Use of Streptomyces sp. 26-115 protoplasts inactivated by heating in fusion experiments

When heated at 55 degrees C for 30 or 60 minutes protoplasts of auxotrophic mutants of Streptomyces sp. 26-115 producer of actinomycin C (active and inactive variants) lost their capacity for regeneration. The protoplasts heated at at 55 degrees C for 30 minutes and not for 60 minutes maintained some ability to yield recombinants on fusion under the effect of PEG 6000. Unlike the parent active strain, the colonies formed by the spores of the prototrophs yielding on fusion of the intact protoplasts showed wide ranges of antibiotic activity against M. flavus while a significant part of the colonies was inactive. The use of the inactive variant protoplasts heated at 55 degrees C for 30 minutes in the fusion procedure increased the proportion of the inactive variants.     

Preparation and characteristics of protoplasts from various strains of Streptomyces roseoflavus var. roseofungini]

It was shown that the variants of the roseofungin-producing organism, which differ in their differentiation, antibiotic activity, structure and cell wall composition had different sensitivity to the protoplasting factors. The protoplasting increased the population heterogeneity: in strain 1128 it was evident from an increased frequency of the secondary colonies, in variant 1-68, folding of the colonies increased and their consistency become milder, sectorial colonies and colonies with coremia formed. It was in principle possible to transform the protoplasts of S. roseoflavus var. roseofungini by plasmid DNA, which suggests that the roseofungin-producing culture may be useful in genetic engineering.     

Studies of protoplast fusion in Streptomyces chrysomallus

Conditions for the regeneration of cells from protoplasts of Streptomyces chrysomallus, a producer of the peptide antibiotic actinomycin, are described. Regeneration of fusion products was most efficient at 27-30 degrees C on regeneration R2 medium (Okanishi et al., 1974) containing 0.25 M-sucrose. The addition of phosphate (150-300 mg 1(-1) to the medium and incubation at 23 degrees C proved to be optimal for the regeneration of individual strains. Highest recombination frequencies after protoplast fusion were obtained by fusing protoplasts in the presence of 45% (w/v) polyethylene glycol 6000. With strains that produce no, or little antibiotic, protoplasts must be present in excess in fusion mixtures in order to overcome inhibition of regeneration by the antibiotic-producing partner.     

Effect of the composition of reversion medium on change of Staphylococcus aureus lysostaphin protoplasts to coccal forms and L-forms

The experimental conditions under which protoplasts of Staphylococcus aureus strain MS353 (pCp) are converted to the coccal or L-form were investigated. Protoplasts prepared by treating coccal MS353 (pCp) strain with Lysostaphin formed various types of colonies (coccal form, L-form and mixed types) in about 50% yield when they were plated on reversion (R) medium consisting of 2% brain heart infusion, 0.5M sodium succinate, 0.01% bovine serum albumin, 20 mM MgCl2 and 0.6% agar. The L-form type colonies with a typical fried-egg appearance that developed on the R medium at an early stage gradually reverted to the coccal form through a mixed type stage in which a high density area first appeared in the periphery of the colony and then spread throughout the colony. The use of modified R medium without MgCl2 or R medium in which 0.5M sodium succinate as an osmotic stabilizer was replaced by 7.5% NaCl resulted in marked delay in the appearance of reverted cells. R medium without bovine serum albumin yielded atypical L-form type colonies, which contained masses of coccal cells with very irregular margins. On the other hand, R medium without MgCl2 but with penicillin G supported development of L-form type colonies at high rate (13-15%) from the inoculated protoplasts.     

Synergistic defense system by cooperative natural effectors against metastasis of B16 melanoma cells in H-2-associated control: different behavior of H-2+ and H-2- cells in metastatic processes

H-2+ and H-2- cells of B16 melanoma were established by repeated fluorescence-activated cell sorting. The H-2- line formed no metastasis in untreated C57BL/6 mice, whereas the H-2+ cells showed evidence of metastatic development. This difference was ascribed mainly to the increased susceptibility of H-2- cells to attack by natural effector mechanisms, particularly asialo GM1+ NK cells. After treatment with both anti-asialo GM1 serum and whole body irradiation (400 rad), numerous colonies of H-2- cells formed in the lung, whereas the metastasis was only marginally enhanced by irradiation and moderately by treatment with anti-asialo GM1 serum. With the H-2+ cells, treatment with each modality significantly increased the number of metastatic colonies. Therefore collaboration of asialo GM1+ NK cells and radiosensitive natural effectors seems to be the main mechanism involved in the synergistic effects on defense against H-2- cell metastasis, and to a lesser extent against H-2+ cell metastasis. Irradiation (1000 rad) to the right lung to abrogate the organ-associated defense increased the colonies, particularly in the H-2+ cells. On the other hand, treatment with anti-asialo GM1 serum increased colonization in the early phase of metastasis with H-2- cells and may have abolished asialo GM1+ NK cells capable of recognizing the reduced expression of H-2 antigens and eliminating H-2- cells in the blood-born phase. Natural defense mechanisms probably exert suppressive effects on the metastasis of H-2+ cells, mainly in the organ-associated phase after extravasation.     

Enhanced H-2 expression and T-cell-dependent rejection after intracerebral transplantation of the murine lymphoma YAC-1

The relationship between MHC class I (H-2) expression and tumorigenicity was investigated after intracerebral inoculation of the murine lymphoma YAC-1 and its H-2 negative variant, A.H-2-. YAC-1 was less tumorigenic than A.H-2- in normal as well as NK-depleted syngeneic A/Sn mice. However, in T-cell-depleted syngeneic mice YAC-1 was as tumorigenic as A.H-2-. Following intracerebral growth, the H-2 expression of YAC-1 was markedly enhanced in a similar fashion as after intraperitoneal passage. The A.H-2- variant remained H-2 negative after intracranial passage. The H-2 negative variant cells were not rejected from the brain even when intermixed with wild-type YAC-1 cells prior to intracerebral inoculation, excluding an "innocent bystander" effect. In vitro, the intracerebrally passaged YAC-1 line showed enhanced sensitivity to lysis by H-2 Kk Dd (H-2a) specific CTLs but decreased sensitivity to NK cells. The A.H-2- line was unchanged. Our data suggest that the lack of H-2 molecules may facilitate the growth of antigenic tumor cells in the brain due to escape from T-cell-mediated immunosurveillance. Our data also suggest, in line with other recent findings, that intracerebrally growing tumor cells are sheltered from NK cell-mediated rejection.     

Cytologic control of protoplast formation and regeneration in Streptomyces erythraeus, strain BTCC-2

Experiments on protoplast formation and regeneration in S. erythraeus, strain BTCC-2 (Saccharopolyspora erythrae) were performed under microscopic control at all the stages. It was shown that the highest protoplast titer was provided by the mycelium grown in one step in the absence of glycine. For characterizing the protoplasts formed by the mycelium grown under different conditions, their regeneration capacity was estimated by microscopic examination of the protoplasts after 15-20-hour growth in microchambers and evaluation of the regeneration efficiency 7-10 hours later. Of interest was the fact of spontaneous development of colonies consisting of the protoplast-like cells (L-cells) in 15-20 hours. Such colonies were formed only by the protoplasts grown from the mycelium incubated in one step in the absence of glycine or in the presence of 0.1 per cent of glycine. Such conditions provided also the maximum efficiency of the protoplast regeneration. The long-term storage of protoplasts led to a decrease in their viability.     

Cell fusion between L-forms and protoplasts of Staphylococcus aureus

Mixtures of various combinations of Lysostaphin protoplasts and stable L-forms of Staphylococcus aureus, which have different markers for drug resistance, were treated with polyethylene glycol (PEG) to examine the development of doubly resistant fusion products (fusants). To recover doubly resistant colonies as L-forms, they were incubated in 4.5% NaCl-brain heart infusion (BHI) broth containing penicillin G (PCG) for enrichment culture and cultured in PCG-4.5% NaCl-BHI agar medium (method 1), while to recover doubly resistant fusants as L-forms and coccal forms, they were grown on reversion medium (R medium) which causes reversion of protoplasts or fusants to parent type cells, and then cultured on assay media, i.e., R medium, BHI agar medium or PCG-4.5% NaCl-BHI agar medium (method 2). Under both experimental conditions, doubly resistant fusants developed as L-form cells by PEG treatment of pairs of protoplasts carrying the chloramphenicol (CP)-resistance plasmid and L-forms having chromosomal resistance to streptomycin (SM). In the reverse combinations, i.e., protoplasts showing chromosomal SM-resistance and L-form cells carrying the CP-resistance plasmid, the first method gave no doubly resistant colonies. By the second method, without enrichment culture on R medium, the latter combination gave doubly resistant fusants as L-form, coccal-type and mixed-type colonial forms, while when the PEG-treated mixture was enriched on R medium, fusants were obtained exclusively as the coccal type on either R medium or BHI agar assay medium. Neither of the methods yielded colonies of doubly resistant fusants on PEG-treatment of pairs of protoplasts and L-forms both of which were chromosomal, but with different drug resistances. These results show that PEG-induced cell fusion between protoplasts and L-forms of S. aureus, unlike the fusion between protoplasts or between L-forms, resulted in transfer of the drug resistance controlled by the plasmid to the fusion products. The fusants obtained were L-forms in method 1, and coccal type in the method 2.     

Study of the inactivation of antibiotics by bacterial colonies

A procedure of bacteria application to disks from the colonies was used for determining antibiotic inactivation in the disks by the bacteria colonies after the disk direct contact with the colonies. Changes in the antibiotic activity in the disks were registered after incubation at 37 degrees C for 2 hours. It was shown that ampicillin resistant strains of E. coli K12 carrying R plasmids and strains of S. typhimurium and S. aureus inactivated the antibiotics in the disks and their population were homogenous in this respect. It is advisable to use the procedure in assaying drug resistance of bacterial populations.     

Site-directed mutagenesis of histidine residues in Clostridium perfringens alpha-toxin.

Mutagenesis of H-68 or -148 in Clostridium perfringens alpha-toxin resulted in complete loss of hemolytic, phospholipase C, sphingomyelinase, and lethal activities of the toxin. These activities of the variant toxin at H-126 or -136 decreased by approximately 100-fold of the activities of the wild-type toxin. Mutation at H-46, -207, -212, or -241 showed no effect on the biological activities, indicating that these residues are not essential for these activities. The variant toxin at H-11 was not detected in culture supernatant and in cells of the transformant carrying the variant toxin gene. Wild-type toxin and the variant toxin at H-148 bound to erythrocytes in the presence of Ca2+; however, the variant toxins at H-68, -126, and -136 did not. Co2+ and Mn2+ ions stimulated binding of the variant toxin at H-68, -126, and -136 to membranes in the presence of Ca2+ and caused an increase in hemolytic activity. Wild-type toxin and the variant toxins at H-68, -126, and -136 contained two zinc atoms in the molecule. Wild-type toxin inactivated by EDTA contained two zinc atoms. These results suggest that wild-type toxin contains two tightly bound zinc atoms which are not coordinated to H-68, -126, and -136. The variant toxin at H-148 possessed only one zinc atom. Wild-type toxin and the variant toxin at H-148 showed [65Zn]2+ binding, but the variant toxins at H-68, -126, and -136 did not. Furthermore, [65Zn]2+ binding to wild-type toxin was competitively inhibited by unlabeled Zn2+, Co2+, and Mn2+. These results suggest that H-68, -126, and -136 residues bind an exchangeable and labile metal which is important for binding to membranes and that H-148 tightly binds one zinc atom which is essential for the active site of alpha-toxin.     

Isolation and culture of protoplasts from cotyledons of Pinus coulteri D. Don.

A protocol was developed for the isolation and culture of protoplasts from the cotyledons of seedlings of Pinus coulteri D. Don. Incubation of cotyledon pieces in a mixture consisting of cellulase Onozuka R10 2%, Pectolyase Y-23 0.1%, mannitol 10%, CaCl₂ 500 mg/l and other macro and micro-nutrients yielded viable protoplasts. After 24 hours of culture in a complex nutrient medium, the protoplasts regenerated new cell walls and the first divisions were observed within 7–10 days. Small cell colonies were formed within 15–20 days, but these started to accumulate phenolics and no further growth of the colonies was observed.     

Stable transformation of sugarbeet protoplasts by electroporation

Conditions were optimized for the culture, antibiotic selection and stable transformation by electroporation of suspension culture protoplasts of sugarbeet,Beta vulgaris L.. Highest plating efficiencies (up to 65% at day 21) were obtained if protoplasts were cultured in PGO salts (de Greef and Jacobs, 1979) supplemented with 0.1 mg/1 2,4-D, 0.01 mg/l BAP and 9% mannitol, and in 0.6% agarose rather than in liquid medium. Sensitivity to kanamycin also depended on whether protoplasts were cultured in liquid or agarose medium. Stable transformation of protoplast-derived colonies, as determined by resistance to kanamycin and Southern blot analysis, was achieved by electroporation using both rectangular and exponentially-decaying pulses.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - BAP 6-benzylaminopurine - npt-II neomycin phosphotransferase - EDTA ethylenediaminetetracetic acid - SDS sodium dodecyl sulphate     

Wheat protoplast culture: embryogenic colony formation from protoplasts

Wheat (Triticum aestivum L. cv Chinese Spring) protoplasts were isolated from immature embryos or embryogenic calli (3–4 weeks of culture on MS medium with 32 mg/1 dicamba) and cultured in R2 medium containing 2 mg/1 2,4-D by the nurse culture methods originally developed for rice protoplasts (Kyozuka et al. 1987). Protoplasts isolated from embryogenic calli started to divide within 3–5 days and formed colonies at frequencies up to 2% after 3–4 weeks of culture, while protoplasts isolated from immature embryos formed colonies at much lower frequency (less than 0.1%). Some of these colonies were embryogenic, and they appeared at a frequency of approximately 0.5% of colonies formed when callus-derived protoplasts were used. From two of those embryogenic colonies, calli were regenerated and albino shoots and roots were obtained.     

Isolation and culture of protoplasts from high anthocyanin-producing callus of sweet potato

Optimum conditions for the isolation and culture of protoplasts from high anthocyanin-producing callus of sweet potato (Ipomoea batatas) were investigated. Growth phase of callus and the ratio of callus-enzyme solution affected the yield of protoplasts. Composition of the medium and protoplast density were examined for protoplast culture.Small colonies were regenerated from the protoplasts. Upon transfer to light a high amount of anthocyanin was accumulated in these colonies.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - MES 2-(N-morpholino)-ethanesulfonic acid     

A protoplast to plant system in roses

High yields of protoplasts were isolated from embryogenic suspension cultures of Rosa persica x xanthina and Rosa wichuraiana using an enzyme mixture comprising 20 g l^-1 cellulase Onozuka R10, 1 g l^-1 Pectolyase Y-23 and 10 g l^-1 hemicellulase. Agarose-immobilized protoplasts gave the most consistent growth at a plating density of 5×10⁴ protoplasts ml^-1 on the basic medium of Kao & Michayluk (KM8p) containing 2 mg l^-1 naphthaleneacetic acid and 1 mg l^-1 benzylaminopurine. At 25°C in the dark, 0.004% of R. persica x xanthina protoplasts developed into colonies. Using similar culture conditions, but with a plating density of 9×10⁴ protoplasts ml^-1, 0.017% of R. wichuraiana protoplasts developed into colonies. On transfer of R. persica x xanthina colonies to Schenk & Hildebrandt's medium containing 3 mg l^-1 2,4-dichlorophenoxyacetic acid, globular and later stage embryos were formed. Approximately 30% of these embryos developed into plantlets on transfer to basal Schenk & Hildebrandt's medium. Further development of the plantlets took place on cellulose plugs (Sorbarods) soaked in Murashige & Skoog's medium containing 0.05 mg l^-1 naphthaleneacetic acid, 0.05 mg l^-1 indole-3-butyric acid and 0.1 mg l^-1 benzylaminopurine. Rose breeding is now open to the full range of in vitro genetic manipulation techniques involving protoplast technology.     

O-acetyl-salicylic acid promotes colony formation from protoplasts of an elite maize inbred

The salicylic acid derivative acetylsalicylic acid (ASA) was found to promote colony formation from protoplasts isolated from embryogenic suspension cultures of an elite maize inbred line. The drug was most effective at concentrations of 30–100 mg/l, and increases of more than 20-fold in the number of colonies recovered from protoplasts were obtained. The rate of growth of protoplast-derived cell colonies was not affected.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - DMSO dimethylsulfoxide - KM Kao and Michayluk medium (1975) - MES 2[N-morpholino]ethanesulfonic acid - ASA acetylsalicylic acid     

Culture of soybean mesophyll protoplasts in alginate beads

Mesophyll protoplasts were isolated from leaves of 10 day old aseptically grown soybean seedlings, or from surface disinfested leaves of 3 week old plants grown in environmental chambers. The protoplasts were encapsulated in 2mm diameter Ca alginate beads. Immobilized protoplasts were induced to divide by culturing in shaker flasks containing an actively growing soybean cell suspension. The feeder cell suspension supported the division of protoplasts independent of the protoplast density in the Ca alginate beads. At day 18 after encapsulation, the alginate matrix was dissolved, releasing viable callus colonies. The feeder cell suspension obviated plating of protoplasts at high density which is usually required for subsequent cell division and colony development. Since the protoplasts were embedded at low density, the cell colonies were derived from single cells.     

Analytical Studies on Regeneration of Protoplasts of Geotrichum candidum by Quantitative Thin-Layer-Agar Plating

A preparation of pure protoplasts of Geotrichum candidum became osmotically stable and colonies developed when the protoplasts were embedded in stabilizing thin-layer-agar and incubated with stabilizing basal medium. When growing protoplasts were exposed to distilled water and then reincubated with basal medium, the process of regeneration of protoplasts could be quantitatively demonstrated by counting colonies. The process was divided into three phases, lag, logarithmic, and stationary. Furthermore, the state of regeneration of protoplasts at each phase could be seen in detail by microscopic studies of protoplasts under similar growth conditions. In the lag phase, which lasted for 2 hr after inoculation, protoplasts were completely destroyed when placed in distilled water. During the logarithmic phase, from 2 to 5 hr after inoculation, protoplasts rapidly became osmotically stable and about 18% of them were growing. In the stationary phase, most protoplasts developed germ tubes within 2 hr. These results suggested that there are two main phases, although individual cells passed through three different conditions, osmotically labile, osmotically stable, and growing. No apparent structure of cell wall material could be detected by electron microscopy on the surface of the membrane of these osmotically stable cells.     

Regeneration of diploid and tetraploid plants from callus-derived protoplasts of Agapanthus praecox ssp. orientalis (Leighton) Leighton

protoplasts was developed for the Liliaceous ornamental plant, Agapanthus praecox ssp. orientalis (Leighton) Leighton `Royal Purple Select' (2n=2x=32).Viable protoplasts were routinely isolated from leaf-derived embryogenic calluses with yields of 0.8 to 1.5x10 protoplasts per g FW of calluses. Protoplasts started to divide 5 to 7 days after isolation, and protoplast-derived colonies consisting of 50 to 100 cells were obtained after 1 month. A plating efficiency of 0.8% was obtained after 2 months of culture using a gellan gum-solidified medium containing 1 mg 1^-1 each of PIC and BA under continuous illumination. Protoplastderived calluses produced somatic embryos at a frequency of 46.7 % on PGR-free medium, whereas 68.3 % of the calluses regenerated adventitious shoots on a medium containing 1 mg 1^-1 BA. Somatic embryos and adventitious shoots developed into plantlets, which were successfully transplanted to pots. Flow cytometric analysis and chromosome observation revealed that both diploid and tetraploid plants were regenerated from protoplasts.     

Plating of isolated tobacco mesophyll protoplasts on agar medium

Summary A technique was developed to derive cell and plant clones from isolated mesophyll protoplasts of tobacco. The protoplasts, plated on a fully defined agar medium, divided and grew actively forming visible colonies after one month of culture. Efficiency of colony formation depended on cell density and light condition during incubation. Under standard conditions, 60% of plated protoplasts formed colonies. Upon transfer onto suitable media, these colonies differentiated shoots and roots, and eventually regenerated whole plants. Advantages of mesophyll protoplasts as the source of clones as well as implication of the plating technique for genetical studies are discussed.