Host Mycelium Research Articles

Effect of Nitrogen Nutrition on the Free Amino Acid Pool of Choanephora cucurbitarum and Parasitism by Two Haustorial Mycoparasites

SUMMARYThe susceptibility of Choanephora cucurbitarum to parasitism by the biotrophic haustorial mycoparasites, Tieghemiomyces parasiticus and Piptoccphalis virginiana, was markedly affected by both the nitrogen (N) source and carbon/nitrogen (C/N) ratio in host culture media. Parasitism could not be correlated with host growth or pH of culture filtrates. Analyses of the free amino acid pool in host mycelium by gas-liquid chromatography revealed high concentrations of glutamic acid and to a lesser extent other amino acids when N sources or C/N ratios favorable for parasitism were present in media. Poor N sources for parasitism resulted in low levels of all pool amino acids except those used as the N source. When the C/N ratio was increased in media initially favorable for parasitism, concurrent reductions occurred in levels of free amino acids in host mycelium and in growth of the parasite. Reductions in parasitism could not be correlated to the absence of specific amino acids in the host pool. Axenic growth of T. parasiticus on a glycerol medium amended with the amino acid pool from host mycelium was markedly affected by the N source used in host culture media. Excellent axenic growth occurred after amendment with clarified amino acid extracts from host mycelium cultured in media having a favorable N source for parasitism, whereas poor axenic growth resulted after amendment with extracts from mycelia grown in media having an unfavorable N source. In the fungal host-haustorial mycoparasite relationship, it appearss that the quantitative aspects of the free amino acid pool of the host are a primary determinant of the degree of susceptibility of host mycelium to parasitism.

Effect of Nitrogen Nutrition on the free Amino Acid Pool of Choanephora Cucurbitarum and Parasitism by two Haustorial Mycoparasites

The susceptibility of Choanephora cucurbitarum to parasitism by the biotrophic haustorial mycoparasites, Tieghemiomyces parasiticus and Piptocephalis virginiana, was markedly affected by both the nitrogen (N) source and carbon/nitrogen (C/N) ratio in host culture media. Parasitism could not be correlated with host growth or pH of culture filtrates. Analyses of the free amino acid pool in host mycelium by gas-liquid chromatography revealed high concentrations of glutamic acid and to a lesser extent other amino acids when N sources or C/N ratios favorable for parasitism were present in media. Poor N sources for parasitism resulted in low levels of all pool amino acids except those used as the N source. When the C/N ratio was increased in media initially favorable for parasitism, concurrent reductions occurred in levels of free amino acids in host mycelium and in growth of the parasite. Reductions in parasitism could not be correlated to the absence of specific amino acids in the host pool. Axenic growth of T. parasiticus on a glycerol medium amended with the amino acid pool from host mycelium was markedly affected by the N source used in host culture media. Excellent axenic growth occurred after amendment with clarified amino acid extracts from host mycelium cultured in media having a favorable N source for parasitism, whereas poor axenic growth resulted after amendment with extracts from mycelia grown in media having an unfavorable N source. In the fungal host-haustorial mycoparasite relationship, it appears that the quantitative aspects of the free amino acid pool of the host are a primary determinant of the degree of susceptibility of host mycelium to parasitism.

Host-Parasite Relations in a Mycoparasite IV. A Correlation between the Levels of g-Linolenic Acid and Parasitism of Piptocephalis virginiana

SUMMARYThe amount of γ-linolenic acid found in the mucoraceous host fungus, Choanephora cucurbitarum, is influenced by cultural conditions such as temperature, light, age of the culture, and composition of the growth media. These conditions also affect the degree and rate of development of the parasite, Piptocephalis virginiana. There is a direct correlation between the levels of γ-linolenic acid present in C. cucurbitarum during the early stages of growth (24 hr) and the degree of parasitism of P. virginiana. The amount of γ-linolenic acid present in the host mycelium was found to be unrelated to either dry weight of the mycelium or total lipid contents. Piptocephalis virginiana is confined to host species which are known to contain γ-linolenic acid. The culture filtrate of the host when tested for leakage of fatty acids from the mycelium, showed the presence of all the fatty acids except for γ-linolenic acid. The significance of these findings are discussed in relation to parasitism of P. virginiana.

Mycoparasitism by Stephanoma Phaeospora

SUMMARY Stephanoma phaeospora is a biotropic mycoparasite. It contacts its hosts by means of hook-shaped branches but does not penetrate host mycelium. Of 97 species of fungi tested, 14 were hosts to S. phaeospora; all were in the Ascomycetes or Deuteromycetes, except Ustilago avenae and U. maydis of the Basidiomycetes. Fungi in the Phycomycetes were not hosts. The parasite was deficient for an unknown growth factor, possibly mycotrophein, found in the mycelium of all the test fungi in the Ascomycetes and Deuteromycetes; only a few species of the Phycomycetes and Basidiomycetes produced a detectable amount of this factor. Some fungi, especially in the genus Aspergillus, released the growth factor into the substrate, thus supporting saprobic growth of S. phaeospora. Axenic growth of the parasite was obtained only on media supplemented with the growth factor. A standard curve is presented for bioassay of the growth factor.

Mycoparasitism by Stephanoma phaeospora

SUMMARYStephanoma phaeospora is a biotropic mycoparasite. It contacts its hosts by means of hook-shaped branches but does not penetrate host mycelium. Of 97 species of fungi tested, 14 were hosts to S. phaeospora; all were in the Ascomycetes or Deuteromycetes, except Ustilago avenae and U. maydis of the Basidiomycetes. Fungi in the Phycomycetes were not hosts. The parasite was deficient for an unknown growth factor, possibly mycotrophein, found in the mycelium of all the test fungi in the Ascomycetes and Deuteromycetes; only a few species of the Phycomycetes and Basidiomycetes produced a detectable amount of this factor.Some fungi, especially in the genus Aspergillus, released the growth factor into the substrate, thus supporting saprobic growth of S. phaeospora. Axenic growth of the parasite was obtained only on media supplemented with the growth factor. A standard curve is presented for bioassay of the growth factor.

The life-cycle of an actionophage for Streptomyces venezuelae.

SUMMARY The life-cycle of actinophage MSP 2 in host Streptomyces venezuelae s 13 was divisible into distinct stages by manipulating the cultural conditions and by the use of certain chemical compounds. Two types of attachment were observed: reversible and irreversible. Reversible attachment occurred instantaneously and was relatively independent of temperature and phage concentration. The controlling variables in extent of adsorption were the amount of host mycelium and ionic content of the medium. Irreversible attachment was time dependent and temperature dependent. Addition of acriflavine allowed phage attachment and injection to occur, but suppressed some stage of intracellular growth or maturation. Acriflavine prevented formation of viable phage, but phage components were demonstrated immunologically and electron-microscopically. Chilling of phage-infected cultures allowed lysis to proceed, with release of preformed phages; but no new phages were formed. These results indicate that the life-cycle of actinophage MSP2 is experimentally separable into attachment, injection, growth, maturation and lysis.