Determination of methylenomycin A synthesis by the pSV1 plasmid from Streptomyces violaceus-ruber SANK 95570

A plasmid (pSV1) of 110 x 10(6) daltons from a methylenomycin A producing strain of Streptomyces violaceus-ruber was detected on an isolated from agarose gels. Elimination of this plasmid by protoplasting and regeneration resulted in the simultaneous loss of methylenomycin A production and resistance. pSV1 hybridized with pBR322 containing a cloned fragment of 1.7 x 10(6) daltons from S. coelicolor A3(2) which codes for methylenomycin A resistance. The pSV1 plasmid could be transferred to S. lividans by conjugation and by transformation and plasmid DNA identical in size to pSV1 could be isolated from the recipient strains. These experiments show that pSV1 codes for methylenomycin A production and resistance, in close analogy to the SCP1 plasmid from S. coelicolor A3(2).

Plasmid loss and changes within the chromosomal DNA of Streptomyces reticuli

The sporulating wild-type strain of Streptomyces reticuli, which produces a melanin pigment and the macrolide leucomycin, contains plasmid DNA of 48 to 49 megadaltons. Plasmidless variants had an altered secondary metabolism and a changed antibiotic resistance pattern. By using a new colony hybridization technique developed for streptomycetes, it could be shown that plasmidless variants could be transformed with the wild-type plasmid DNA, which, however, is quickly lost from regenerated mycelium. In contrast to the wild-type strain, the plasmidless variants contain amplified nucleotide sequences within the chromosomal DNA. The number and size of these sequences vary with the strain tested. Hybridization studies revealed that the reiterated sequences are neither amplified ribosomal nor plasmid genes, but are present in small concentrations within the wild-type chromosome. Some of them share extensive homologies with each other and are located at different positions within the chromosome. It is assumed that alterations in secondary metabolism are due to changes within both the chromosomal and the extrachromosomal DNAs of S. reticuli.

[Physical mapping of actinophage Streptomyces coelicolor A3(2). VI. The use of deletion mutants of actinophage phi C31 for construction of phage vectors]

Nonessential region responsible for G function has been identified in theta C31 phage genome by means of deletion mutants. The mutant phenotype is expressed upon theta C31 phage propagation in Streptomyces albus G strains differing in functioning of restriction and modification systems. Based on their increased resistance to EDTA, deletions were located in theta C31 delta 10 and theta C31 delta 65 phage mutants. Data are presented on physical mapping of nonessention region of theta C31 phage. The total length of this region is 24.1% of the overall length of DNA molecules. The DNA segment of 19.1% of the whole genome contains overlapped deletions. Theta C31 actinophage is proposed to be used as a cloning vector for Streptomyces. Various deletion mutants obtained, with the capacity of about 3 thousands base pairs may serve as "insertion vectors". The presence of the stretched nonessential genome region allows to use theta C31 phage as a "replacement vector". Then, insertion of foreign DNA to replace the EcoRI--C fragment of theta C31 DNA of 6.4 x 10(3) base pairs is possible. The phages comprising hybrid molecules may be selected for G and Lyg phenotypes.

The expression of Streptomyces and Escherichia coli drug-resistance determinants cloned into the Streptomyces phage phi C31

Lysogens obtained by infecting Streptomyces albus G with a phi C31-pBR322 chimaeric prophage or its delta W12 deletion derivative had increased tetracycline resistance. The ability of the delta W12 derivative to transduce tetracycline resistance was inactivated by inserting a viomycin resistance determinant (vph) into the BamHI site of the pBR322 tet gene, and restored by excising the vph gene. Another deletion mutant (delta W17) of the chimaera, carrying an intact tet gene, was normally unable to transduce tetracycline resistance. This inability was correlated with the finding, by Southern hybridisation analysis, that the att site required for insertion of phi C31 prophage into the host chromosome was located within the delta W17 deletion. Use of phi C31 lysogenic recipient permitted the integration of the att-deleted phage, presumably by homologous recombination, giving tetracycline-resistant double lysogens. This technique was extended to S. coelicolor A3(2) in the detection of derivatives of the att-deleted phage into which a thiostrepton-resistance determinant (tsr) had been inserted in vitro. Phage released from double lysogens were mainly recombinants. One such recombinant is a PstI vector for DNA cloning, able to accommodate up to 6 kb of introduced DNA.

Reiterated DNA sequences in a mutant strain of Streptomyces glaucescens and cloning of the sequence in Escherichia coli

Streptomyces glaucescens exhibits a high degree of genetic instability. A sequence of 7.2 kb has been found which is present in a few tandemly repeated copies in the wild type strain GLA 0 and is amplified to ca. 500 copies per genome in the mutant strain GLA 1204. This sequence was cloned in Escherichia coli using pBR325 as vector.

Cloning and expression of a Streptomyces fradiae neomycin resistance gene in Escherichia coli

A Streptomyces fradiae DNA sequence, which codes for a neomycin phosphotransferase, has been subcloned from the Streptomyces recombinant plasmid pIJ2 [a chimera between the Streptomyces plasmid SLP1.2 and chromosomal DNA containing a neomycin (Nm) resistance gene] into the BamHI restriction enzyme site of pHV14. Three different recombinant plasmids (pWHR1, pWHR2, pWHR3) have been isolated which transform Escherichia coli to Nm resistance. Southern transfer hybridization experiments show that the recombinant plasmids contain the cloned Streptomyces Nm resistance gene, and lysates of E. coli containing the recombinant plasmids were shown to have Nm phosphotransferase activity, demonstrating that a gene from Streptomyces can be expressed in E. coli.

Protoplast fusion permits high-frequency transfer of a Streptomyces determinant which mediates actinomycin synthesis

Prototrophic recombinants and heterocaryotic colonies developed at high frequency when protoplasts of nutritionally complementary actinomycin-producing and nonproducing strains of Streptomyces antibioticus were fused in the presence of polyethylene glycol and plated on minimal regeneration medium. Of the spores obtained from aerial hyphae of a single heterocaryotic colony, 99% carried the act+ character regardless of whether the nutritional markers of the spore were derived from the act+ or the act parent. Similarly, a high-frequency transfer (68% in S. antibioticus, 48% in Streptomyces parvulus) of act+ determinant(s) to act was achieved by protoplast fusion. Protoplasts of a doubly auxotrophic act strain of S. parvulus were efficiently transformed in the presence of polyethylene glycol with respect to the auxotrophic markers by DNA of an act+ auxotrophic strain with complementary nutritional requirements. The transformation frequency of the nutritional (chromosomal) markers was 17%. In contrast, the transformation frequency for actinomycin synthesis was less than 1%.

Isolation and characterization of covalently closed circular DNA associated with chromosomal and membrane fraction from Streptomyces ambofaciens

Covalently closed circular (ccc) DNAs were isolated by a technique involving alkaline denaturation from the spiramycin producer Streptomyces ambofaciens KA-1028 and also from spiramycin non-producing strains AF-11 and QN-25; plasmids could not be detected in these strains by a cleared lysate method. It was found that most of the ccc DNA in these strains was present in the chromosomal and membrane fractions. These ccc DNAs had identical mobilities in agarose gel electrophoresis. The size was calculated to be 53.1 x 10(6) daltons from the contour length measurements. The ccc DNA gave one fragment on digestion with Hind III, three fragments with Eco R1, and twenty-eight fragments with Bam H1.

pIJ101, a multi-copy broad host-range Streptomyces plasmid: functional analysis and development of DNA cloning vectors

Streptomyces lividans ISP 5434 contains four small high copy number plasmids: pIJ101 (8.9 kb), pIJ102 (4.0 kb), pIJ103 (3.9 kb) and pIJ104 (4.9 kb). The three smaller species appear to be naturally occurring deletion variants of pIJ101. pIJ101 and its in vivo and in vitro derivatives were studied after transformation into S. lividans 66. pIJ101 was found to be self-transmissible by conjugation, to elicit "lethal zygosis" and to promote chromosomal recombination at high frequency in both S. lividans 66 and S. coelicolor A3(2). A restriction endonuclease cleavage map of pIJ101 was constructed for 11 endonucleases; sites for five others were lacking. Many variants of pIJ101 were constructed in vitro by inserting DNA fragments determining resistance to neomycin, thiostrepton or viomycin, and having BamHI termini, into MboI or BclI sites on the plasmid, sometimes with deletion of segments of plasmid DNA. The physical maps of these plasmids were related to their phenotypes in respect of lethal zygosis and transfer properties. In vivo recombination tests between pairs of variant plasmids were also done. These physical and genetic studies indicated that determinants of conjugal transfer occupy less than 2.1 kb of the plasmid. A second segment is required for spread of the plasmid within a plasmid-free culture to produce the normal lethal zygosis phenotype: insertion of foreign DNA in this region caused a marked reduction in the diameter of lethal zygosis zones. The minimum replicon was deduced to be 2.1 kb or less in size; adjacent to this region is a 0.5 kb segment which may be required for stable inheritance of the plasmid. The copy number of several derivatives of pIJ101 in S. lividans 66 was between 40 and 300 per chromosome and appeared to vary with the age or physiological state of the culture. pIJ101 derivatives have a wide host range within the genus Streptomyces: 13 out of 18 strains, of diverse species, were successfully transformed. Knowledge of dispensable DNA segments and the availability of restriction sites for the insertion of DNA, deduced from the properties of plasmids carrying the E. coli plasmid pACYC184 introduced at various sites, was used in the construction of several derivatives of pIJ101 suitable as DNA cloning vectors. These were mostly designed to be non-conjugative and to carry pairs of resistance genes for selection. They include a bifunctional shuttle vector for E. coli and Streptomyces; a Streptomyces viomycin resistance gene of this plasmid is expressed in both hosts.

Partial characterization of a small, multiple-copy plasmid from Streptomyces espinosus and the derivation of a high copy-number deletion mutant

An organism classified as Streptomyces espinosus was found to carry an approx. 9.2-kb plasmid. This plasmid, designated pUC6, has a copy number of 30-40 per host genome equivalent. Plasmid pUC1061, a copy-number mutant of pUC6, was isolated after in vitro deletion of an approx. 2.0-kb XhoI restriction fragment. Plasmid pUC1061 has a copy number of 500-600. Plasmid pUC1061 appears to be incompatible with pUC6 and will transform a pUC6-containing culture at a frequency of approx. 1%. The sizes, restriction maps and copy numbers of plasmids pUC6 and pUC1061 indicate these may be valuable vectors for gene cloning Streptomyces.

Genetic and biochemical features of spiramycin biosynthesis in Streptomyces ambofaciens--curing, protoplast regeneration and plasmid transfer

Spiramycin-producing Streptomyces ambofaciens KA-1028 harboring the pSA1 plasmid gave rise to spiramycin non-producing variants at high frequencies by various curing treatments. However, a number of the spiramycin non-producing progeny obtained by treatment with acridine dyes, still harbored plasmid DNAs which could not be differentiated from plasmid pSA1 by contour length, cleavage patterns and heteroduplex analysis. By treatment with mitomycin C, plasmid pSA1 was cured at high efficiency and spiramycin non-producing strains were obtained. Strain U-1717R obtained by regeneration of protoplasts of plasmid-cured strain U-1717 regained spiramycin production on growth on solid medium only. Furthermore, transconjugants obtained by mating between strain KA-1028 and U-1717R-24 (streptomycin-resistant) regained spiramycin production in both liquid and solid media. We conclude that the genes for the biosynthesis of spiramycin are encoded in a replicon other than plasmid pSA1 but that this plasmid plays a role in the regulation of spiramycin production.

Plasmid DNA in the erythromycin producing microorganism, Streptomyces erythreus NRRL 2338

Streptomyces erythreus NRRL 2338, the erythromycin producing microorganism, contains extrachromosomal (plasmid) DNA. Four different plasmids, pSE1, pSE2, pSE4 and pSE6 present in the wild-type strain have characteristic mobilities on agarose gel electrophoresis, molecular weight and restriction endonuclease digestion patterns. Treatment of the wild-type strain with ethidium bromide or acridine orange gave two variants, one that could not convert erythronolide B to 3 (alpha)-mycarosylerythronolide B and another than produced 2 approximately 3 times more erythromycin A than the parental strain. Although the plasmid DNA profile of these two variants is different from the wild-type strain, it is not possible to conclude that any of the structural genes for erythromycin biosynthesis are located on the plasmids of S. erythreus NRRL 2338.

Isolation and characterization of Streptomyces fradiae plasmids which are prophage of the actinophage phiSF1

Two plasmids, designated pUC1 and pUC13, have identified as different prophage states of the Streptomyces fradiae actinophage phiSF1. Plasmids pUC1 and pUC13, 51.1 Md, are identical as determined by restriction endonuclease analysis and other criteria. They differ in that while pUC1 specifies "type A" plaques, characterized by a narrow zone of growth inhibition around a transformant colony, pUC13 specifies "type B" plaques, characterized by concentric rings of growth and growth inhibition around a transformant colony. Additionally cultures carrying pUC13 release antinophage phiSF1 at a frequency about 10 3-10 4 times that pUC1 containing cultures. Restriction enzyme digestion, transfection, and transformation analyses show that phiSF1 DNA, 55.7 Md, is about 8-10% larger than pUC13 and appears to be circularly permuted and terminally redundant. The pUC1 and pUC13 prophage are interconvertible.

[Genetic instability of the production of antibiotic substances controlled by the SCP2 plasmid of Streptomyces coelicolor A3(2)]

Streptomyces coelicolor A3(2) strain bearing a variant of SCP2 plasmid produces three antibiotic substances: amromycin and streptocins A and B. After growth at elevated temperature (37 degrees C) of S. coelicolor A3(2), mutants which are not capable of producing amromycin and streptocins A and B (ant- mutants) were formed at high frequency (50%). These mutants retained SCP2 plasmid. Genetic analysis demonstrates that Ant phenotype is caused by a mutation in SCP2 plasmid. Genetic analysis demonstrates that Ant phenotype is caused by a mutation in SCP2. Heteroduplex and electrophoretic analysis of SCP2 DNAs from mutant variants indicates that these plasmids contained the identical deletion of 800 +/- 100 base pairs, as compared to SCP2 DNA of the initial strain. Ant variants revert to the initial phenotype at a frequency of 1.10(-2) to 1.10(-3). In turn, revertants from Ant variants a high frequency, similar to the initial strain. It is suggested that reversible Ant+ in equilibrium or formed from Ant- transitions might be the result of transposition of a genetic element in SCP2 controlling production of amromycin and streptocins A and B.

Fusion of protoplasts of Streptomyces lavendulae

Protoplasts of two different auxotrophic mutants of Streptomyces lavendulae were fused with polyethylene glycol (PEG) 1,000, and allowed to regenerate on selective media. Prototrophic colonies overwhelmed other types of recombinants on any selective media. These prototrophic strains were stable after successive isolation. These results suggest that stable diploid cells were formed by cell fusion, which differed from the case of S. coelicolor.

[Mutagenesis in Streptomycete cultures exposed to bleomycin]

Mutagenic properties of bleomycin, an antitumor antibiotic were studied with respect to 2 species of streptomycetes producing practically important antibiotics. A multifold increase in the frequency of prototrophic revertants among the survivors of strains His- and Met- of Actinomadura carminata exposed to bleomycin was observed. Bleomycin was effective in induction of various morphological mutants, and auxotrophs at a high survival rate of the spores of Str. cremeus var. tobramycini, a tobramycin-producing organism. It was shown with the method of subsequent mutagenesis that the efficacy of induction of morphological and auxotrophic mutants in germinating spores of Actinomadura carminata, a carminomycin-producing organism by bleomycin in a concentration of 100 micrograms/ml and an exposure time of 5 minutes was much higher that in the latent spores. The mutagenic effect of bleomycin is comparable with that of ionizing radiation.

Secretion of tyrosinase in Streptomyces glaucescens

In Streptomyces glaucescens, the intracellular and the extracellular enzyme forms of tyrosinase were found to be indentical in molecular weight (29 000), in copper content (0.21%), in the 19 amino acids at the amino-terminal end and in the ratio of cresolase to catecholase activity (0,005). The tyrosinase secretion process exhibited a constant rate of 0.15 units h-1 (mg protein)-1. Under highly induced conditions intracellular tyrosinase was accumulated. Mutations responsible for the non-melanogenic, tyrosinase-positive non-secretor mutant type are located chromosomally on the upper right arc of the S. glaucescens map near the ade-1 marker.

Effect of l-valine and l-isoleucine on fatty acid composition of Streptomyces hygroscopicus and S. griseus

The effects of L-valine and L-isoleucine on the composition of mycelial fatty acids were investigated during growth of differentiating parent strains of Streptomyces hygroscopicus and Streptomyces griseus as well as their non-differentiating derivatives (Amy-strains) on a synthetic medium. Both in the Amy+ and Amy- strains, in the presence of L-valine, the portion of the isopalmitic acid (iC16:0) increased, but the addition of L-isoleucine led to an elevated level of the 12-methyltetradecanoic acid (aC15:0). The results suggest that the genetically determined alterations in the ratio of both fatty acids in the non-differentiating derivatives may be due to specific changes in the biosynthetic pathways of both amino acid precursors rather than due to changes of their catabolism.

Production of glucose isomerase by genus Streptomyces

Screening for glucose isomerases was done using 46 species and 63 strains of Streptomyces type cultures. Glucose isomerase was found in a wide range of these species. The intracellular glucose isomerase of S. olivochromogenes showed the highest fructose conversion ratio. The apparent extracellular glucose isomerase activities were observed for several strains of Streptomyces, Streptomyces venezuelae had the highest apparent extracellular glucose isomerase activity. The glucose isomerase yield was improved from 1.95 units/ml to 7.5 units/ml by induced mutation and culturing condition studies. This increase in glucose isomerase yield has made it possible to produce glucose isomerase industrially.

Genetic stability of differentiated functions in Streptomyces hygroscopicus in relation to conditions of continuous culture

The genetic stability of the capacity of an improved strain of Streptomyces hygroscopicus to produce the macrolide antibiotic turimycin was investigated during long-term continuous culture. Dilution rate, growth-limiting substrate and culture temperature were varied. Certain culture conditions resulted in the stable propagation of the inoculated turimycin-producing population. Other conditions led to segregation of the initial population. Turimycin non-producing phenotypes appeared, and in each case the simultaneous loss of ability to form aerial mycelium was observed. The non-differentiating clones were found to be stable, without any reversion to the parental phenotype, indicating that a loss of genetic information probably took place.

Excision of chromosomal DNA sequences from Streptomyces coelicolor forms a novel family of plasmids detectable in Streptomyces lividans

When strains of Streptomyces coelicolor A3(2) lacking the previously identified autonomous plasmids SCP1 and SCP2 are crossed with Streptomyces lividans 66, some of the S. lividans progeny are able to elicit zones of growth inhibition (lethal zygosis), previously associated with the transfer of conjugative Streptomyces plasmids, when grown in contact with S. lividans 66. Some such progeny yield covalently closed circular (CCC) plasmid DNA, the size and restriction endonuclease cleavage pattern of which is constant for a particular isolate, but varies among isolates. These plasmids, which have been named SLP1.1, SLP1.2, etc., all confer resistance to lethal zygosis elicited by the others. Genetic and molecular characterization of the plasmids reveals that they are derived from the strA region of the chromosome of S. coelicolor. It is proposed that, before or during mating with S. lividans, the SLP1 sequences are excised from the chromosome, bringing varying regions of the surrounding chromosome with them, and can circularize to yield the SLP1 family of plasmids. Autonomous SLP1 plasmids can also be generate by cleaving total DNA of S. coelicolor with certain restriction enzymes, ligating it, and transforming the DNA into S. lividans. The autonomous SLP1 plasmids exist within S. lividans in a few copies per chromosome, and act as fertility factors. They provide suitable vectors for DNA cloning since the segments of chromosomal DNA carried by the larger members of the family are dispensable.

[Restriction mapping of plasmid pSa1, isolated from Streptomyces albus G strain]

A novel plasmid designated pSa1 has been isolated from Streptomyces albus G strain producing SalGI restriction endonuclease. Molecular weight of the plasmid is 3.4 +/- 0.2 mD. The action of 12 restriction endonucleases on the plasmid DNA was studied. Restriction map of pSa1 DNA was established for SmaI, HindII, XbaI and KpnI endonucleases.

Protoplast fusion in Streptomyces: conditions for efficient genetic recombination and cell regeneration

Protoplasts from four different species of Streptomyces regenerated cells efficiently in hypertonic soft agar medium overlaid on partially dehydrated regeneration medium. The efficiencies of regeneration were strongly dependent upon the incubation temperatures for cell growth and for protoplast regeneration. Cell growth temperatures (before protoplast formation) required for efficient protoplast regeneration varied from species to species, and did not necessarily correlate with the optimum temperatures for protoplast regeneration. Under the best conditions, protoplasts from all four species were able to regenerate viable cells at nearly 100% efficiency and also formed confluent lawns of mycelia when plated in high concentrations. The temperatures for cell growth and protoplast regeneration also affected the frequencies of genetic recombinants obtained by protoplast fusion in S. fradiae, and highest recombinant frequencies were obtained under conditions which favoured efficient protoplast regeneration. With the modified procedure described, maximum frequencies of genetic recombinants were obtained by treating parental protoplasts with 40 to 60% polyethylene glycol 1000.

Expression of the Streptomyces enzyme endoglycosidase H in Escherichia coli

Endoglycosidase H is one of a large number of enzymes secreted by Streptomyces plicatus and other Streptomyces species. When the structural gene for this enzyme is introduced into Escherichia coli attached to the plasmid pBR-322 or Charon 4 phage, the enzyme is synthesized and is found in the periplasmic space, culture medium, and cells. Attachment of the UV-5 lac promoter to a site in the plasmid adjacent to the Streptomyces insert stimulates enzyme synthesis as much as 100-fold. This result demonstrates that transcription of the Streptomyces gene can be initiated from sequences outside of the Streptomyces insert. Initiation of transcription on a Streptomyces promoter is also a suggested but unproven possibility. In contrast to the situation in Streptomyces, where the enzyme has a molecular weight of 27,000, the enzyme made in E. coli has a molecular weight of approximately 30,000. Possible explanations for this difference in size are lack of cleavage of the Streptomyces secretion "signal sequence" in E. coli or protein "processing" by enzymes secreted into the medium by STreptomyces.

Properties of S-adenosyl-L-methionine:macrocin O-methyltransferase in extracts of Streptomyces fradiae strains which produce normal or elevated levels of tylosin and in mutants blocked in specific O-methylations

An efficient assay for S-adenosyl-L-methionine:macrocin O-methyltransferase, the enzyme which carries out the terminal step in tylosin biosynthesis, is described. Macrocin O-methyltransferase requires Mg2+ and S-adenosyl-L-methionine for activity, has a temperature optimum of about 31 degrees C, and has a pH optimum of 7.5 to 8.2. Macrocin O-methyltransferase specifically converts macrocin to tylosin by O-methylation of the 3" ' position of macrocin. In vitro methylation studies with extracts from a tylosin-producing Streptomyces fradiae strain and from mutant strains blocked in 2" '- or 3" '-O-methylations indicated that: (i) the 2" '- and 3" '-O-methylations occur after 6-deoxy-D-allose is attached to the macrolide ring; (ii) the 2" '- and 3" '-O-methylations are carried out by separate enzymes; and (iii) the 2" '-O-methylation precedes the 3" '-O-methylation. Macrocin O-methyltransferase was inhibited by high levels of its substrate, macrocin, by its product, tylosin, and by other tylosin analogs which contained mycinose or demethyl analogs of mycinose. Macrocin O-methyltransferase was produced early in the tylosin fermentation cycle by S. fradiae and preceded the onset of rapid tylosin biosynthesis by about 24 h. The enzyme specific activity reached maximum at about 72 h and then slowly declined. A mutant strain of S. fradiae selected for increased tylosin production synthesized macrocin O-methyltransferase more rapidly and accumulated a higher enzyme specific activity than a wild-type strain.

New anthracycline metabolites from mutant strains of Streptomyces galilaeus MA144-M1. II. Structure of 2-hydroxyaklavinone and new aklavinone glycosides

Four blocked mutants of aclacinomycin-producing Streptomyces galilaeus MA144-M1 produced new anthracyclinones; 2-hydroxyaklavinone, its non-esterified analog and 2-hydroxy-7-deoxyaklavinone, several new anthracyclines; 2-deoxyfucosyl-2-deoxyfucosyl-rhodosaminylaklavinone (MA144 U1), 2-deoxyfucosyl-rhodosaminylaklavinone (MA144 U2) and five aklavinone glycosides devoid of amino sugar, designated as MA144 U5, U6, U7, U8 and U9.

Restriction mapping of the DNA of the Streptomyces temperate phage phi C31 and its derivatives

DNA of phi C31 propagated on Streptomyces lividans 66 contained no sites for the restriction enzymes BamHI, SalPI (=PstI) and XhoI; one for XbaI; three for HpaI; five for ClaI and KpnI; six for EcoRI; about 13 for HindIII; about 14 for BclI; and more than 15 for FspAI, HgiAI, SacI, SalGI and SmaI. A complete map of 20 sites (XbaI, HapI, ClaI, KpnI and EcoRI) was obtained using partial digestion and double digestion of DNA of the wild-type and deletion and insertion mutants. The total molecular size was estimated to be 41.2 kb.

Properties of Streptomyces fradiae mutants blocked in biosynthesis of the macrolide antibiotic tylosin

We isolated numerous mutants of Streptomyces fradiae blocked in tylosin biosynthesis after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. These mutants were classified into nine groups, based upon the tylosin-like compounds produced and upon cofermentation analyses. More than 80% of the mutants isolated produced no tylosin-like compounds, and the majority of these were blocked only in the formation of tylactone. Four classes of mutants blocked in the biosynthesis or addition of tylosin sugars were isolated; tylA mutants were blocked in the formation of all three tylosin sugars, whereas tylB, tylC, and tylD mutants were blocked specifically in the biosynthesis or the addition of mycaminose, mycarose, and 6-deoxy-d-allose, respectively. Two classes of mutants (tylH and tylI) blocked in specific oxidations of tylactone and two classes (tylE and tylF) blocked in specific O-methylations of demethylmacrocin and macrocin were also characterized. Cofermentation and bioconversion studies with these mutants suggested the following relationships: (i) the tylosin sugars are derived from a common intermediate; (ii) tylactone is the first intermediate which can be excreted in appreciable quantities; (iii) the addition of mycaminose to the C-5 hydroxyl group of tylactone must precede oxidations at C-20 and C-23; (iv) oxidation at C-20 normally precedes the attachment of mycarose to the 4' hydroxyl position of mycaminose; and (v) 6-deoxy-d-allose is added to the C-23 hydroxyl position of the lactone and subsequently O-methylated at 2''' and 3''' positions. The O-methylations appear to be the final two steps in tylosin biosynthesis, and the 2''' O-methylation must occur before the 3''' O-methylation can take place. All of the tyl mutants except the tylG mutants produced relatively high levels of tylosin-like intermediates or shunt products. Mutants blocked in specific steps other than 3''' O-methylation, including a mutant blocked in 2''' O-methylation of demethylmacrocin, produced normal levels of macrocin O-methyltransferase. Mutants apparently containing specific tylosin structural gene mutations produced normal levels of aerial mycelia and spores, produced low levels of tylosin aldehyde reductase, and were resistant to high levels of tylosin. However, three atypical tylG mutants produced no tylosin-like compounds, could not cosynthesize tylosin with any other tyl mutant, could not bioconvert tylactone or macrocin to tylosin, and produced no macrocin O-methyltransferase. These three mutants produced elevated levels of tylosin aldehyde reductase. In addition, one was very succeptible to tylosin and did not produce aerial mycelia or spores.

New anthracycline metabolites from mutant strains of Streptomyces galilaeus MA144-M1. I. Isolation and characterization of various blocked mutants

During genetic study on obtaining high-yield variants of aclacinomycin A-producer, a variety of blocked mutants were isolated from Streptomyces galilaeus MA144-M1 and were characterized. The isolated mutants included those which accumulated only specific components of parental glycosides, those which produced new aklavinone glycosides devoid of parental rhodosamine or both rhodinose and cinerulose, those which produced non-glycosidic aglycones, and antibiotic-negative mutants, some of which were able to glycosidate exogenous aklavinone. By biotransformation with the aglycone feeding culture, the precursor activity of new aglycones was also tested. From the results and in relation to the characterization of isolated mutants, the biosynthetic pathway of aclacinomycin A and related antibiotics is discussed.

New anthracyclines, feudomycins, produced by the mutant from Streptomyces coeruleorubidus ME130-A4

Various blocked mutants were isolated from Streptomyces coeruleorubidus ME130-A4 by NTG and UV treatments. Among them, mutant strain 4N-140 produced new anthracycline feudomycins A and B having new aglycones in which the side chain at C-9 position of daunomycinone was ethyl and acetonyl, respectively. New aglycones feudomycinones C and D having methyl at C-9 and additional groups at C-10 of daunomycinone were also isolated from this strain.

Transduction in Streptomyces hygroscopicus mediated by the temperate bacteriophage SH10

The temperate actinophage SH10 mediates generalized transduction in Streptomyces hygroscopicus at low frequency. The efficiency of transduction depends on the average phage input, age of outgrowing spores of the recipient and on the selective marker. The highest EOT was found for the auxotrophic mutants 21(phe-) and 5(try-) (4.2 x 10(-6) and 2.7 x 10(-6), respectively). Transduction of the thermosensitive mutant NG14-216 ts 35 was two orders of magnitude lower (2.5 x 10(-8)). The transductant colonies segregated into stable and unstable clones. Stable transductants were never found to be lysogenic for phage SH10.

Interspecific recombination among aminoglycoside producing streptomycetes

From auxotrophic double mutants of Streptomyces rimosus forma paromomycinus and Streptomyces kanamycerticus producing little or no antibiotic, stable prototrophic recombinants were obtained with low frequencies. Most of the recombinants differed from the parents in morphology and antibiotic production. The most frequent classes of recombinants behaved as streptomycetes of the "red" series and produced a wide range of neomycin yields, in contrast to the parents which produced paromomycin and a small proportion of neomycin, or kanamycin, respectively. Hypotheses on the nature of the genetic material exchanged are discussed.

Isolation and physical characterization of streptomycete plasmids

Covalently closed circular DNA was isolated from a strain of Streptomyces coelicolor ATCC 10147 and from a strain of Streptomyces coelicolor subspecies flavus ATCC 19894, using two different methods. The two plasmids were of uniform monomer size: 8.9 kb for pS 10147, the plasmid from S. coelicolor ATCC 10147, and around 125 kb for the plasmid from S. coelicolor ATCC 19894. A restriction enzyme map was constructed for pS 10147, using seven enzymes. Four of the enzymes, (BamHI, Bgl,II, PvuII, and XhoI) cut pS 10147 once while PstI made two cuts. The GC content of this plasmid was calculated to be 72%. The possible utilisation of pS 10147 as a cloning vector in Streptomyces is discussed.

A family of r-determinants in Streptomyces spp. that specifies inducible resistance to macrolide, lincosamide, and streptogramin type B antibiotics

Inducible resistance to macrolide, lincosamide, and streptogramin type B antibiotics in Streptomyces spp. comprises a family of diverse phenotypes in which characteristic subsets of the macrolide-lincosamide-streptogramin antibiotics induce resistance mediated by mono- or dimethylation of adenine, or both, in 23S ribosomal ribonucleic acid. In these studies, diverse patterns of induction specificity in Streptomyces and associated ribosomal ribonucleic acid changes are described. In Streptomyces fradiae NRRL 2702 erythromycin induced resistance to vernamycin B, whereas in Streptomyces hygroscopicus IFO 12995, the reverse was found: vernamycin B induced resistance to erythromycin. In a Streptomyces viridochromogenes (NRRL 2860) model system studied in detail, tylosin induced resistance to erythromycin associated with N6-monomethylation of 23S ribosomal ribonucleic acid, whereas in Staphylococcus aureus, erythromycin induced resistance to tylosin mediated by N6-dimethylation of adenine. Inducible macrolide-lincosamide-streptogramin resistance was found in S. fradiae NRRL 2702 and S. hygroscopicus IFO 12995, which synthesize the macrolides tylosin and maridomycin, respectively, as well as in the lincosamide producer Streptomyces lincolnensis NRRL 2936 and the streptogramin type B producer Streptomyces diastaticus NRRL 2560. A wide range of different macrolides including chalcomycin, tylosin, and cirramycin induced resistance when tested in an appropriate system. Lincomycin was active as inducer in S. lincolnensis, the organism by which it is produced, and streptogramin type B antibiotics induced resistance in S. fradiae, S. hygroscopicus, and the streptogramin type B producer S. diastaticus. Patterns of adenine methylation found included (i) lincomycin-induced monomethylation in S. lincolnensis (and constitutive monomethylation in a mutant selected with maridomycin), (ii) concurrent equimolar levels of adenine mono- plus dimethylation in S. hygroscopicus, (iii) monomethylation in S. fradiae (and dimethylation in a mutant selected with erythromycin), and (iv) adenine dimethylation in S. diastaticus induced by ostreogrycin B.

Cloning and expression in streptomyces lividans of antibiotic resistance genes derived from Escherichia coli

Hybrid plasmids that replicate in both Escherichia coli and Streptomyces lividans were constructed in vitro by joining the E. coli-derived plasmid pACYC184 or pACYC177, at their BamHI or PstI restriction site, respectively, to S. lividans plasmid pSLP111. After introduction of the composite replicons into S. lividans by transformation, chloramphenicol (Cm) resistance encoded by pACYC184 and kanamycin resistance encoded by pACYC177 were phenotypically expressed in the S. lividans host. A Sau3A restriction endonuclease-generated deoxyribonucleic acid fragment from pACYC184 containing the entire structural gene for the Cm acetyltransferase enzyme, but lacking the nucleotide sequence ordinarily serving as the Cm resistance gene promoter, also specified resistance to Cm when introduced in either orientation into the BamHI or BclI endonuclease cleavage site of pSLP111 or into corresponding sites of the analogous plasmid pSLP101. These findings make it unlikely that the biologically active CM acetyltransferase was being made in S. lividans as part of a fused protein, but instead indicate that the ATG start codon used for initiation of translation of the Cm resistance gene in E. coli was also utilized in S. lividans. In contrast, the synthesis of messenger ribonucleic acid that encodes the Cm acetyltransferase in S. lividans was, in at least one instance, apparently initiated at nucleotide sequences within the S. lividans plasmid vector, with resulting transcriptional read-through into the E. coli-derived deoxyribonucleic acid segment.