Introduction

This chapter highlights the occupation of spatially, temporally, and genotypically heterogeneous space as a good description of the majority of microbial habitats. The majority of microcosms are closed or partially closed systems, where time-dependent changes in the physical, chemical, and biological properties of the system are seen. The difference between model and microcosm can, for some people, epitomize the difference between an essentially reductionist approach to understanding ecology on the one hand, and a holistic approach on the other. Once the importance of spatial heterogeneity is recognized, one is forced to accept the need for simple laboratory systems which incorporate heterogeneity factors. The chapter discusses a few spatially heterogeneous ecosystems, hopefully to illustrate just where laboratory models may have a useful part to play. The addition of a solid phase to aquatic systems adds considerably to its complexity and to its potential for heterogeneity. The chapter also presents an overview of the key concepts discussed in this book.