The Formation of Extracellular Nitrogen Compounds by Fungi

Abstract

SUMMARY: The production of nitrogen compounds in the culture medium by Scopulariopsis brevicaulis and other fungi has been studied. The formation of extracellular nitrogen compounds accompanied the primary assimilation of ammonia, nitrate and organic nitrogen in all experimental conditions so far investigated among the various factors studied. The amount of these extracellular nitrogen compounds was affected markedly only by the supply of certain trace elements. It was lowest when the concentration of trace elements was high, and increased as the concentration of trace elements approached that limiting growth. Most of the extracellular nitrogen appeared to be peptide in nature, yielding some 14 amino acids on hydrolysis. The fungus was unable to assimilate the extracellular nitrogen compounds formed but assimilated the constituent amino acids when these were liberated by acid hydrolysis.When fungi grow on inorganic nitrogen sources organic nitrogen compounds appear in the culture medium at the same time (Morton, 1951). This phenomenon seems to be frequent among micro-organisms; it has been observed in bacteria (Fedorov, 1952;Hotchkiss, 1950; Proom & Woiwod, 1949), in bluegreen algae (Fogg, 1952;Henriksson, 1951 ;Watanabe, 1951) Hartelius (1937) noted in experiments with yeast. This link with primary nitrogen metabolism is the most significant feature of our observations and prompted further investigation. These secondarily formed organic nitrogen compounds which appear in the medium during growth will for the sake of brevity be termed simply ' extracellular nitrogen '. EXPERIMENTALThe fungi used were grown in surface culture in small flasks containing 20 ml. of culture medium of the following basal composition: 50 g. glucose; 1.0 g. KH,PO,; 0-5 g. MgS0,.7H,O; trace elements (200,ug. Fe, 38,ug. Cu, 225,ug. Zn, 24pg. Mn, and 40pg. Mo); water to 11. Different nitrogen sources were added as required. The nitrogen source was always sterilized separately from the other components of the medium in order to avoid any interaction with the carbohydrate present. The pH value of the media was adjusted to 6.5 initially, and the cultures were incubated at 25O.

THE MECHANISM OF MYCELIAL STRAND INDUCTION IN SERPULA LACRIMANS: A POSSIBLE EFFECT OF NUTRIENT DISTRIBUTION

“…Morton and Broadbent (1955) isolated amino acids which had been lost from mycelium and which after purification could be re-utilized. One may speculate that under nitrogen-poor conditions such as those that the fungus must encounter when it is rotting wood, S. lacrimans may derive nitrogen for new growth from older mycelium, and that this might form at least part of the hypothetical leaked substance.…”

Effect of Colchicine on the Mycelial Weight and the Nitrogen and Phosphorus Contents of the Mycelium of Cunninghamella Sp.

“…The rate of secretion increased with the increase in concentration of colchicine, the release being mainly in the peptide form. The release of nitrogen from the mycelial cells into the external media is not uncommon among fungi (7, 8,10,11,12). Since the nitrogen escape started before the exhaustion of the sugar and nitrogen supply in the culture media, i.e.…”

Conditions Relevant to the Occurrence of Acid‐fast Bacilli in Sphagnum Vegetation

“…The coverage never exceeded 30% and apparently has not, by shading, had a negative effect on accumulation of heat. Since a symbiosis between species of Ericaceae and fungi has been established Csurgeff 19611, the high concentration of AFB found where such species were present, may also be due to nutrients produced by fungi (Morton & Broadbent 1955, Bach 1976.…”