18 - Integrating Dissolved Organic Matter Metabolism and Microbial Diversity: An Overview of Conceptual Models

Abstract

This chapter provides an overview of the principal conceptual models associated with various perspectives on microbial community organization and Dissolved Organic Matter (DOM) processing. The dynamics of heterotrophic microbial communities is a subject long hampered by technological limitations. The complexity and diversity associated with the microbial processing of dissolved organic nutrients has become a large template for research. Two types of models are included in this chapter: “pattern” models and “process” models. These models are classified into three research domains: (1) the community structure domain, (2) the biogeochemical domain, and (3) the trophic domain. The community structure approach has led to the establishment of the biofilm concept and to the realization that DOM structures the whole aqueous environment on a micrometer scale. The biogeochemical approach began with analyses of DOM characteristics, which led to the development of the size-reactivity model and to a steadily improving picture of the mechanics of bacterial nutrient transformation. The trophic approach can be traced to realization of the importance of bacteria in marine food webs—a finding that led to the microbial loop concept, then to a variety of higher resolution models that elucidate the way DOM source dynamics, competition for nutrients, and grazing control bacterial diversity and metabolism. Present models, taken collectively, provide a general picture of the structural and functional organization of bacteria in relation to DOM processing.