Structure of Microbial Mats and Biofilms

Abstract

The application of new technologies, such as confocal scanning laser microscopy and molecular probes, to the study of biofilms and microbial mats has dramatically changed our view of these systems. In particular, the old idea that biofilms are simply microbes suspended in a homogeneous and diffusion limited matrix has been shattered by the realization that this matrix is actually very hydrated and honeycombed with channels. The microbial species which form the microcolonies have been shown to express genes which are not expressed when the organisms are free-swimming. Thus, many models of microbial dynamics based on planktonic studies (e .g., growth, gene exchange, biocide resistance) do not necessarily apply to biofilms . Recent studies of microbial mats have also uncovered some startling phenomenon. For instance, active sulfate reduction has been measured in the oxic zone. The impact of diurnal fluctuations in the environment cannot be underestimated, as species have been shown to migrate within the mat and use totally different metabolic pathways in response to light and oxygen. This review will highlight some of the insights into the biological structure ofbiofilms and microbial mats, and how the structure is affected by the physical and chemical environment, species composition, and species interactions. The chapter begins with a comparison of microbial mats and biofilms and ends with some suggestions for future studies.