ABSTRACT
Determining the metabolic function of individual taxa within microbial communities represents a major challenge in microbial ecology. One approach to address this question has first involved the isolation, identification and characterization of microorganisms to which a particular function can be attributed. A functional group can sometimes be defined by small subunit rRNA gene similarities, enabling the subsequent use of molecular biological techniques to investigate these closely related populations in situ (1-3). An analogous approach has defined functional groups on the basis of similarities between genes that encode key enzymes in metabolic pathways, ‘functional genes’ (4-6). It is likely that many microorganisms will share metabolic functions, and therefore some uncultivated taxa will be detected using these molecular approaches. However, not all uncultivated taxa will necessarily share the genetic similarities used to define an individual functional group, and thus the metabolic function and identity of these organisms will remain unclear.
