Associations Among Bacteria, Yeasts, and Basidiomycetes During Wood Decay

Abstract

Bacteria, yeasts and basidiomycetes were closely associated during the decay of dead coniferous wood. In the laboratory, significant increases in decay (weight loss) and a marked stimulatory effect on mycelial growth was observed after 5 mo. in wood decay treatments combining bacteria (Enterobacter spp.) and yeasts (Saccharomyces bailii var. bailii and Pichia pinus) with the basidiomycetes, Coriolus versicolor, Hirschioporus abietinus, or Poria placenta. Substrates used were wood chips from slash less than 1 yr, between 1 and 2 yr, and over 25 yr old. The amount of mycelia present was determined quantitatively by assaying for glucosamine. Up to 200% more fungal growth was obtained in treatments combining bacteria, yeasts and a basidiomycete than with single basidiomycetes. Substantially more decay (2- to 10-fold) occurred with the brown-rot fungus, P. placenta, than with the white-rot fungi, C. versicolor or H. abietinus. The age of the chips and the species of wood used affected the rate of decomposition. Decay was more rapid in wood chips from slash less than 2 yr than in that over 25 yr old. Bacteria and yeasts were responsible for increases of decay by the respective basidiomycete in wood chips of all age classes. Scanning electron microscopy revealed mutualistic associations among microorganisms. Bacteria and yeasts were located only in tracheid cell walls decayed by basidiomycetous hyphae. Similar associations of bacteria, yeasts and mycelia were observed in logs naturally infected by 4 basidiomycetes, C. versicolor, H. abietinus, Cryptoporus volvatus and Fomitopsis pinicola.