Mucor Flavus Research Articles

Sulphur oxidation by soil fungi including some species of mycorrhizae and wood-rotting basidiomycetes

The mycorrhizal fungi Amanita muscaria, Paxillus involutus, Hymenoscyphus ericae, Pisolithus tinctorius, Rhizopogon roseolus, and Suillus bovinus oxidized elemental sulphur to thiosulphate and sulphate in vitro. In some, but not all cases, tetrathionate was also formed. Limited oxidation of elemental sulphur by R. roseolus also occurred when growing in association with Pinus contorta in unsterilized peat. Although yeasts capable of oxidizing sulphur could not be isolated from a wide range of soils, a yeast-like fungus (Monilia sp.) isolated from deciduous woodland soil oxidized elemental sulphur to sulphate, forming thiosulphate, but not tetrathionate. This fungus also oxidized tetrathionate to sulphate but showed only limited ability to oxidize thiosulphate to tetrathionate. Both Aspergillus niger and Trichoderma harzianum oxidized elemental sulphur in mixed culture with Mucor flavus. Larger amounts of sulphate were initially formed in mixed, compared to single culture; but by week 5 of the incubation period sulphate formation was greatest in single culture. The wood-rotting fungi, Hypholoma fasciculare and Phanerochaete velutina showed a limited ability to oxidize elemental sulphur in vitro but were incapable of oxidizing the element when growing as mycelial cords in non-sterilized soils. The relevance of these results to the possibility that fungi play a role in sulphur oxidation in soils is commented upon.

Adsorption of insoluble compounds by mycelium of the fungus Mucor flavus

Mycelium of Mucor flavus Bainier adsorbed calcium silicate, elemental sulphur, lead sulphide and zinc dust from water suspension. The fungus also adsorbed ochre (ferric hydroxide) from acid mine drainage. Ochre adsorption occurred optimally at 25°C and increased with increasing proportion of mycelium to ochre. The addition of a carbon source to the mine drainage on the other hand resulted in a decrease in the amount of ferric hydroxide adsorbed. Aspergillus niger, Fusarium solani and Penicillium notatum also adsorbed ochre, but much less effectively than did M. flavus. The possible industrial applications of this phenomenon are commented upon.

Sulphur oxidation by fungi

Aspergillus niger oxidized elemental sulphur in vitro to form relatively large amounts of sulphate, initially producing thiosulphate, but not tetrathionate. Growth was inhibited by thiosulphate, but not by elemental sulphur, although both were oxidized to sulphate. Mucor flavus also oxidized elemental sulphur, but while it produced less sulphate than A. niger , it consistently formed both thiosulphate and tetrathionate. Substantial sulphur oxidation by Trichoderma harzianum occurred only when large amounts of sucrose were provided, but it was able to oxidize elemental sulphur in autoclaved soil and to use straw to support sulphur oxidation in vitro. The relevance of these findings to the oxidation of sulphur in soils by fungi is discussed.