repressible expression of a heterologous alpha-amylase gene (aml) became resistant to glucose repression. The transposon had inserted into an ORF called sblA which encodes a 274 aa product sharing significant sequence similarities with various phosphatases that act on small phosphorylated substrates. sblA was transcribed as a monocistronic mRNA and its transcription was enhanced at the transition phase. Because its transcriptional and putative translational start points coincide, sblA is likely to be translated in the absence of a conventional RBS. The sblA-disrupted mutant is characterized by early growth arrest in glucose-grown cultures and by partial relief of glucose repression of aml expression.

Low target site specificity of an IS6100-based mini-transposon, Tn1792, developed for transposon mutagenesis of antibiotic-producing Streptomyces

To improve transposon mutagenesis of antibiotic-producing Streptomyces, a mini-transposon, Tn1792, was constructed, based on IS6100, originally isolated from Mycobacterium fortuitum. Easily manageable transposition assays were developed to demonstrate inducible transposition of Tn1792 into the Streptomyces genome from a temperature-sensitive delivery plasmid. Introduction of the selectable aac1 gene between the inverted repeats in Tn1792 allowed for both reliable identification of transposition events in Streptomyces, and also subsequent cloning of transposon-tagged sequences in Escherichia coli. This enabled the target site specificity of Tn1792 to be determined at nucleotide resolution, revealing no significant shared homology between different target sites. Consequently, Tn1792 is well suited for random mutagenesis of Streptomyces.

Transposon mutagenesis with IS6100 in the avermectin-producer Streptomyces avermitilis

The insertion sequence IS6100 was shown to undergo intermolecular transposition from a temperature-sensitive delivery plasmid to the genome of the avermectin-producer Streptomyces avermitilis, creating cointegrates. Evidence from both Southern hybridization and the range of auxotrophic mutations present in a transposon library was consistent with random transposition. It was not possible to increase transposase expression by readthrough transcription from a copy of the tipA promoter located adjacent to the insertion sequence. This was in part due to the absence of a homologue of the Streptomyces lividans transcriptional activator TipAL in S. avermitilis. However, recombinant S. avermitilis strains carrying the S. lividans tip operon were also deficient for induction of the promoter. The frequency of reversion of different auxotrophic mutations by precise excision, involving recombination across 8 bp direct repeats, was shown to vary by at least five orders of magnitude. This dependence of recombination frequency on chromosomal location may contribute to the stability of repetitive modular type I polyketide biosynthetic genes.

Molecular cloning and physical mapping of the daptomycin gene cluster from Streptomyces roseosporus

The daptomycin biosynthetic gene cluster of Streptomyces roseosporus was analyzed by Tn5099 mutagenesis, molecular cloning, partial DNA sequencing, and insertional mutagenesis with cloned segments of DNA. The daptomycin biosynthetic gene cluster spans at least 50 kb and is located about 400 to 500 kb from one end of the approximately 7,100-kb linear chromosome. We identified two peptide synthetase coding regions interrupted by a 10- to 20-kb region that may encode other functions in lipopeptide biosynthesis.

Two small linear plasmids of Streptomyces jumonjinensis

In a survey of plasmids in a variety of β-lactam antibiotic producing Streptomyces spp., two small linear plasmids (pSJL1 and pSJL2) of approximately 12 and 17.5 kb were detected within Streptomyces jumonjinensis NRRL 5741, in addition to the previously reported giant linear plasmids pSJL3 and pSJL4. Characterization of these plasmids by Southern hybridization indicated that no significant homology exists between the S. jumonjinensis plasmids and plasmids detected in other β-lactam antibiotic producing Streptomyces spp. Single and double restriction endonuclease digestions were performed to generate maps of the two plasmids. The plasmids pSJL1 and pSJL2 have copy numbers of 21–27 and 15–20, respectively.Key words: Streptomyces, linear plasmid, DNA hybridization, DNA homology.

Production of hybrid glycopeptide antibiotics in vitro and in Streptomyces toyocaensis

BACKGROUND

The glycopeptide antibiotics vancomycin and teicoplanin are currently the last line of defence against some microorganisms that are resistant to many drugs. The emergence of vancomycin-resistant and teicoplanin-resistant enterococci underscores the need for more potent antibiotics. The glycosylation patterns of glycopeptides and chemical modifications of the glycosyl moieties have been shown to greatly influence their antibiotic activity, and certain combinations have resulted in highly active new compounds. To explore further the production of more potent glycopeptide antibiotics, we assessed whether glycosyltransferases could be used to produce hybrid compounds that contain various combinations of sugars and peptide cores.

RESULTS

We cloned five glycosyltransferase genes from Amycolatopsis orientalis strains that produce vancomycin or a related glycopeptide, A82846. The gtfB and gtfE' genes from A. orientalis strains expressed in Escherichia coli produced glucosyltransferase activities that added glucose or xylose to the vancomycin heptapeptide. The GtfE' protein added glucose efficiently to two other heptapeptides related to teicoplanin to produce hybrid glycopeptide antibiotics. The cloned gtfE' gene, driven by the strong constitutive promoter ermEp*, was introduced into Streptomyces toyocaensis, which produces the antibiotic A47934, a heptapeptide related to teicoplanin; recombinant organisms produced glucosyl A47934, a hybrid glycopeptide antibiotic.

CONCLUSIONS

Cloned glycosyltransferases from glycopeptide antibiotic producers can be used to produce novel hybrid antibiotics, both in vitro and in vivo. Because similar enzymes have differing degrees of substrate specificity, it is advantageous to characterize the substrate specificity with enzymes expressed in E. coli prior to constructing recombinant actinomycetes for production.

Use of rpsL for dominance selection and gene replacement in Streptomyces roseosporus

We developed a gene replacement system using the rpsL gene of Streptomyces roseosporus and demonstrated its utility by constructing a deletion in the S. roseosporus glnA gene. A 1.3-kb BamHI fragment that hybridized to the Mycobacterium smegmatis rpsL gene was subcloned from an S. roseosporus cosmid library and sequenced. Plasmid pRHB514 containing the rpsL gene conferred streptomycin sensitivity (Sm(S)) to the Sm(r) S. roseosporus TH149. The temperature-sensitive plasmid pRHB543 containing rpsL and the S. roseosporus glnA gene disrupted with a hygromycin resistance (Hm(r)) gene was introduced into S. roseosporus TH149, and recombinants containing single and double crossovers were obtained after a temperature increase. Southern hybridization analysis revealed that single crossovers occurred in the glnA or rpsL genes and that double crossovers resulted in replacement of the chromosomal glnA gene with the disrupted glnA. Glutamine synthetase activity was undetectable in the recombinant containing the disrupted glnA gene.

Transposition mutagenesis in Streptomyces fradiae: identification of a neutral site for the stable insertion of DNA by transposon exchange

We explored transposition in Streptomyces fradiae (Sf) as a means to insert a second copy of the tylF gene to improve tylosin (Ty) production. Transposons Tn5096 and Tn5099 transposed relatively randomly in Sf, and many of the insertions caused no deleterious effects on Ty production yields. Tn5098, a derivative of Tn5096 containing tylF and tylJ genes, recombined into the chromosome into the tyl gene cluster and transposition was not observed. However, following the tagging of a neutral site (NS) by Tn5099 transposition, tylF was effectively inserted into the NS by homologous recombination (transposon exchange). Recombinants obtained by transposon exchange produced higher yields of Ty.

Repeated polyketide synthase modules involved in the biosynthesis of a heptaene macrolide by Streptomyces sp. FR-008

Genes for biosynthesis of a Streptomyces sp. FR-008 heptaene macrolide antibiotic with antifungal and mosquito larvicidal activity were cloned in Escherichia coli using heterologous DNA probes. The cloned genes were implicated in heptaene biosynthesis by gene replacement. The FR-008 antibiotic contains a 38-membered, polyketide-derived macrolide ring. Southern hybridization using probes encoding domains of the type I modular erythromycin polyketide synthase (PKS) showed that the Streptomyces sp. FR-008 PKS gene cluster contains repeated sequences spanning c. 105kb of contiguous DNA; assuming c. 5 kb for each PKS module, this is in striking agreement with the expectation for the 21-step condensation process required for synthesis of the FR-008 carbon chain. The methods developed for transformation and gene replacement in Streptomyces sp. FR-008 make it possible to genetically manipulate polyene macrolide production, and may later lead to the biosynthesis of novel polyene macrolides.

Hypertransposing derivatives of the streptomycete insertion sequence IS493

Transposons derived from the Streptomyces lividans insertion sequence IS493 are useful for the genetic analysis and manipulation of a number of Streptomyces spp. Tn5099-10, an IS493 derivative that contains a spontaneous deletion terminating in the left inverted repeat (IR-L), transposed at a 1000-fold higher frequency in Streptomyces griseofuscus, and at a tenfold higher frequency in Streptomyces fradiae, than the IS493 derivatives, Tn5096 and Tn5099. The IR-L from Tn5099-10 was used to construct a cassette which hypertransposes from plasmids containing the transposon genes, ORFA and ORFB, outside of the inverted repeats. The target sequences of two Tn5099-10 insertions conformed to the consensus target sequence of the other IS493 derivatives, gNCaNTgNNy (where lower-case letters indicate that other nt have been observed at this position and N is any nt). Transposition mutant libraries of S. griseofuscus and S. fradiae can be easily prepared in broth culture by using the hypertransposing elements and a temperature-sensitive delivery plasmid.

Conjugal transfer of cosmid DNA from Escherichia coli to Saccharopolyspora spinosa: effects of chromosomal insertions on macrolide A83543 production

Cosmid pOJ436, containing large inserts of Saccharopolyspora spinosa (Ss) DNA, was transferred by conjugation from Escherichia coli to Ss an integrated into the chromosome, apparently by homologous recombination, at high frequencies (10(-5) to 10(-4) per recipient). Transfer was mediated by the plasmid RP4 (RK2) transfer functions in E. coli, and the RK2 oriT function located on pOJ436 [Bierman et al., Gene 116 (1992) 43-49]. pOJ436 lacking Ss DNA, or containing a small insert (approx. 2 kb) of Ss DNA, conjugated from E. coli and integrated at either of two bacteriophage phi C31 attB sites at low frequency (approx. 10(-7) per recipient). Exconjugants containing homologous inserts or inserts at the phi C31 attB sites were stable in the absence of antibiotic selection, and most produced control levels of tetracyclic macrolide A83543 factors. Some exconjugants contained similar kinds of large deletions and were defective in macrolide production.

The genetic basis of precursor supply for the biosynthesis of macrolide and polyether antibiotics

Macrolide and polyether biosynthesis in actinomycetes is regulated at the level of precursor supply by effects of nutrients on the sources of the low-molecular-weight fatty acids used to build the carbon framework of these antibiotics. Ammonium ion appears to suppress the first enzymes of valine and threonine catabolism and also inhibits their activity. Disruption of the valine dehydrogenase (vdh) gene of Streptomyces coelicolor destroys its ability to grow on branched-chain amino acids as the sole nitrogen source in a minimal medium but has no effect on the biosynthesis of the acetate-derived antibiotic, actinorhodin. Expression of the vdh gene is repressed by > 25 mM ammonium ion or glucose but not by valine, glycerol, or maltose. Vdh enzyme activity is stimulated by valine induction. These results suggest that the inhibition of valine catabolism by ammonium and/or glucose could explain why macrolide production is inhibited by ammonium ion.

Glucose kinase has a regulatory role in carbon catabolite repression in Streptomyces coelicolor

A glucose kinase (glkA) mutant of Streptomyces coelicolor A3(2) M145 was selected by the ability to grow in the presence of the nonmetabolizable glucose analog 2-deoxyglucose. In this glkA mutant, carbon catabolite repression of glycerol kinase and agarase was relieved on several carbon sources tested, even though most of these carbon sources are not metabolized via glucose kinase. This suggests that catabolite repression is not regulated by the flux through glucose kinase and that the protein itself has a regulatory role in carbon catabolite repression. A 10-fold overproduction of glucose kinase also results in relief of catabolite repression, suggesting that excess glucose kinase can titrate the repressing signal away. This could be achieved directly by competition of excess glucose kinase with its repressing form for binding sites on DNA promoter regions or indirectly by competition for binding of another regulatory protein.

Transposon mutagenesis by Tn4560 and applications with avermectin-producing Streptomyces avermitilis

The Tn3-like Streptomyces transposon Tn4560 was used to mutagenize Streptomyces avermitilis, the producer of anthelmintic avermectins and the cell growth inhibitor oligomycin. Tn4560 transposed in this strain from a temperature-sensitive plasmid to the chromosome and from the chromosome to a plasmid with an apparent frequency of about 10(-4) to 10(-3) at both 30 and 39 degrees C. Auxotrophic and antibiotic nonproducing mutations were, however, obtained only with cultures that were kept at 37 or 39 degrees C. About 0.1% of the transposon inserts obtained at 39 degrees C caused auxotrophy or abolished antibiotic production. The sites of insertion into the S. avermitilis chromosome were mapped. Chromosomal DNA fragments containing Tn4560 insertions in antibiotic production genes were cloned onto a Streptomyces plasmid with temperature-sensitive replication and used to transport transposon mutations to other strains, using homologous recombination. This technique was used to construct an avermectin production strain that no longer makes the toxic oligomycin.

Plasmid cloning vectors for the conjugal transfer of DNA from Escherichia coli to Streptomyces spp

We have constructed cloning vectors for the conjugal transfer of DNA from Escherichia coli to Streptomyces spp. All vectors contain the 760-bp oriT fragment from the IncP plasmid, RK2. Transfer functions need to be supplied in trans by the E. coli donor strain. We have incorporated into these vectors selectable antibiotic-resistance markers (AmR, ThR, SpR) that function in Streptomyces spp. and other features that should allow for: (i) integration via homologous recombination between cloned DNA and the Streptomyces spp. chromosome, (ii) autonomous replication, or (iii) site-specific integration at the bacteriophage phi C31 attachment site. Shuttle cosmids for constructing genomic libraries and bacteriophage P1 cloning vector capable of accepting approx. 100-kb fragments are also described. A simple mating procedure has been developed for the conjugal transfer of these vectors from E. coli to Streptomyces spp. that involves plating of the donor strain and either germinated spores or mycelial fragments of the recipient strain. We have shown that several of these vectors can be introduced into Streptomyces fradiae, a strain that is notoriously difficult to transform by PEG-mediated protoplast transformation.

Reconstruction of a Streptomyces linear replicon from separately cloned DNA fragments: existence of a cryptic origin of circular replication within the linear plasmid

We report here the reconstruction of a functional linear replicon, the 12-kilobase Streptomyces clavuligerus plasmid pSCL, from separate DNA fragments cloned in Escherichia coli on the pUC19 plasmid. Protein-free DNA molecules containing the full-length pSCL sequence, an internally inserted thiostrepton-resistance gene, and adventitious nucleotides external to the pSCL termini were introduced into Streptomyces lividans, where the synthesis and functional attachment of replication proteins occurred and pSCL was established as an extrachromosomal linear replicon. Transformation of S. lividans with uncut supercoilded pUC19/pSCL DNA from E. coli or with a circularized 8-kilobase internal fragment of pSCL yielded circular replicons, indicating the existence of a cryptic origin of circular replication within the linear plasmid. Insertion mutations at sites that prevented the replication of pSCL linear plasmids also interfered with its replication in the circular mode.

Transposition of Tn5096 and related transposons in Streptomyces species

IS493 is an insertion sequence isolated from Streptomyces lividans by a method designed to 'trap' transposable elements. IS493 was converted to functional transposons by cloning antibiotic-resistance-encoding genes between ORF-A and ORF-B of IS493 or near the left-end inverted repeat of the element. Tn5096 transposed relatively randomly in several Streptomyces species. Tn5096 can be introduced into streptomycetes on temperature-sensitive vectors by protoplast transformation, FP43-mediated transduction, or by conjugation from Escherichia coli. We have shown that additional genes can be inserted in Tn5096 without disrupting transposition, and that Tn5096 insertions in a tylosin (Ty)-producing strain of Streptomyces fradiae frequently cause no deleterious effects on Ty production. A promoter probe transposon, Tn5099, containing a promoterless xylE gene, transposed in Streptomyces griseofuscus and S. fradiae, and transcriptional fusions were readily identified.

Tn5099, a xylE promoter probe transposon for Streptomyces spp

Tn5099, a promoter probe transposon for Streptomyces spp., was constructed by inserting a promoterless xylE gene and a hygromycin resistance gene into IS493. Tn5099 transposed into different sites in the Streptomyces griseofuscus genome, and the xylE reporter gene was expressed in some of the transposition mutants. Strains containing Tn5099 insertions that gave regulated expression of the xylE gene were identified.

Transposition of Tn5096 from a temperature-sensitive transducible plasmid in Streptomyces spp

Transposon Tn5096 was inserted into a derivative of the temperature-sensitive plasmid pMT660 containing the bacteriophage FP43 pac site. The resulting plasmid, pRHB126, was transduced by FP43 into several Streptomyces species. Tn5096 transposed from pRHB126 into different sites in the genomes of Streptomyces ambofaciens, Streptomyces cinnamonensis, Streptomyces coelicolor A3(2), Streptomyces fradiae, Streptomyces griseofuscus, and Streptomyces thermotolerans.

Transposition and transduction of plasmid DNA inStreptomyces spp

To expand the application of molecular genetics to many different streptomycete species, we have been developing two potentially widely applicable methodologies: transposon mutagenesis and plasmid transduction. We constructed three transposons from the Streptomyces lividans insertion sequence IS493. Tn5096 and Tn5097 contain an apramycin resistance gene inserted in different orientations between the two open reading frames of IS493. These transposons transpose from different plasmids into many different sites in the Streptomyces griseofuscus chromosome and into its resident linear plasmids. Tn5099 contains a promoterless xylE gene and a hygromycin-resistance gene inserted in IS493 close to one end. Tn5099 transposes in S. griseofuscus giving operon fusions in some cases that drive expression of the xylE gene product, catechol deoxygenase, giving yellow colonies in the presence of catechol. We have also developed plasmid vectors that can be transduced into many streptomycete species by bacteriophage FP43. We describe the characterization of FP43 and mapping of several bacteriophage functions. The region of cloned FP43 DNA essential for plasmid transduction includes the origin for headful packaging.

Properties of the streptomycete temperate bacteriophage FP43

FP43 is a temperate bacteriophage for Streptomyces griseofuscus that forms plaques on many Streptomyces species. FP43 virions contain 56 kb of double-strand DNA that is circularly permuted and terminally redundant, and contains 65% G + C. A physical map of the FP43 genome was constructed, and the origin for headful packaging (pac) was localized to an 8.8-kb region of the genome (hft) that mediates high-frequency transduction by FP43 of plasmid pRHB101. The phage attachment site (attP), a replication origin (rep), a region that inhibits plaque formation (pin), and a 3-kb deletion (rpt) that caused a 100-fold reduction in plasmid transduction were mapped.