Introduction

Abstract

The long-term aim of the physiologist in studying the activities of micro-organisms is to explain in chemical terms the living processes of these organisms as they occur in natural environments. Knowledge of the chemical activities of micro-organisms has been steadily accumulating ever since the late seventeenth century when Antonie van Leeuwenhoek first observed micro-organisms. The early microbiologists had no option but to study mixed populations of micro-organisms. Following the work of Brefeld, Lister and Koch, it became possible to study organisms in pure culture, but although this greatly simplified the task of observing and classifying organisms, it meant that they were studied under conditions that were vastly different from those that obtain in natural environments.