Ramihyphins--antifungal and morphogenic antibodies from Fusarium sp. S-435

Fusarium-Derived Secondary Metabolites with Antimicrobial Effects

Fungal microbes are important in the creation of new drugs, given their unique genetic and metabolic diversity. As one of the most commonly found fungi in nature, Fusarium spp. has been well regarded as a prolific source of secondary metabolites (SMs) with diverse chemical structures and a broad spectrum of biological properties. However, little information is available concerning their derived SMs with antimicrobial effects. By extensive literature search and data analysis, as many as 185 antimicrobial natural products as SMs had been discovered from Fusarium strains by the end of 2022. This review first provides a comprehensive analysis of these substances in terms of various antimicrobial effects, including antibacterial, antifungal, antiviral, and antiparasitic. Future prospects for the efficient discovery of new bioactive SMs from Fusarium strains are also proposed.

The cyclosporins

This review presents the progress and some aspects achieved during recent years with cyclosporin sources, chemistry, biological activities, side effects, biosynthesis and metabolism. Although incomplete the results indicate future research trends and some white spots to be studied in the near future to afford unique insights into cell biology and to improve the search for similar and even more specific agents based on rational drug design.

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.

Yeast cyclophilin: isolation and characterization of the protein, cDNA and gene

Cyclophilin (CPH) has been isolated from the yeast Saccharomyces cerevisiae, purified to homogeneity and partially sequenced. Oligodeoxyribonucleotides deduced from this sequence were used to isolate the corresponding cDNA and gene. An open reading frame coding for a 162-amino acid (aa) protein with a calculated Mr of 17,392, was deduced from the nucleotide sequence. Comparison between yeast and human CPH shows a very high overall sequence conservation (65% aa homology). The binding of yeast CPH to cyclosporin A is identical to that of human and bovine CPH. Unlike in Neurospora crassa, a mitochondrial form of CPH could not be detected in yeast. Southern-blot analysis of yeast DNA shows that only one CPH-related sequence is present per haploid genome, whereas at least 20 genes or pseudogenes were detected in the human and rat genome. Purified yeast CPH exhibits peptidyl-prolyl cis-trans isomerase activity, albeit to a far lesser extent than the mammalian protein.

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.

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.

Effects of cyanein and ramihyphin A on the dimorphism of Paracoccidioides brasiliensis

As a preliminary step in the study of dimorphism in Paracoccidioides brasiliensis, the effects of cyanein and ramihyphin A were studied. These antibiotics have been reported to induce morphological changes in fungi. The results obtained suggest that ramihyphin A induce swelling of hyphae while partially inhibiting Y leads to M transformation with the production of an incipient and swollen mycelium. Cyanein did not affect the mycelial morphology as did ramihyphin A. However, the Y leads to M transformation was inhibited and, also, the M leads to Y transformation was blocked with the production of a few yeast cells which were not released from the mycelium.

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.