GB1602074A - Method of facilitating genetic exchange in streptomyces and nocardia by protoplast fusion - Google Patents

Abstract

Gene exchange in organisms of the genera Streptomyces and Nocardia is facilitated by using the technique of protoplast fusion. In this technique, physical and enzymatic barriers to gene exchange are overcome and the formation of hybrid cells is favoured. The process is particularly suitable for the development of hybrid strains having specific properties.

Description

(54) METHOD OF FACILITATING GENETIC EXCHANGE IN STREP TOM YCES AND NOCARDIA BY PROTOPLAST FUSION (71) We, ELI LILY AND COMPANY, a corporation of the State of Indiana, United States of America, having a principal place of business at 307 East McCarty Street, City of Indianapolis, State of Indiana, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a new process of facilitating genetic exchange within the genera Streptomyces and Nocardia by protoplast fusion.

Genetic exchange, in conjunction with spontaneous mutation, is a natural method by which microorganisms maintain the variability needed to adapt to specific environments. Genetic exchange apparently occurs in nature, at least between members of the same species. Classical techniques used in the laboratory to effect genetic exchange between microorganisms include conjugation, DNA transformation and phage-mediated transduction. This exchange can involve either chromosomal or extrachromosomal genetic material. Genetic exchange can lead to hybrid strain formation by genetic recombination, plasmid transfer, heterokaryon formation and merodiploid formation. Finding laboratory conditions for efficient genetic exchange for microorganisms which do not possess efficient natural mating systems, however, can be very time consuming and in some cases fruitless.

Difficulties encountered in DNA transformation include physical and enzymatic barriers to DNA uptake, such as cell walls and nucleases. In phage-mediated transduction, a major difficulty encountered in developing a transducing system is isolation and identification of viruses with transducing properties for the specific microorganisms in question. The paucity of general principles and lack of a universal method to effect genetic exchange in microorganisms has hindered the development of efficient techniques for genetic exchange in many microorganisms.

Nonetheless, genetic exchange remains a very important tool to increase variability within species which produce economically and therapeutically important metabolites, such as antibiotics. Industrial applications of this tool include constructing strains which produce high levels of specific metabolites such as antibiotics, antitumor agents, enzymes and other microbial products having useful properties and constructing hybrid species which produce novel metabolites with useful properties.

A more recent method of effecting exchange of genetic material by forcing cell fusion has been used successfully in genetic studies with some eucaryotic organisms. Genetic exchange mediated by cell fusion had not been demonstrated with procaryotic microorganisms until Schaeffer et al. and Fodor and Alfodi devised a technique involving fusion of protoplasts and regeneration of cells of the genus Bacillus [P. Schaefferetal., Proc. Nat. Acad. Sci. 73,2151-2155(1976) and K.

Fodor and L. Alfoldi, Proc. Nat. Acad. Sci. 73 2147 - 2150 (1976)].

We have now discovered that it is possible to accomplish protoplast-fusioninduced genetic exchange in the procaryotic genus Streptomyces. This discovery permits the use of a general and thus extremely important technique for facilitating genetic exchange within the same or different species of the economically important genus Streptomyces. We have also discovered that it is possible to accomplish protoplast-fusion-induced genetic exchange between the genus Streptomyces and the closely related genus Nocardia.

We have discovered that it is possible to facilitate genetic exchange within the genus Streptomyces by protoplast fusion. The process of this invention involves a multistep procedure consisting of 1) protoplast formation and stabilization, 2) genetic exchange by protoplast fusion, and 3) cell regeneration from fused protoplasts. The regenerated hybrid, including recombinant, strains produced are then screened for a specifically-desired property. Examples of desired properties include production of a known metabolite, such as an antibiotic or antitumor agent, in greater yield or in a strain from which it is more easily recovered. In the case of hybrid species, desired properties can include production of new, useful metabolites or improved production of known metabolites.

This invention provides a process of facilitating genetic exchange within the genera Streptomyces and Nocardia which comprises a) forming and stabilizing protoplasts by growing cells under conditions that sensitize them to lysozyme and treating the cells with lysozyme so as to remove the cell walls, b) mixing the parental protoplasts to achieve fusion and c) regenerating cells from the fused protoplasts.

Protoplast formation and stabilization are accomplished by a) growing cells under conditions that sensitize then to lysozyme and b) treating these cells with lysozyme in a hypertonic buffer to remove cell walls and form protoplasts. Cell-wall removal may be accomplished by growing the cells for several generations in a medium containing subinhibitory concentrations of glycine. Growth in the presence of glycine renders the streptomycete cell walls susceptible to the enzyme lysozyme [M. Okanish, et al., J. Gen. Microbiol. 80, 389400 (1974)]. Although in many cases cells grown in the absence of glycine will form protoplasts, the protoplasts are formed more slowly and less efficiently.

The medium can be any suitable liquid medium, such as nutrient broth or trypticase soy broth (TSB). After growth in the presence of glycine, the cells are treated to form protoplasts. This is typically done by washing the mycelia and resuspending in a hypertonic medium. A suitable hypertonic medium contains, for example, sucrose, magnesium ions, calcium ions, and phosphate. Medium P described by Okanishi, et al., supra, is an example of a suitable hypertonic medium.

Lysozyme (1 to 2 mg/ml) is added to the cell suspension, and the resulting suspension is incubated at about 30"--37"C until protoplast formation is complete (0.5 to 2.0 hours). Completion of protoplast formation can be monitored by phasecontrast microscopy.

Protoplast fusion is achieved by mixing the protoplasts from the two parental organisms to induce the fusion of the parental protoplasts. The parental organisms may be strains of the same species (intraspecies) or different species (interspecies).

The protoplast mixture is centrifuged, and the protoplast pellet formed is resuspended in a small volume of hypertonic buffer. Fusion is enhanced by treating the parental protoplasts with polyethylene glycol (PEG). For example, a solution of PEG in hypertonic buffer (preferably a 40% solution) can be added to the resuspended protoplasts. The resulting fused protoplasts are plated on a hypertonic agar medium (e.g., medium R2 of Okanishi, et al., supra, or variations thereof).

Cell regeneration from the fused protoplasts is achieved by incubating the fused protoplasts on a hypertonic agar medium at a suitable temperature. A suitable temperature can be determined from the optimum temperatures at which the parental strains grow. To confirm genetic exchange it is preferable to use species containing suitable genetic markers such as auxotrophy or antibiotic resistance.

At this stage it is preferable, particularly in interspecies genetic crosses, to determine first the physiological growth state of the cells which is optimum for protoplast regeneration. The efficiency of protoplast regeneration can vary from < 10-5 to 5x10-', depending upon the physiological state of the cells prior to protoplast fusion. A copending UK patent application of Baltz titled Improved Method of Obtaining Streptomyces Protoplasts Capable of Cell Regeneration, Serial No. 21348/78, Serial No. 1602073, filed this even date, relates to a process of obtaining Streptomyces protoplasts which are capable of regenerating viable cells efficiently. This process involves determining the optimum state for protoplast reversion. The optimum state, the most competent state, is the transition phase between the exponential- and stationary-growth phases.

The most competent state can be determined by monitoring the Streptomyces growth cycle. This is conveniently done using a turbidometric assay and measuring change in optical density (OD) at an absorbancy of 600 nm (A600). In general, Streptomyces species undergo fairly rapid exponential growth with cell-doubling times ranging from about 1.5 hours to several hours at low cell density (A600 less than 1.5) in soluble complex media. As cell growth reaches A600 readings of 1.5 to 4.0, cells enter a transition phase which precedes the stationary growth phase. The transition phase may last from 2 to 24 hours, and cell mass may increase from 50% to 6-fold during this growth phase, depending on the species in question.

Putative hybrid, including recombinant, strains are then recloned and tested genetically by standard methods to confirm that they contain genes derived from both parents. True hybrid, including recombinant, strains are then tested for the desired beneficial property.

The process of this invention is useful for species within the genera Streptomyces and Nocardia which are normally inefficient or incapable of genetic exchange because of physical incompatibility. This method permits exchange and recombination of deoxyribonucleic acid (DNA) at very high frequencies. The method is especially useful for genetic exchange between mutant organisms of the same species, but also facilitates interspecies gene transfer. The method is particularly valuable for strain development of the antibiotic-producing Streptomyces.

For example, application of this method to Streptomycesfradiae strains readily gave recombinant yields of 104 to 105 per ml or frequencies of 10-4 to 10-3 per viable protoplast. In our laboratories previous attempts to obtain genetic recombinants of Streptomycesfradiae by standard methods [see D. A. Hopwood, Bact. Rev. 31, 373403 (1967)] were unsuccessful: recombinant clones were not detected (i.e., less than 1 in 107). Thus, the technique of our invention increases the probability of detecting a specific S. fradiae recombinational event by at least 104-fold.

Our invention is also suitable for transmission of extrachromosomal DNA (plasmids), normally non-autotransmissible, from one Streptomyces species to another. Thus, under suitable conditions plasmid-encoded genes for antibiotic synthesis or regulation can be moved from a strain with poor metabolic potential for antibiotic synthesis into a more favorable strain.

In addition, the process of our invention extends to the closely related genus Nocardia. We have found that it is possible to accomplish protoplast-fusioninduced gene transfer within the genus Nocardia and between the genus Streptomyces and the genus Nocardia.

Our invention will be especially useful for Streptomyces and Nocardia species of economic importance. Preferred Streptomyces and Nocardia species are those which produce antibiotics, such as aminoglycoside, macrolide, beta-lactam, polyether and glycopeptide antibiotics. Use of our method to effect genetic exchange when at least one parental organism is an antibiotic-producing species within the genera Streptomyces and Nocardia is, therefore, an example of an especially preferred application of our invention. For example, effecting genetic exchange when one parental organism is a microlide - antibiotic - producing, an amino - glycoside - antibiotic - producing, a beta- lactam - antibiotic producing, a polyethyl - antibiotic - producing, or a glycopeptide - antibiotic producing Streptomyces or Nocardia strain is a preferred application of our invention.

Streptomyces species which are known to produce aminoglycoside antibiotics include, for example: S. kanamyceticus (kanamycins), S. chrestomyceticus (aminosidine), S. grisoeflavus (antibiotic MA 1267), S. microsporeus (antibiotic SF767), S., ribosidificus (antibiotic SF733), S. flavopersicus (spectinomycin), S. spectabilis (actinospectacin), S. rimosus forma paromomycinus (paromomycins, catenulin), S. fradiae var. italicus (aminosidine), S. bluensis var. bluensis (bluensomycin), S. catenuale (catenulin), S. olivoreticuli var. Cellulophilus (destomycin A), S. tenebrarius (tobramycin, apramycin), S. lavendulae (neomycin), S. albogriseolus (neomycins), S. albus var. metamycinus (metamycin), S. hygroscopicus var. sagamiensis (spectinomycin), S. bikiniensis (streptomycin), S. griseus (streptomycin), S. erythrochromogenes var. narutoensis (streptomycin), S. poolensis (streptomycin), S. galbus (streptomycin), S. rameus (streptomycin), S. olivaceus (streptomycin), S. masheunsis (streptomycin), S. hygroscopicus var. limoneus (validamycins), S. rimofaciens (destomycins), S. hygroscopicus forma glebosus (glebomycin), S. fradiae (hybrimycins neomycins), S. eurocidicus (antibiotic A16316-C), S. aquacanus (N-methyl hygromycin B), S. crystallinus (hygromycin A), S. noboritoensis (hygromycin), S. hygroscopicus (hygromycins), S. atrofaciens (hygromycin), S. kasu gasp in us (kasugamycins), S. kasugaensis (kasugamycins), S. netropsis (antibiotic LL-AM31), S. lividus (lividomycins), S. hofeunsis (seldomycin complex), and S. can us (ribosyl paromamine).

Streptomyces and Nocardia species which are known to produce macrolide antibiotics include, for example: N. gardneri (proactinomycin), N. mesenterica (mesenterin), S. caelestis (antibiotic M188), S. platensis (platenomycin), S. rochei var. volubilis (antibiotic T2636), S. venezuelae (methymycins), S. griseofuscus (bundlin), S. narbonensis (josamycin, narbomycin), S. fungicidicus (antibiotic NA 181), S. grisoefaciens (antibiotic PA133A, B), S. roseocitreus (albocycline), S. bruneogriseus (albocycline), S. roseochromogenes (albocycline), S cinerochromogenes (cineromycin B), S. albus (albomycetin), S. felleus (argomycin, picromycin), S. rochei (lankacidin, borrelidin), S. violaceoniger (lankacidin), S. griseus (borrelidin), S. maizeus (ingramycin), S. albus var. coilmyceticus (coleimycin), S. mycarofaciens (acetyl-leukomycin, espinomycin), S. hygroscopicus (turimycin, relomycin, maridomycin, tylosin, carbomycin), S. griseospiralis (relomycin), S. lavendulae (aldgamycin), S. rimosus (neutramycin), S. deltae (deltamycins), S. fungicidicus var. espinomycedcus (espinomycins), S. furdicidicus (mydecamycin), S. ambofaciens (foromacidin D), S. eurocidicus (methymycin), S. griseolus (griseomycin), S. flavochromogenes (amaromycin, shincomycins), S. fimbriatus (amaromycin), S. fasciculus (amaromycin), S. erythreus (erythromycins), S. antibioticus (oleandomycin), S. olivochromogenes (oleandomycin), S. spinichromogenes var. suragaoensis (kujimycins), S. kitasatoensis (leucomycin), S. narbonensis var. josamycedeus (leucomycin A3, josamycin), S. albogriseolus (mikonomycin), S. bikiniensis (chalcomycin), S. cirratus (cirramycin), S. djakartensis (niddamycin), S. eurythermus (angolamycin), S. fradiae (tylosin, lactenocin, macrocin), S. goshikiensis (bandamycin), S. griseoflavus (acumycin), S. halstedii (carbomycin), S. tendae (carbomycin), S. macrosporeus (carbomycin), S. thermotolerans (carbomycin), andS. albireticuli (carbomycin).

Streptomyces and Nocardia species which are known to produce beta-lactam antibiotics include, for example: S. lipmanii (A16884, MM 4550, MM 13902), N. uniformis (nocardicin), S. clavuligerus (A16886B, clavulanic acid), S. lactamdurans (cephamycin C), S. griseus (cephamycin A, B), S. hygroscopicus (deacetoxycephalosporin C), S. wadayamensis (WS-3442-D), S. chartreusis (SF 1623), S. heteromorphus and S. panayensis (C2081X); S. cinnamonensis, S. fimbriatus, S. halstedii, S. rochei and S. viridochromogenes (cephamycins A, B); S. cattleya (thienamycin); and S. olivaceus, S.flavovirens, S.flavus, S. fulvo viridis, S. argenteolus, and S. sioyaensis (MM 4550 and MM 13902).

Streptomyces species which are known to produce polyether antibiotics include, for example; S. albus (A204, A28695A and B, salinomycin), S. hygroscopicus (A218, emericid, DE3936), A120A, A28695A and B, etheromycin, dianemycin), S. griseus (grisorixin), S. conglobatus (ionomycin), S. eurocidicus var. asterocidicus (laidlomycin), S. lasaliensis (lasalocid), S. ribosidificus (lonomycin), S. cacaoi var. asoensis (lysocellin), S. cinnamonensis monensin S. aureofaciens (narasin), S. gallinarius) (RP 30504), S. longwoodensis (lysocellin), S. flaveolus (CP38936), S. mutahilis (S-11743a), and S. violaceoniger (nigericin).

Streptomyces and Nocardia species which are known to produce glycopeptide antibiotics include, for example: N. fluctiferi (ristomycin), N. lurida (ristocetin), N. actinoides (aetinoidin), S. orientalis and S. haranomachiensis (vancomycin); S. canaiaus (A-3SSIZ, avoparcin), and S. eburosporeus (LL-AM 374).

Other useful antibiotic-producing steptomyces species of interest include strains of S. coelicolor, S. capreolus and S. lincolnensis.

Processes wherein genetic exchange is intraspecies suitably include those wherein the exchange is between strains of S. fradiae, S. griseofuscus S. cinnamonensis S. lipmanii S. aureofaciens S. candidus S. tenebrarius S. erythraeus S. griseus S. hygroscopicus S. clavuligerus S. bikiniensis S. coelicolor S. ambofaciens S. albogriseolus, S. albus S. aquacanus S. capreolus. S. cattleya S. crystallinus S. kanamyceticus S. kasugaensis S. kasugasp in us S. kitasatonsis S. lactamdurans S. lasaliensis S. lavendulae S. lincolnensis S. narbonensis S. noboritoensis S. orientalis or S. rimosus.

In order to illustrate more fully the operation of this invention, the following specific examples are provided: EXAMPLE 1 Streptomyces fradiae auxotrophic mutants Al (leu) and D6 (met) were used.

Liquid nitrogen suspensions of vegetative cells (0.5 ml) were inoculated separately into 50 ml of trypticase soy broth (TSB) containing 0.4% glycine and 0.4% maltose.

The cultures were incubated at 370C for 18 hours with aeration (250 RPM; 2.5-cm stroke). The mycelia were washed by centrifugation and then resuspended in 20 ml of medium P (M. Okanishi, et al., supra) containing lysozyme (I mg/ml). The suspended mycelial cells were incubated for 2 hours at 300 C. The resulting protoplasts were mixed, centrifuged, and then resuspended in 1 ml of medium P.

Solutions of PEG 6000 in medium P (0.9 ml) at various concentrations were each added to 0.1 ml of the protoplast suspension to induce cell-membrane fusion. The fused protoplasts were immediately diluted in medium P and plated on a modified R2 medium (Okanishi, et al., supra, supplemented with 20% sucrose and containing no casamino acids). The results are summarized in Table 1.

TABLE 1 Effect of PEG Concentration on Recombination Frequency Protoplasts PEG Solution Recombinants Recombination Condition Added Added per ml frequency (%)^ 0.1 ml cells + 0.9 ml60% PEG 4.3x103 2.2 2 0.1 ml cells + 0.9 ml 40% PEG 5.9x 103 3.0 3 0.1 ml cells + 0.9 ml FS* 40% PEG 1.1x104 5.6 4 0.1 ml cells + 0.9 ml FS 30% PEG 4.9x 103 2.5 5 0.1 ml cells + 0.9 ml FS 20% PEG 2.9x 103 1.5 6 Olmicells + 0.9mlFSOPEG l.9x102 0.1 no. of prototrophs/ml xlOO survivorslml *FS-filter sterlized (Millipore .45 microns) ("Millipore" is a Registered Trade Mark) The above mating was repeated using a 40% solution of filter-sterilized PEG. A recombination frequency of 3.5xl04 recombinants per ml was obtained. The recombinant colonies were recloned on nonhypertonic selective medium and tested for stability. Of the ten recombinants tested, all were prototrophic and stable (did not lose selected marker on extensive subculture under nonselective conditions).

EXAMPLE 2 Streptomycesfradiae auxotrophic mutants were used. At least one parent strain contained two auxotrophic markers and a spectinomycin resistance (spc) marker.

Each of the genetically-marked S. fradiae strains was grown in TSB containing 0.4% glycine. When growth reached an optical density of 1.5 to 5, as measured at 600 nm in a colorimeter (Bauch and Lomb), the mycelia were washed twice by centrifugation and then were resuspended in medium P (M. Okanishi, et al., supra).

Lysozyme (1 to 2 mg/ml) was added to the suspension. The suspended mycelial cells were incubated for 0.5 to 2 hours at 300 or 34"C. The resulting protoplasts were mixed (0.5 ml of each parent suspension). The mixture was washed several times by centrifugation, resuspending in medium P and finally resuspending in 0.1 ml of medium P. A solution of 40% PEG 6000 in medium P (0.9 ml) was added to the final suspension to induce cell-membrane fusion. Protoplast fusion was confirmed by phase-contrast microscopy. The fused protoplasts were immediately diluted into one of the following media: medium P containing 40% PEG, medium P, or distilled water. The dilutions were plated on medium R2 (Okanishi, et al., supra) to allow detection of recombination and regeneration of prototrophic recombinants. The R2 medium used contained asparagine instead of proline as nitrogen source.

Recombinants were counted after 10 to 24 days incubation at 340 C. In many of the crosses the prototrophic recombinants were further tested for the presence of an unselected marker (spectinomycin resistance) to eliminate single mutant reversion artifacts. Additional controls were carried out to confirm recombination. Total recombinants are based on original volumes of mixed protoplasts which generally contained from 108 to 109 protoplasts/ml, as determined by direct counting in a hemocytometer.

A summary of several genetic crosses by protoplast fusion is given in Table 2.

TABLE 2 Parental Markers # Prototrophic Spectinomycin PEG Dilution Recombinants, or Resistant Condition Parent 1 Parent 2 Treatment Medium Revertants/ml # Prototrophs 1 metA arg spc metB + P+PEG 2.4x104 6/7 2 metA arg spc metB - P 6.6x10 8/8 3 metA arg spc metB - H2O 7.0x10 11/11 4 metA arg spc - + P+PEG < 10 0/0 5 metA arg spc - - P < 10 0/0 6 metA arg spc - - H2O < 10 0/0 7 - metB + P+PEG 2x10 0/3 8 - metB - P 2x10 0/6 9 - metB - H2O 2x10 0/8 10 metA arg spc cysD + P 1.1x105 ND* 11 - cysD + P < 10 ND 12 metA arg spc - + P < 10 ND *Not determined.

#Determined on R2 medium.

#Marker designations are those of Hopwood, et al. [Bact. Rev. 37, 371-405 (1973)]. The metA, arg and metB markers are auxotrophic. The spc marker designates resistance to 50 g/ml spectinomycin.

As was the case in Example I, a lower. but significant, level of recombination was obtained by centrifuging the protoplasts and resuspending in medium P without PEG. This level of protoplast fusion is presumably due to the presence of Ca+" in the buffer. Dilution of the protoplasts in distilled water reduced the number of recombinants by 100-fold. Virtually all of the genetic recombinants tested contained the spc marker from the strain carrying the metA arg markers, ruling out the possibility that reversion of the metB strain might account for the data. The doubly marked auxotrophic strain has never been shown to revert to prototropy, thus eliminating reversion of this strain as an explanation of the results.

The other controls in Table 2 give additional evidence that recombination does indeed take place after protoplast fusion. Upon recloning, all putative recombinants were shown to be stable. The S. fradiae strain used is one which produces the antibiotic tylosin. Many genetic recombinants of this S. fradiae were shown to be tylosin producers.

EXAMPLE 3 Streptomyces griseofuscus was used in these genetic crosses. The procedures were the same as those used in Example 2 except that: 1) the TSB was supplemented with 0.8% glycine and 2) recombinant colonies were counted after 7 days incubation at 340C. Results are summarized in Table 3. In all six conditions protoplasts were treated with PEG, diluted in medium P and plated on medium R2.

In all cases, the frequency of genetic recombinants was from 103 to 104-fold higher than background prototrophic revertants.

TABLE 3 Parental Markers Prototrophic Recombinants or Condition Parent 1 Parent 2 Revertants/ml 1 met arg 3.1x104 2 met trp 4.8x103 3 arg trp 4.2x104 4 met < 101 5 arg 1.0x10' 6 trp < 101 EXAMPLE 4 Streptomyces fradiae (met) and Streptomyces bikiniensis (nic ade) were used Each culture was incubated according to the procedure described in Example 1.

Crosses made between the strains are listed in Table 4 where conventional mating techniques are compared to the protoplast fusion technique. Table 4 demonstrates that protoplast fusion gives at least a 200-fold increase in recombination frequency compared to conventional mating procedures.

TABLE 4 Comparison of Recombination Frequencies from an Interspecies Cross Employing Vegetative Cells to Interspecies Cross Mediated by Protoplast Fusion.

1. Vegetative Cells A. Recombination Frequency Selected Markers Suspension nic ade met S. bikiniesis x S. fradiae 1.1x10-8 < 1x10-9 S. bikiniensis < 5.9x10-9 < 5.9x10-9 S. fradiae - < 2.4x 10-8 B. Recombinant Analysis Stability of Unselected Markers Selected Recombinant No. Marker nic ade Colony Morphology3 +2 - Sb 2 + - Sb 3 + - Sb 2. Protoplast Fusion4 A. Recombination Frequency Selected Markers Suspension PEG nic ade met S. bikiniensis x S.fradiae + 2.5x10-6 1.7x10-5 S. bikiniensis x S.fradiae - < 4.4x10-7 < 4.4x10-7 S. bikiniensis - - < 3.3x10-8 < 3.3x10.8 S. fradiae - - - - < 4.4x10-7 B. Recombinant Analysis Unselected Markers Stability of Recombinant Selected Selected Colony No. Marker Marker nic ade Morphology35 1 ade + - Sb 2 ade + - Sb 3 ade + - Sb 4 ade + - Sb 5 ade + - Sb 6 ade - - Sb 7 ade + - Sb 8 ade + Sb 9 nic + + Sb 10 nic + + Sb 1Medium and mating conditions according to Hopwood and Sermonti, Adv.

Genet, 11, 273-342 (1962).

2After recloning on the selective media, recombinants were grown for 48 hrs in TSB, sonicated and plated on TSB agar. After 4 days incubation, 10 colonies from each recombinant were retested for the selected marker. The sign + means all were positive; the sign - means some of the colonies lost the selected marker.

3Sb=S. bikiniensis morphology 4Protoplast fusion induced by 40% PEG in medium P (filter-sterilized) 5All Sb colonies produced zorbamycin EXAMPLE 5 Several interspecies crosses were studied using the protoplast-fusion technique. Strains were incubated overnight under optimal cultural conditions with growth-limiting concentrations of glycine. Protoplasts were isolated from each strain by treatment with lysozyme (1 mg/ml) at 300C for 1 to 4 hours. The resulting protoplasts were mixed and resuspended in medium P (see Example 1). A solution of 40% PEG 6000 in medium P (0.9 ml) was added to the final suspension to induce cell-membrane fusion. As a control, 0.1 ml of the protoplast suspension was resuspended in 0.9 ml of medium P. The treated and nontreated protoplasts were immediately diluted in medium P and plated on selective medium (R2 without casamino acid supplementation). The following strains were used: Organism Phenotype3 Streptomyces coelicolor 1190 his ura cap Nocardia erythropolis No 17 Streptomyces fradiae D6 met Streptomyces cinnamonensis 3823-A5 leu Streptomyces lipmanii A 16884 Streptomyces tenebrarius St26-A4 his Streptomyces lipmanii LA423 lys Streptomyces clavuligerus J1 UD Streptomyces cinnamonensis M2 UD Streptomyces aureofaciens S5 UD Streptomyces aureofaciens S15 UD Streptomyces candidus A35512-a1 anthranilic acid Streptomyces bikiniensis 214-44 nic ade Streptomyces fradiae SFA2 cys S. lipmanii protoplasts do not regenerate on R2 cap represents resistance to chloramphenicol at 20 g/ml; the remaining markers are auxotrophic 3UD=unidentified auxotrophic requirement TABLE 5 Selective Number of Cross PEG1 Media 2.3A Prototrophs per ml S. coelicolor 1190xN.

Claims (61)

WHAT WE CLAIM IS:-

1. A process for facilitating genetic exchange within the genera Streptomyces and Nocardia which comprises A) forming and stabilizing protoplasts by growing cells under conditions that sensitize them to lysozyme and treating the cells with lysozyme so as to remove the cell walls, B) mixing the parental protoplasts to achieve fusion and C) regenerating cells from the fused protoplasts.

2. The process of claim 1 wherein protoplasts are formed during the transitional growth phase.

3. The process of claims 1 or 2 wherein protoplasts are formed by growing cells on a hypertonic nutrient medium in the presence of a non-inhibiting concentration of glycine, adding lysozyme and incubating the resulting suspension at 30 to 370C.

4. The process of any of claims 1 to 3 which comprises enhancing protoplast fusion by treating the protoplasts with polyethylene glycol.

5. The process of any of claims I to 4 wherein the genetic exchange facilitated is intraspecies.

6. The process of any of claims 1 to 4 wherein the genetic exchange facilitated is interspecies.

7. The process of any of claims 1 to 6 wherein the genetic exchange is within the genus Streptomyces.

8. The process of any of claims 1 to 6 wherein the genetic exchange is within the genus Nocardia.

9. The process of any of claims 1 to 6 wherein one parental organism is an antibiotic-producing species within the genera Streptomyces and Nocardia.

10. The process of claim 9 wherein the genetic exchange is within the genus Streptomyces.

11. The process of claim 9 wherein the genetic exchange is within the genus No cardia.

12. The process of any of claims 1 to 6 wherein one parental organism is an aminoglycoside - antibiotic - producing species.

13. The process of claim 12 wherein one parental organism is selected from S. kanamyceticus, S. chrestomyceticus, S. griseoflavus, S. microsporeus, S. ribosidificus. S. flavoperisicus, S. spectabilis, S. rimosus forma paromomycinus, S. fradiae var. italicus, S. bluensis var. bluensis. S. catenulae, S. olivoreticuli var. cellulophilus. S. tenebrarius.

S. lavendulae, S. albogriseolus, S. albus var. metamycinus, S. hygroscopicus var. sagamiensis, S. bikiniensis, S. griseus, S. erythrochromogenes var. narutoensis, S. poolensis, S. galbus, S. rameus, S. olivaceus, S. mashuensis, S. hygroscopicus var. limoneus, S. rimofaciens, S. hygroscopicus forma glebosus, S. fradiae, S. eurocidicus, S. aquacanus, S. crystallinus, S. noboritoensis, S. hygroscopicus, S. atrofaciens. S. kasugaspinus, S. kasugaensis, S. netropsis, S. lividus, S. hofuensis, and S. can us.

14. The process of any of claims 1 to 6 wherein one parental organism is a macrolide - antibiotic - producing species.

15. The process of claim 14 wherein one parental organism is selected from S. caelestis, S. platensis, S. rochei var. volubilis, S. venezuelae, S. griseofuscus. S. narbonensis, S. fungicidicus, S. griseofaciens, S. roseocitreus, S. bruneogriseus, S. roseochromogenes, S. cinerochromogenes, S. albus, S. felleus, S. rochei, S. violaceoniger, S. griseus, S. maizeus, S. albus var. coilmyceticus, S. mycarofaciens, S. hygroscopicus, S. griseospiralis, S. lavendulae, S. rimosus, S. deltae, S. fungicidicus var. espinomyceticus, S. furdicidicus, S. ambofaciens, S. eurocidicus, S. griseolus, S. flavochromogenes, S. fimbriatus, S. fasciculus, S. erythreus, S. antibioticus, S. olivochromogenes, S. spinichromogenes var. suragaoensis, S. kitasatoensis, S. narbonensis var. josamyceticus, S. albogriseolus, S. bikiniensis, S. cirratus, S. djakartensis, S. eurythermus, S. fradiae, S. goshikiensis, S. griseoflavus, S. halstedii, S. tendae, S. macrosporeus, S. thermotolerans, N. gardneri, N. mesenterica and S. albireticuli.

16. The process of any of claims 1 to 6 wherein one parental organism is a beta - lactam - antibiotic - producing species.

17. The process of claim 16 wherein one parental organism is selected from S. lipmanii. S. clavuligerus, S. lactamdurans, S. griseus, S. hygroscopicus, S. wadayamensis, S. chartreusis, S. heteromorphus, S. panayensis, S. cinnamonensis, S. fimbriatus. S. halstedii, S. rochei, S. viridochromogenes, S. cattleya, S. olivaceus, S. flavovirens, S. flavus, S. fulvoviridis, S. argenteolus, N. uniformis and S. sioyaensis.

18. The process of any of claims 1 to 6 wherein one parental organism is a polyether - antibiotic - producing species.

19. The process of claim 18 wherein one parental organism is selected from S. albus, S. hygroscopicus. S. griseus, S. conglobatus. S. eurocidicus var. asterocidicus, S. lasaliensis, S. ribosidificus. S. cacaoi var. asoensis, S. cinnamonensis, S. aureofaciens, S. gallinarius, S. longwoodensis, S. flaveolus, S. mutabilis, and S. violaceoniger.

20. The process of any of claims 1 to 6 wherein one parental organism is a glycopeptide - antibiotic - producing species.

21. The process of claim 20 wherein one parental organism is selected from S. orientalis, S. haranomachiensis, S. candidus, N.fructifeui, N. lurida, N. actinoides, and S. eburosporeus.

22. The process of claim 5 wherein the genetic exchange is between S. fradiae strains.

23. The process of claim 5 wherein the genetic exchange is between S. griseofuscus strains.

24. The process of claim 5 wherein the genetic exchange is between S. cinnamonensis strains.

25. The process of claim 5 wherein the genetic exchange is between S. lipmanii strains.

26. The process of claim 5 wherein the genetic exchange is between S. aureofaciens strains.

27. The process of claim 5 wherein the genetic exchange is between S. candicus strains.

28. The process of claim 5 wherein the genetic exchange is between S. tenebrarius strains.

29. The process of claim 5 wherein the genetic exchange is between S. arythraeus strains.

30. The process of claim 5 wherein the genetic exchange is between S. griseus strains.

31. The process of claim 5 wherein the genetic exchange is between S. hygroscopicus strains.

32. The process of claim 5 wherein the genetic exchange is between S. clavuligerus strains.

33. The process of claim 5 wherein the genetic exchange is between S. bikiniensis strains.

34. The process of claim 5 wherein the genetic exchange is between S. coelicolor strains.

35. The process of claim 5 wherein the genetic exchange is between S. ambofaciens strains.

36. The process of claim 5 wherein the genetic exchange is between S. albogriseolus strains.

37. The process of claim 5 wherein the genetic exchange is between S. albus strains.

38. The process of claim 5 wherein the genetic exchange is between S. aquacanus strains.

39. The process of claim 5 wherein the genetic exchange is between S. capreolus strains.

40. The process of claim 5 wherein the genetic exchange is between S. cattleya strains.

41. The process of claim 5 wherein the genetic exchange is between S. crystallinus strains.

42. The process of claim 5 wherein the genetic exchange is between S. kanamyceticus strains.

43. The process of claim 5 wherein the genetic exchange is between S. kasugaensis strains.

44. The process of claim 5 wherein the genetic exchange is between S. kasugaspinus strains.

45. The process of claim 5 wherein the genetic exchange is between S. kitasatoensis strains.

46. The process of claim 5 wherein the genetic exchange is between S. lactamdurans strains.

47. The process of claim 5 wherein the genetic exchange is between S. lasaliensis strains.

48. The process of claim 5 wherein the genetic exchange is between S. lavendulae strains.

49. The process of claim 5 wherein the genetic exchange is between S. lincolnensis strains.

50. The process of claim 5 wherein the genetic exchange is between S. narbonensis strains.

51. The process of claim 5 wherein the genetic exchange is between S. noboritoensis strains.

52. The process of claim 5 wherein the genetic exchange is between S. orientalis strains.

53. The process of claim 5 wherein the genetic exchange is between S. rimosus strains.

54. The process of claim 6 wherein the genetic exchange is between S. fradiae and S. bikiniensis.

55. The process of claim 6 wherein the genetic exchange is between S. fradiae and S. cinnamonensis.

56. The process of claim 6 wherein the genetic exchange is between S. lipmanii and S. tenebrarius.

57. The process of claim 6 wherein the genetic exchange is between S. cinnamonensis and S. aureofaciens.

58. The process of claim 6 wherein the genetic exchange is between S. aureofaciens and S. candidus.

59. The process of claim 6 wherein the genetic exchange is between S. lipmanii and S. clavuligerus.

60. The process of claim 6 wherein the genetic exchange is between N. erythropolis and S. coelicolor.

61. A process for facilitating genetic exchange within the genera Streptomyces and Nocardia according to claim 1 substantially as hereinbefore described with particular reference to any of Examples 1 to 5.