Microbial Enzymatic Degradation and Utilization of Organic Matter

Abstract

The most significant contribution of microbial ecology, which altered the principles of a current concept in aquatic science, was the recognition that heterotrophic microorganisms play a dominant role in the cycling of organic and inorganic matter and that a large fraction of primary production is not consumed directly by herbivorous consumers but is transformed into bacterial biomass (Lovell and Konopka 1985, Chrost and Rai 1993; Chapter 5, this volume) and then channeled to phagotrophic microorganisms (Sanders and Porter 1988). The above studies led to the idea of the “microbial loop” (Azam et al. 1983; Chapter 12, this volume) and to the discovery that aquatic food chains include a higher number of trophic levels than hitherto believed (Fenchel 1987, Pomeroy and Wiebe 1988). Therefore, the view of the role of microorganisms in aquatic ecosystems has changed significantly in the last decade. In some respects, the change is sufficiently dramatic to make some authors speak about a “change in paradigm” (Williams 1981). Nowadays we recognize that heterotrophic bacteria not only are the major users of organic carbon but also form microbial food webs that transfer energy more efficiently through the aquatic ecosystems than do classical food chains.