Biofilm mediated decontamination of pollutants from the environment

Microbes often construct and live within surface-associated multicellular communities known as biofilms. The precise structure, chemistry and physiology of the biofilm all vary with the nature of its resident microbes and local environment. However, an important commonality among biofilms is that their structural integrity critically depends upon an extracellular matrix produced by their constituent cells. Extracellular matrices might be as diverse as biofilms, and they contribute significantly to the organization of the community. This review discusses recent advances in our understanding of the extracellular matrix and its role in biofilm biology.

Many microorganisms demonstrate resistance to metals in water, soil and industrial waste. Genes located on chromosomes, plasmids, or transposons encode specific resistance to a variety of metal ions. Some metals, such as cobalt, copper, nickel, serve as micronutrients and are used for redox processes, to stabilize molecules through electrostatic interactions, as components of various enzymes, and for regulation of osmotic pressure. Most metals are nonessential, have no nutrient value, and are potentially toxic to microorganisms. These toxic metals interact with essential cellular components through covalent and ionic bonding. At high levels, both essential and nonessential metals can damage cell membranes, alter enzyme specificity, disrupt cellular functions, and damage the structure of DNA. Microorganisms have adapted to the presence of both nutrient and nonessential metals by developing a variety of resistance mechanisms. Six metal resistance mechanisms exist: exclusion by permeability barrier, intra- and extra-cellular sequestration, active transport efflux pumps, enzymatic detoxification, and reduction in the sensitivity of cellular targets to metal ions. The understanding of how microorganisms resist metals can provide insight into strategies for their detoxification or removal from the environment. Copyright 2000 Academic Press.

Bacterial growth and survival in numerous environments are constrained by the action of bacteria-consuming protozoa. Recent findings suggest that bacterial adaptations against protozoan predation might have a significant role in bacterial persistence and diversification. We argue that selective predation has given rise to diverse routes of bacterial defense, including adaptive mechanisms in bacterial biofilms, and has promoted major transitions in bacterial evolution, such as multicellularity and pathogenesis. We propose that studying predation-driven adaptations will provide an exciting frontier for microbial ecology and evolution at the interface of prokaryotes and eukaryotes.