THE ECOLOGY AND PHYSIOLOGY OF SOIL FUNGI INVOLVED IN THE DEGRADATION OF LIGNIN AND RELATED AROMATIC COMPOUNDS

A study has been made of the colonization by soil fungi of kaolin pellets in which was incorporated either a lignin preparation extracted from Phragmites or the lignin-related substances, vanillic acid or α-conidendrol. Fungi isolated from the lignin pellets by the dilution method were grown in liquid culture containing the Phragmites lignin. Subsequent analysis by UV absorption spectrometry indicated up to 40 per cent loss of this material. IR analysis of the residual lignin showed that it was little altered. Fungi from the pellets containing vanillic acid and α-conidendrol were isolated by direct transfer of spores and mycelium from the pellets to agar plates. The range of soil fungi already known to metabolize vanillic acid in pure culture was extended by this method and included Stilbum spp., Humicola sp., and two unidentified species. Dry-weight determinations of mycelia combined with UV absorption spectrometry and paper chromatography of culture filtrates indicated that, with the exception of Acremoniella sp., all isolates metabolized vanillic acid when it was supplied as sole C source. Growth-promoting substances present in yeast extract were required by Volutella spp. before the vanillic acid was metabolized. The pellet technique offers many possibilities for studying the microbiological degradation of soil substances and in addition enables the soil micro-habitats to be explored in greater detail than has previously been possible.