ABSTRACT
The wide applicability of 14C-based lignin biodegradation assays to lignin-related research problems is obvious. The importance of bacterial groups in processes of lignin degradation and transformation must be reevaluated in light of studies of bacterial decomposition of 14C-based lignins. Radioisotopic biodegradation assays should become valuable tools to microbial ecologists who wish to examine activities of natural populations of lignin-decomposing microorganisms in ecosystems such as the forest floor. Probably the most useful of nonisotopic techniques for following lignin biodegradation in natural lignocelluloses has been the so-called soil block procedure, which is still in use in many laboratories. Substrates such as cellulose or glucose served as cosubstrates for lignin degradation. Lignin is biosynthesized in vascular plants by a branching sequence of reactions, beginning with CO2 and H2O and proceeding by way of the aromatic amino acid, phenylalanine. Incorporation of 14C-phenylalanine into plant proteins poses somewhat more of a problem than incorporation into polysaccharides.
