1 - Introduction

Abstract

The chapter explains how a distinction has been made between the terms microbial activity and enzyme activity, because enzymes in soil not only originate from microorganisms but also from plants and animals. This book deals with methods in the microbiology, biochemistry, and biotechnology of soil. Soil is a highly complex system that is characterized by a variety of biological, chemical, and physical processes that are markedly influenced by environmental factors. Microorganisms inhabit soil and, together with exocellular enzymes and the soil mesofauna and macrofauna, conduct all known metabolic reactions. Microorganisms play a key role in the decomposition of soil organic matter and nutrient cycling, and therefore, microbial activity is most important for the maintenance of soil fertility. The integrity of the metabolic capacity of the soil microflora is a fundamental requirement for any concept of soil protection, soil bioremediation, and recultivation. Soil microbiology and biochemistry are now considered important fields of the environmental sciences, and reliable methods are required to obtain information on the interactions between microbial populations and environmental factors in soil. Another aspect to be carefully considered in interpreting soil microbial and biochemical measurements is that these assays are generally performed under optimal assay conditions in the presence of substrate to obtain high activity rates. The activity of any enzyme in the soil is due to enzymes that may have a different location. They can be associated not only with proliferating or nonproliferating cells but also with dead cells or cell debris or be immobilized on clays and humic colloids.