ABSTRACT
This chapter explores the consequences of the recalcitrance of lignin to microbial degradation in the absence of molecular oxygen. Lignin evolved as a major structural polymer of vascular plants and functions to impart rigidity to cell walls, decrease water permeation across the cell walls of xylem tissue, and impede microbial invasion of plant tissue. The structure of lignin serves to illustrate the chemical and physical complexity and the structural uniqueness of natural lignins. The three dimensional lignin polymer is formed as a result of the enzymatic coupling of aromatic alcohols. The microbial degradation of aromatic compounds in anaerobic environments is of no less importance to carbon cycling in the biosphere or ecological strategy management than is the biological oxidation of these substrates in aerobic environments. In terms of global significance, anaerobic wetlands and sediments of marine and fresh-water envrionments represent a major site for carbon mineralization in nature and a major sink for deposition of society’s chemical wastes.
