Morphogenetic activity of cytochalasins, cyanein, and monorden in Botrytis cinerea

Biological effects of the antibiotic brefeldin A (decumbin, cyanein, ascotoxin, synergisidin): a retrospective

Brefeldin A has been recently characterized to act as an inhibitor of intracellular protein export with profound effects on the structure and function of the Golgi apparatus in animal cells. Manifold activities of the antibiotic (under different names) published in the 1960's and 1970's are reviewed: effects on fungal growth and morphogenesis, inhibition of mitosis in plant cells, cytotoxicity, cancerostatic, antiviral and antinematodal activity and peculiar effects on DNA, RNA and protein synthesis in microbial and animal cells.

Antifungal agents as tools in experimental mycology

Both natural and synthetic substances are conveniently used for studying metabolism, genetic aspects, morphogenesis of cell structures, life cycle and differentiation of fungi.

Biological properties of acmycin, a new polyene antibiotic

Acmycin, a new polyene antibiotic, was fungistatic at low and fungicidal at high concentrations. It produced malformations in conidia of Helminthosporium oryzae and Curvularia lunata and caused leakage of yeast cells. Acmycin was fairly nontoxic to germinating seeds. The intravenous LD50 was 300-400 and intraperitoneal maximum tolerated dose 100-500 mg/kg body mass of mice.

Induction of mycelial type of development in Candida albicans by the antibiotic monorden and N-acetyl-D-glucosamine

Two new effective methods for synchronous germ tube production in Candida albicans have been described. Both are based on the use of stationary grown cultures and their further incubation in an aerated simple mineral medium enriched with vitamins containing either high glucose concentration (100 mmol/1) and the antibiotic monorden being added, or N-acetyl-D-glucosamine (100 mmol/1) as the sole carbon source. On the other hand yeast morphology could be maintained in the medium with high glucose concentration. On the basis of the methods developed it was possible to compare respiration intensity, respiration quotients, and sensitivity against some metabolic inhibitors in both morphological forms. Labeling experiments showed slight differences in the time course of glycine incorporation. The mycelial cell walls contained more chitin than the yeastlike cells. Using light and electron microscopy the interrelationships between concentration of monorden, or N-acetyl-D-glucosamine, physiological state of inoculum and the germ tube frequency were determined. The results are discussed with regard to the induction of germ tubes by low glucose concentration in Candida albicans from the more general aspect of regulation of fungal morphogenesis.

The use of antibiotics for studies of morphogenesis and differentiation in microorganisms

Numerous antibodies with a known mechanism of action are utilized as possible means for studying morphogenesis and differentiation. Inhibitors of biosynthesis of nucleic acids and proteins, compounds intervening with the synthesis and/or function of cell walls and membranes or compounds influencing the energy metabolism are particularly useful. The use of antibiotics for studies of the life cycle of viruses, bacteria, fungi, myxomycetes, protozoa and algae is analyzed in the present communication. Certain aspects of morphogenesis and functions of mitochondria and plastids were clarified with the aid of antibiotics. Relationships between production of antibiotics and differentiation of their producers are discussed in the final part of the paper.

Ophiocordin, an antifungal antibiotic of Cordyceps ophioglossoides

An unknown antibiotic, ophiocordin, C21H22N2O8, MW: 430, was isolated from submerged cultures of Cordyceps ophioglossoides, strain TU 276, grown in a glycerol soybean meal medium at 27 degrees C. The antibiotic was extracted from acidified culture fluids with n-butanol and purified by subsequent column chromatography on DEAE-Sephadex and cellulose. Studies including nuclear magnetic resonance and mass spectrometry resulted in proposals of partial structures of the molecule. Inhibition by ophiocordin could be demonstrated for a small number of fungi belonging to different taxonomic groups. Bacteria were not inhibited. The antifungal effect was antagonized by ammonia and nitrate ions and by certain amino acids.

Antibiotic-induced changes of mycelial growth of Botrytis cinerea

The effect of antibiotics and metabolic inhibitors on mycelial growth of Botrytis cinera was followed. Inhibitors of protein synthesis, chloramphenicol, erythromycin and tetracycline inhibit growth or sporulation of Botrytis cinera. Ethidium bromide, 5-fluorouracil, phenylethylalcohol and K 20 cause granulation, vacuolization and undulation of hyphase. 2,4-Dinitrophenol, boromycin, macrotetrolides, monensin, scopathricin and TX2 at subfungistatic concentrations induce intensive branching of hyphal tips i.e. at the site of synthesis of the cell wall. In older hyphase grown in the absence of the antibiotics the branching begins after their addition, particularly in the septum region. When comparing the results referred to here with those obtained previously and on the basis of literature data it may be assumed that the changes in polarity of growth of Botrytis cinerea might be caused primarily or secondarily by impairing membrane functions and formation of cell walls.

Colonial growth and ramihyphin A-induced changes in cell walls of Neurospora sitophila

Colonial growth of Neurospora sitophila phenotypically induced by ramihyphin A is accompanied by marked changes in the contents of DNA, RNA and proteins in the mycelium, and in the relative proportion of hexoses in cell wall hydrolysates. The glucosamine/glucose ratio is also characteristic for colonial growth. X-ray analysis of cell walls showed that ramilhyphin A suppresses the crystalline arrangement of chitin in cell walls. A combination of microbiological, biochemical and physico-chemical methods yielded a general picture of the changes accompanying the colonial growth of Neurospora sitophila.

Effects of antibiotics on the life cycle of Neurospora crassa

Some antibiotics and synthetic inhibitors affect, in several ways, the life cycle of Neurospora crassa (germination of conidia leads to myceliar growth leads to formation of conidia). Bikaverin, cyanein, scopathricin and phenethyl alcohol retard the germination of conidia, without inhibiting it completely. 5-Fluorouracil, ramihyphin A and zygosporin A (cytochalasin D) do not inhibit the germination. Bikaverin brings about a thickening of the hyphae of growing mycelium. Ramihyphin A, cyanein, scopathricin and zygosporin A stimulate the ramification of hyphae while 5-fluorouracil and phenethyl alcohol do not affect the myceliar morphology apart from their inhibitory effect on growth. Actinomycin D, 5-fluorouracil, cycloheximide, ramihyphin A and partially also sodium iodoacetate inhibit to a different degree the photoinduced formation of conidia. The inhibition by 5-fluorouracil is very conspicuous when the agent is present during the photoinduction but considerably weaker when it is applied 2 h after the photoinduction.

Morphogenic effects of ramihyphin A in filamentous fungi

Ramihyphin A at subfungistatic concentrations stimulates ramification of hyphae of filamentous fungi. Stimulation of terminal ramification of hyphae that can be observed particularly in phytopathogenic fungi is most frequent. Hyphae of Microsporon canis, Trichophyton mentagrophytes, Blastomyces dermatitidis, Coccidioides immitis and Histoplasma capsulatum ramify intensively laterally. Stimulation of the lateral ramification was observed in Monilia fructigena, Penicillium marneffei and Penicillium chrysogenum. The antibiotic induces also formation of vesicular structures in phytopathogens. Due to the substantial ramification of hyphae, both terminal and lateral, the growth of colonies is interrupted. The addition of the antibiotic to a growing colony of Botrytis cinerea induces dichotomic ramification of terminal hyphae after 3 h of growth. Lateral hyphae begin to grow later and further ramify dichotomically. Dense bundles of ramified hyphae are formed after 24 h due to the unbalanced ramification and the colony no longer increases its size.