Microbial extracellular enzymes and natural and synthetic polymer degradation in soil: current research and future prospects

摘要

Bacteria and fungi encounter complex organic matter in soil that is a potential source of the energy, carbon, and nutrients that are required for cell maintenance and growth. Cellulose and lignin are two of the most abundant biopolymers in detritus. However, bacteria and fungi do not have the ability to transport these macromolecules into the cytoplasm. Instead they depend on the activity of extracellular enzymes which generate soluble low molecular mass compounds that are recognized by cell wall receptors and transported into the cell. Many organic pollutants in soil are polymeric and poorly soluble (e.g. PAHs, PCBs) or toxic and these also require extracellular catalysis prior to uptake and metabolism. The complexity and diversity of extracellularenzymes and the macromolecules that they degrade will be reviewed and the many locations and multiple fates of these enzymes once they have left the cytoplasm illustrated. The many ways in which extracellular enzymes overcome the destructive or inhibitory properties of the soil matrix and the various strategies that microbes adopt for effective substrate detection and utilization will be described.