Improvement of the productivity of elasnin, a specific elastase inhibitor, by Streptomyces noboritoensis KM-2753

Streptomyces noboritoensis KM-2753, an elasnin-producing strain, co-produces an antimycin complex and its elasnin productivity is low (0.006 mg/ml). To obtain mutants possessing higher degrees of elasnin productivity and deficient in antimycin production, the strain was treated with N-methyl-N'-nitro-N-nitrosoguanidine (NTG), ultraviolet light, acriflavine (AF) and high temperature. Mutant N-134 obtained by treatment with NTG was 108 times higher than the original strain in elasnin productivity and produced no antimycin. Strain AF-17 obtained by AF treatment and strain H-80 obtained by incubation at high temperature showed 715 and 428 times higher productivities than that of the original strain, respectively. The productivity of elasnin was further increased 1.6 approximately 2.6 times by addition of saturated fatty acids, especially lauric acid, to the culture. Consequently, strain AF-17 produced 11.1 mg/ml of elasnin in the presence of 10 microgram/ml of lauric acid.

Isolation of viable deletion mutants of Streptomyces actinophage (Pal 6) and their molecular characterization

Deletion mutants of bacteriophage Pal 6 were isolated by successive treatments of either heat (60 degrees C) or pyrophosphate (10 mM). These mutants were characterized by restriction enzyme cleavage analysis. The pyrophosphate resistant clones lost the whole Eco R1 fragment in which the Sal I site is located, as well as an unrelated Hind III fragment. These results show that the region containing the Sal I site in the phage genome is not essential for phage viability. This single Sal I site is therefore suitable as a potential insertion site for DNA cloning. On the other hand, the heat resistant clones that were isolated and characterized do not appear to have detectable deletions as indicated by their Eco R1 DNA digestion pattern.

Mutagenicity of halogenated aliphatic hydrocarbons in Salmonella typhimurium, Streptomyces coelicolor and Aspergillus nidulans

Eight structurally related halogenated aliphatic hydrocarbons mono-, di- and trichloroacetaldehyde (the last in the anhydrous and hydrate form), moni-, di- and trichloroethanol and allyl chloride, were tested for their ability to induce gene mutations in prokaryotic and eukaryotic microorganisms. The genetic systems employed were the Salmonella reversion test with strain TA1535 and TA100, with and without metabolic activation, a forward and a back-mutation system in S. coelicolor and two forward mutation systems in A. nidulans. Each compound was tested with the spot and plate incorporation assay techniques. Mono-, di- and trichloroacetaldehyde were mutagenic in all the microorganisms employed; all the halogenated ethanols were positive in A. nidulans, while in S. typhimurium and in S. coelicolor the only active forms were respectively the mono- and dichloroderivatives. Allyl chloride was active in S. typhimurium and S. coelicolor and negative in A. nidulans. The technical approach as well as the complex influence of different factors (toxicity, volatility and stability) on the genetic response of each of the compounds under test did not allow to obtain more than a qualitative relationship between mutagenic potency and chemical structure.

Multiple effects induced by unstable mutation in Streptomyces lavendulae

Arg mutants, isolated from Streptomyces lavendulae at unusually high frequencies, showed several phenotypic characteristics. The characteristics common to all arg mutants include: (1) repression of beta-lactamase production, (2) inhibition of aerial mycelium formation, (3) development of acid pH, (4) low saturation density of growth in liquid culture, (5) a decrease in antibiotic production, (6) an increase in sensitivity to benzylpenicillin and (7) a decrease in production of pigment. These results suggest that the arg mutation concomitantly caused the depression of secondary metabolism in S. lavendulae.

Polyethylene glycol-assisted transfection of Streptomyces protoplasts

In the presence of polyethylene glycol (concentration optimum 20%), protoplasts of appropriate Streptomyces strains could be transfected by deoxyribonucleic acid (DNA) of five temperate phages (phi C31, VP5, R4, phi 448, and S14) belonging to four different immunity groups. Quantitation of transfection was made possible by plating the transfection mixture with excess uninfected protoplasts in soft agar overlays on protoplast regeneration medium so that plaques were easily detected. Optimum frequencies of transfection in the ranges of 10(-6)/DNA molecule and 10(-5)/viable protoplast were invariably obtained. It appeared that single DNA molecules initiated transfection events, and that the conformation of the DNA (i.e., circular or linear) was not important. Inhibition of transfection by ethylenediaminetetraacetic acid suggested that divalent cations were also observed. A minor subpopulation of protoplasts appeared to be particularly sensitive to transfection (i.e., "competent") in some DNA-host combinations. In such cases the size of this subpopulation was the major limiting factor in obtaining high transfection frequencies. The same protoplast

Unstable mutation of beta-lactamase production in Streptomyces lavendulae

Streptomyces lavendulae S55-B1 gave two distinct variants at an unusual high frequency: one is a beta-lactamase-nonproducing variant and the other is an Arg- variant. All of the Arg- variants concomitantly had no, or only very low, beta-lactamase activity and were unable to form aerial mycelia or spores. There was no significant linkage between the beta-lactamase activity and the other nutritional requirement which was analyzed. Two of the Arg- variants spontaneously gave Arg+ revertants at a very low frequency. The revertants, however, did not recover the beta-lactamase activity. It is suggested that the beta-lactamase gene may be capable of transposition with inactivation of the arg gene occurring frequently by insertion of the transposed element. Covalently closed circular deoxyribonucleic acid from S55-B1 was not detected by either cesium chloride-ethidium bromide buoyant density centrifugation or agarose gel electrophoresis.

Streptomyces albus G mutants defective in the SalGI restriction-modification system

Streptomyces albus G mutants (at least 12 of which were independent) defective in SalGI-mediated restriction (R-) were isolated after mutagenesis. Some of them lacked detectable SalGI activity in cell-free extracts. Some were also partially or completely defective in SalFI-associated modification (M-). Loss of restriction rendered S. albus G sensitive to many phages to which it was normally totally resistant. DNA from one such phage had many SalGI target sites (mean, one site per 1.35 kilobases). A mutant was isolated which was heat-sensitive for growth, apparently because it was restriction-proficient but temperature-sensitive for modification. At a rather high frequency, this mutant generated spontaneous heat-tolerant derivatives which were nearly all R-. Such R- mutants were always M- rather than being temperature-sensitive for modification. In a limited genetic analysis, the determinants of restriction and modification did not recombine with each other, and since there was no reassortment of these phenotypes among the parental output of crosses it appeared that the determinants were located close together on the chromosome.

A jumping gene in streptomyces coelicolor A3(2)

The difficulty in mapping the gene for chloramphenicol resistance (cmlR) in Streptomyces coelicolor A3(2) stock strains is possibly due to its location on different sites of the chromosome in various mixed subclones. Fresh isolates from CmlR strains show single unequivocal locations of cmlR. The same holds for CmlR strains derived as revertants from CmlS variants. The two best established sites for cmlR are one between cysA and metA, the other at right of argA, possibly in the right empty arc of the map (Fig. 2). The cmlR gene was assumed to be on a transposon (SCTn1), together with a gene for arginine-succinate synthase (argG), a gene for chromosome transfer (tra) and a gene for aereal mycelium formation (amy). In a CmlR revertant, the cmlR gene appears disjoined from argG (Fig. 5), thus showing the ability of SCTnl to be split and partially transposed. The possible wide occurrence of transposons in the genus Streptomyces is discussed.

Transfection of protoplasts from Streptomyces lividans 66 with actinophage SH10 DNA

The slightly modified procedure for the transformation of protoplasts of S. coelicolor A3 (2) with SCP2 plasmid DNA and polyethylenglycol (PEG) (Bibb et al., 1978) was extended to infection of protoplasts of S. lividans 66 with actinophage SH10 DNA (Klaus et al., 1979). Maximal yield of transfected protoplasts was obtained at 20% PEG, 3 MM sodium-citrate and 150 mM NaCl final concentrations. The efficiency of transfection was determined to be about 2 x 10(-8) to 2 x 10(-7). The average value of competent protoplasts was about 1-2 x 10(-4) of regenerating protoplasts. In comparison with outgrowing spores infected with phage particles the average burst size of transfected protoplasts was reduced from 100 to 10 pfu/infected cell, the latent period prolonged from 45 min to 120 min and the rise period was not affected.

[A new selection method for obtaining mutants of Streptomyces glaucoachromogenes producing lambdamycin using the thermophilic phage-host system Tal/Thermoactinomyces vulgaris]

In order to obtain high-producing mutants of the lambdamycin producer Streptomyces glaucoachromogenes IMET 31 118, a new selection technique using the thermophilic phage-host system Tal/Thermoactinomyces vulgaris, was developed. Lambdamycin is a yellow-green pigment antibiotic of the chromoglycoside type with antimicrobial, antiviral, cancerostatic, and ergotropic activity in vitro and in vivo. The physicochemical properties of lambdamycin resemble those of chartreusin. By means of the selection technique developed the determination of the concentration-dependent influence of lambdamycin on bacterial growth inhibition and Tal-phage development in the agar diffusion sphere of mutagen-treated colonies is possible without time and material-consuming pre-tests. A positive correlation exists between the biosynthetic capacity of mutants on solid media and in fermentation liquors. Using this new selection technique, the titres of lambdamycin in fermentation liquors of mutants could be increased by 10 to 20 fold in comparison to the wild type strain.

Aminoglycosides, genes and regulation

A major role has been played by aminoglycoside research in the development of fermentation science especially involving genetics and regulation. The first report of the use of an antibiotic to select high producers of that antibiotic was done with the streptomycin producer. Mutational biosynthesis of new antibiotics originated with studies on the neomycin producer. The first demonstration of the presence of genes coding for antibiotic inactivation in antibiotic producers was made with Streptomyces griseus, the producer of streptomycin. Induction of an enzyme involved in secondary metabolism was found first with mannosidostreptomycinase. The first example of a nonprecursor molecule which could induce an entire antibiotic biosynthetic pathway was A-Factor involved in streptomycin production. Glucose repression and amino acid repression of mannosidostreptomycinase were the first examples of carbon catabolite repression and nitrogen metabolite repression respectively of an enzyme involved in secondary metabolism. Data supporting the occurrence of nitrogen metabolite regulation of antibiotic biosynthesis were first gathered in the early days of development of the streptomycin fermentation when it was found that the slowly used soybean meal and proline were the best nitrogen sources for antibiotic production. Aminoglycoside research also provided the first explanation of a mechanism of phosphate control of antibiotic biosynthesis. The first indication that antibiotic formation is not obligatory for spore formation was provided by data on streptomycin production.

Fertility properties and regulation of antimicrobial substance production by plasmid SCP2 of Streptomyces coelicolor

Streptomyces coelicolor A3(2) possesses two plasmids (SCP1 and SCP2) that act as sex factors. The plasmid deoxyribonucleic acid isolated from S. coelicolor A3(2) SCP1- strains A617 and A585 had the same molecular weight and endonuclease cleavage pattern as the SCP2 plasmid. The plasmidless strain S18 SCP2- was isolated from the A617 X A585 cross. SCP2 plasmid-containing strains acted as donors of chromosomal markers, whereas the plasmidless strain acted as recipient. The transfer of SCP2+ donor strain markers into the SCP2- recipient occurred at high frequencies (approximately 75%), was unidirectional, was initiated from a fixed region of the chromosome, and had the SCP2 fertility factor transferred first. The introduction of the SCP2 plasmid into a recipient strain greatly reduced the recombination frequency. These fertility properties differed from those previously reported, thereby suggesting that the SCP2 plasmid examined in this investigation may be an additional variant to those described in the literature. The SCP2 plasmid also regulated production of three antibacterial substances and conveyed resistance for S. coelicolor A3(2) strains against growth inhibition by one of them.

Herbicidins F and G, two new nucleoside antibiotics

A mutant of Streptomyces saganonensis No. 4075, obtained with N-methyl-N'-nitro-N-nitrosoguanidine treatment, produced herbicidins F and G without herbicidins A and B. Isolation of the antibiotics was performed by adsorption on resinous adsorbent followed by elution with aqueous MeOH. Herbicidin F was obtained as colorless needles after extraction of the eluate using methylene dichloride. Purification of herbicidin G was completed with silica-gel chromatography to give a crystalline powder. physico-chemical characterization revealed that herbicidins F and G were new nucleoside antibiotics having an adenine moiety in their structures. There was no inhibition activity at 100 micrograms/ml of herbicidins F and G against all of bacteria and yeast tested. Herbicidin F, as well as herbicidin G, are inhibitory activity against some of fungi such as Tricophyton rubrum (MIC; 6.25 micrograms/ml), T. asteroides (6.25 micrograms/ml), T. mentagrophytes (6.25 approximately 12.5 micrograms/ml), Botrytis cinerea (12.5 micrograms/ml), Blastomyces brasiliensis (12.5 approximately 25 micrograms/ml).

Genetics of actinorhodin biosynthesis by Streptomyces coelicolor A3(2)

A series of 76 mutants of Streptomyces coelicolor A3(2) specifically blocked in the synthesis of the binaphthoquinone antibiotic actinorhodin were classified into seven phenotypic classes on the basis of antibiotic activity, accumulation of pigmented precursors or shunt products of actinorhodin biosynthesis, and cosynthesis of actinorhodin in pairwise combinations of mutants. The polarity of cosynthetic reactions, and other phenotypic properties, allowed six of the mutant classes to be arranged in the most probable linear sequence of biosynthetic blocks. One member of each mutant class was mapped unambigiguously to the chromosomal linkage map in the short segment between the hisD and guaA loci, suggesting that structural genes for actinorhodin biosynthesis may form an uninterrupted cluster of chromosomal genes.

Growth and production of anthracyclines in wild-type and mutant strains of Streptomyces galilaeus

The course of growth curves with respect to the biosynthesis of anthracyclines was followed in the wild low-producing strain Streptomyces galilaeus JA 3043 and in its mutants G-167 (producing increased quantities of glycosides of epsilon-pyrromycinone) and J-14 (accumulating free epsilon-pyrromycinone). A two-phase type of fermentation (growth phase, production phase) was observed in strains JA 3043 and J-14. The maximum production of anthracyclines occurred only after the end of intense growth of the culture. Two phases of rapid growth separated by a phase of stagnation were observed in strain G-167. The second growth phase proceeded only during late hours of cultivation and was (as compared with the first phase) associated with an intensive biosynthesis of anthracyclines.

Nitrosoguanidine-induced mutations in Streptomyces indicus

The mutagenic activities of five 1-alkyl derivatives of 3-nitro-1-nitrosoguanidine, viz. methyl, ethyl, propyl, isopentyl and octyl, were tested on Streptomyces indicus. All the compounds were found to be mutagenic. The methyl and ethyl derivatives were most effective regarding mutational frequency. The effectiveness decreased with increasing number of C-atoms in the alkyl group of the mutagens. The compounds tested had a much higher mutagenic efficiency that UV-rays. A marked variation existed in antibiotic activity among the biochemical mutants: increase, decrease or complete absence of such activity were seen.

Effect of aeration efficiency and carbon source on the production of anthracyclines in Streptomyces galilaeus

Biosynthesis of anthracyclines in Streptomyces galilaeus during submerged cultivation is considerably influenced by aeration and by the concentration of glucose in the medium. At higher values of oxygen absorption rate both the production of epsilon-pyrromycinone glycosides in the wild strain JA 3043 and its production mutant G-167 and accumulation of free epsilon-pyrromycinone in the blocked mutant G-162 were found to be higher; the production of 7-deoxyaglycones was lower in all strains. The studied strains differed in the rate of glucose consumption and in the ability to utilize starch for the biosynthesis of anthracyclines. A two-fold concentration of glucose in the medium resulted in the G-162 strain in an increase of the yield of epsilon-pyrromycinone by 120%. The production of glycosides in strain G-167 increased even after exhaustion of glucose from the medium and the amount of 7-deoxyaglycones simultaneously decreased.

Method for the rapid screening of cellulolytic streptomycetes and their mutants

A method for the rapid screening of cellulolytic streptomycetes and their mutants is reported. The technique consists of a plate assay on media containing filter paper fibres as cellulose substrate. The cellulolytic activity is detected and measured by the formation of clearing zones around the streptomycete colonies. The sensitivity of the method is increased considerably by subjecting the plates to an additional incubation period at 43 degrees C in the presence of a buffer at pH 5.3. by replicating these colonies on other Petri plates containing the appropriate media, it is possible to assess rapidly, not only the degree of catabolic repression of the cellulase production by glucose, but also, in a semiquantitative way, the amount of enzymes produced.

Genetics and biochemical studies of chloramphenicol-nonproducing mutants of Streptomyces venezuelae carrying plasmid

Chloramphenicol-nonproducing and plasmid-less mutants obtained previously by treatment with acriflavine still produced a small amount of chloramphenicol in a medium. To study the role of plasmid in chloramphenicol production, 70 chloramphenicol-nonproducing mutants were isolated by acriflavine treatment, high-temperature incubation, UV-irradiation or nitrosoguanidine treatment, starting from a producer (SVM2). Most of them did not produce any amount of chloramphenicol. One mutant, SVM2-2A7 was found to produce 1-deoxychloramphenicol instead of chloramphenicol. The mutations (cpp) affecting chloramphenicol production were analyzed by crosses with a producing strain carrying the complementing auxotrophic markers. Except for the plasmid-less strains, all Cpp mutations including the 1-deoxychloramphenicol-producing mutation were mapped between met and ilv on the chromosome. Additional crosses indicated that these chromosomal cpp mutants still carried the plasmids which had a role in increasing chloramphenicol production. Therefore, it can be concluded that the structural genes for all or most steps of chloramphenicol biosynthesis including the 3-hydroxylation of p-aminophenylalanine are located between met and ilv on the chromosome of S. venezuelae and that the plasmid plays an important role in increasing the chloramphenicol production. The activity of arylamine synthetase involved in the initial step of the chloramphenicol biosynthesis was unrelated to the presence or absence of plasmid. Moreover, the presence of plasmids was not required for host resistance to chloramphenicol.

Phenoxazinone biosynthesis: accumulation of a precursor, 4-methyl-3-hydroxyanthranilic acid, by mutants of Streptomyces parvulus

Mutants of Streptomyces parvulus that are blocked in the synthesis of the phenoxazinone-containing antibiotic, actinomycin, were isolated by the 'agar piece' method (after ultraviolet irradiation or treatment with 8-methoxypsoralen plus near-ultraviolet light). Radiolabelling experiments in conjunction with paper, thin-layer and column chromatography revealed that 4-methyl-3-hydroxyanthranilic acid (MHA) is a major metabolite accumulated by these mutants. Studies in vitro and in vivo provided evidence that MHA is a precursor of the phenoxazinone chromophore, actinocin. Normally MHA does not accumulate during growth or antibiotic synthesis by the parental strains. Protoplasts derived from the mutant strain AM5 synthesized MHA in significant amounts. A scheme is proposed for the biosynthesis of actinomycin D that accounts for the accumulation of MHA by the mutants.

Factors affecting recombinant frequency in protoplast fusions of Streptomyces coelicolor

The optimum concentration of polyethylene glycol 1000 (PEG) for the production of recombinants through protoplast fusion in Streptomyces coelicolor was about 50% (w/v). The addition of 14% (v/v) dimethyl sulphoxide to the fusion mixture enhanced recombination frequencies, but only at sub-optimal PEG concentrations. After treatment of protoplasts with 50% PEG for 1 min, the frequency of recombinants in a multi-factor 'cross' sometimes exceeded 20% of the total progeny. The frequency of recombinants in the progeny could be significantly enhanced by ultraviolet irradiation of the parental protoplast suspensions immediately before fusion.

Simultaneous loss of multiple differentiated functions in aerial mycelium-negative isolates of streptomycetes

Germination and outgrowth of spores of Streptomyces alboniger, Streptomyces scabies, and Streptomyces violaceus-ruber in the presence of intercalating dyes resulted in a high frequency (2 to 20%) of occurrence of aerial mycelium-negative (Amy-) isolates. Coincident with the appearance of the Amy- trait was the loss of several differentiated functions, including the characteristic pigments and earthy odor of the wild types. All S. alboniger, 27% of S. scabies, and 39% of the S. violaceus-ruber Amy- isolates were arginine auxotrophs. The missing enzyme step was identified as argininosuccinate synthetase by using a sensitive microassay for estimation of enzyme activity. The remainder of the S. scabies and S. violaceus-ruber isolates were prototrophs. In addition, S. alboniger Amy- isolates failed to produce or respond to the stimulator of aerial mycelium formation isolated from the wild type. The Amy- isolates did not revert to either Amy+ of Arg+. The lack of any detectable reversion, coupled with the high frequency of curing, supports the idea that a deletion of genetic material, possibly a plasmid, has occurred.

A new site-specific endonuclease from Streptomyces lavendulae (SlaI)

A new restriction-like endonuclease, SlaI, was found and partially purified from Streptomyces lavendulae ATCC8664. This endonuclease cleaved bacteriophage lambda DNA at only one site, and cytosine-substituted bacteriophage T4 DNA at 16 sites. The recognition sequence was determined by using SlaI fragments of cytosine-substituted bacteriophage T4 DNA. The hexanucleotide recognized by SlaI endonuclease was (Formula: see text), with the sites of cleavage as indicated by the arrows. Therefore, SlaI endonuclease was an isoschizomer of XhoI endonuclease.

D-Lyxose as a substrate for Streptomyces D-xylose isomerase

Results are presented which show that the D-xylose isomerases present in Streptomyces olivaceus and Streptomyces phaeochromogenes NRRL B-3559 are incapable of utilizing D-lyxose as a substrate. The implications of these findings as related to the use of D-lyxose in the selection of constitutive mutants are discussed.

The possible involvement of a plasmid(s) in actinomycin synthesis by Streptomyces parvulus and Streptomyces antibioticus

The treatment of Streptomyces parvulus and Streptomyces antibioticus with acriflavine or novobiocin resulted in the loss of ability to produce actinomycin. The concomitant loss of ability to form aerial mycelium and the incidence of auxotrophic progeny (S. parvulus) were both low relative to the loss of the antibiotic-producing property. Protoplast fusion induced by polyethylene glycol 4000, using suitable auxotrophic strains of S. parvulus, resulted in high recombination frequencies to prototrophy (9.6 approximately 15%). When fusion was carried out between auxotrophic act+ and act- strains, respectively, there was a high frequency (84 approximately 95%) of the actinomycin synthesizing character among the prototrophic recombinants examined. No actinomycin-producing recombinant was detected in similar experiments between auxotrophic non-producing strains.

[Population composition of Actinomyces tumemacerans and Actinomyces albus var. fungatus]

The population analysis of Actinomyces tumemacerans and Actinomyces albus var. fungatus has revealed identical homologous series of spontaneous variants, this suggesting the genetical relationship of the cultures. Variants of the same type (basic, oligosporous, asporogenous and proactinomycete-like) are identical not only according to their individual properties (Kuznetsov, 1973) but also in total characteristics typical of the variants of a given species. Populations of the studied cultures comprise variants synthesizing several antibiotics, i.e. albofungin, albonursin and tetraene (basic and oligosporous variants), albofungin and tetraene (asprogenous green variants), as well as variants producing only one tetraene antibiotic (proactinomycete-like variants). Therefore, the population analysis based on the law of homologous series in hereditary variability of actinomycetes can be used as a new approach to the taxonomy of these microorganisms.

Conditions for the appearance of adifferentiated nocardioform variants of Streptomyces roseoflavus var. roseofungini

It was shown that adifferentiated nocardioform variants (NV) of Streptomyces roseoflavus var. roseofungini 1128 may appear in mycelial cell suspensions of submerged actinomycete cultures in water, phosphate buffer, and water with fructose (1%) or glucose (1%), as well as in mycelia of old (10-30 days) cultures on different carbon sources. When sugars, alcohols, or amino acids were added to a medium with fructose, NV formation was inhibited, but not completely suppressed. Fructose was shown to be the most potent factor in the appearance of NV.

[Detection of plasmids in actinomycetes that produce oxytetracycline and neomycin]

Crude preparations of DNA isolated from Act. rimosus 907, an oxytetracycline-producing organism and Act. fradiae 676, a neomycin-producing organism were analyzed with electrophoresis in agarose gel followed by electron microscopic analysis of DNA isolated from the gel. It was found that Act. rimosus and Act. fradiae contained ring molecules of DNA with the molecular masses of 37 . 10(6) and 59 . 10(6) dalton respectively.

Mutagenicity of dichlorvos and other structurally related pesticides in Salmonella and Streptomyces

The following pesticides: azinphosmethyl, diallate, dichlorvos, EPTC, fenchlorphos, mevinphos, monocrotophos, noruron, parathionmethyl, triallate, trichlorphon and vegadex were tested for the ability to induce his+ revertants in four histidines requiring strains of Salmonella typhimurium--TAI 535(missense), TAI 536, TAI 537 and TAI 538 (frame-shift)- and resistance to low levels of streptomycin in Streptomyces coelicolor. Dichlorvos, which is a phosphoric ester with a dichlorovinyl group as side chain, and trichlorphon, which is known for its spontaneous conversion in dichlorvos, are both mutagenic in Salmonella (strain TAI535) and Streptomyces. Five organophosphorus pesticides similar to dichlorvos but devoid of the vinyl group are not mutagenic. Three carbamates, diallate, triallate and vegadex, which contain a chloroallyl group similar to the vinyl group of dichlorvos are mutagenic in Streptomyes; triallate and vegadex are powerful mutagens also in Salmonella (strain TAI535); two other carbamates devoid of the chlorinated group are not mutagenic. The results suggest that the presence of a vinyl chloride or allyl chloride group in the molecule of these pesticides is responsible for the ability to induce point mutations in Salmonella and Streptomyces.

Chloramphenicol resistance in Streptomyces coelicolor A3(2): possible involvement of a transposable element

The transfer of a Chl element, causing resistance to chloramphenicol in Streptomyces coelicolor A3(2), was studied in NF x SCP1- superfertile crosses. When the Chl element is on the donor side (NF) its transfer to the recombinant cells was virtually total as if the element acted as a second concomitant transfer origin. When the Chl element was on the recipient side (SCP1-) it was never displaced by the immigrant chromosome even when the region facing chl+ was selected for. A fraction of the original Chl- mutants presented a requirement for arginine (ArgB-). A Chl- mutant gave rise spontaneously to ArgB- derivatives at high frequency. The same ArgB- requirement come out at high frequency among Chl- derivatives from a cross NFChl- x SCP1-Chl+ in which neither parent required arginine or produced spontaneously arginine-less derivatives. It is suggested that the Chl element is a "transposable element" (Tn) presumably associated with "insertion sequences" (IS). The insertional inactivation of the Chl element may be accompanied or followed by a deletion in the adjacent ArgB gene.

Interspecies matings of Streptomyces fradiae with Streptomyces bikiniensis mediated by conventional and protoplast fusion techniques

A genetic recombination system for an interspecies mating of Streptomyces bikiniensis with Streptomyces fradiae is demonstrated both by conventional and protoplast fusion methods.

Bacterial protoplast fusion: recombination in fused protoplasts of Streptomyces coelicolor

Numerous recombinants arose when protoplasts of S. coelicolor were treated with polyethylene glycol and regenerated on non-selective solid medium. In six-factor crosses, recombination frequencies of more than 10% (up to 17%) were routinely observed. This recombination did not require either of the known sex factors, SCPI and SCP2. The proportion of multiple crossover classes was much higher than amongst recombinants produced by conjugated between mycelia. Analysis of the spatial distribution of crossovers in double and quadruple crossover recombinants showed only a slight tendency for crossovers to occur closer together than randomly on the complete linkage group. This suggests that genomes brought together by protoplast fusion are complete, or nearly so (in conjugation, in contrast, one genome is represented by a comparatively short fragment). Individual colonies arising from fused protoplasts did not contain different parental genomes without recombinants, but recombinants often occurred without parentals. Several recombinant genotypes often occurred in the same colony, showing a segregation of some, only, of the parental alleles. Complementary genotypes, parental or recombinant, did not occur in the same colony. It is postulated that complete genomes of fused protoplasts usually become fragmented and that crossing-over, often repeated, occurs between the fragments, to generate haploid recombinants. Analysis of fusions between propoplasts of four different genotypes indicated that the average number of protoplasts fusing together was low, but nevertheless appreciable numbers of fusions involved three or four genomes. Crossing-over between them produced recombinants inheriting markers from three or four parents. The generation of nearly random populations of recombinants between two or more parent strains by propoplast fusion under the conditions described appears to have simple applications in industrial and academic strain construction.

Mutants of Streptomyces coeruleorubidus impaired in the biosynthesis of daunomycinone glycosides and related metabolites

Mutants of Streptomyces coeruleorubidus, blocked in the biosynthesis of anthracycline antibiotics of the daunomycine complex, were isolated from the production strains after treatment with UV light, gamma-radiation, nitrous acid, and after natural selection; according to their different biosynthetic activity the mutants were divided into five phenotypic groups. Mutants of two of these groups produced compounds that had not yet been described in Streptomyces coeruleorubidus (aklavinone, 7-deoxyaklavinone, zeta-rhodomycinone and glycosides of epsilon-rhodomycinone). The mutants differed from the parent strains and also mutually in morphological characteristics but no direct correlation between these changes and the biosynthetic activity could be observed in most cases.

Genetic recombination in Streptomyces fradiae by protoplast fusion and cell regeneration

Conditions for highly efficient genetic recombination in Streptomyces by protoplast fusion are described. Protoplasts of S. fradiae and S. griseofuscus were formed by a modification of the glycine-lysozyme-lytic enzyme method (Okanishi, Suzuki & Umezawa, 1974). Regeneration of cells from protoplasts was monitored throughout the growth cycle and was most efficient when cells of either S. fradiae or S. griseofuscus were taken from the transition phase between the exponential and stationary growth phases. Fusion of protoplasts carrying different auxotrophic or chromosomal drug-resistance markers was achieved by treatment with polyethylene glycol, and high frequencies of stable genetic recombinants were obtained.

Improved yields of daunomycinone glycosides in developmental mutants of Streptomyces coeruleorubidus

When improving Streptomyces coeruleorubidus JA 10092, a producer of antibiotics of the daunomycinone complex, the most active variants were found among isolates of morphological types bld-1 (with a suppressed production of the aerial mycelium on organic media containing glucose) and whi (with an asporogenic aerial mycelium on glucose media and with the bald phenotype on media containing starch). Submerged cultures of the whi mutants produced increased quantities of daunomycinone glycosides in the antibiotic complex, the amount of free anthracyclinones being simultaneously decreased. The whi strains differed from the wild type also in higher demands for aeration, concentration of glucose and in an increased production capacity in starch media. The overall antibiotic activity increased more than 40 times after a six-step selection (application of UV light, gamma-radiation, nitrous acid and natural spreads) combined with an altered fermentation technology.