Chemical defenses of seaweeds against microbial colonization

Any living or non-living surface immersed in seawater rapidly acquires a bacterial biofilm. For living marine organisms, biofilm formation can result in the death of the host, and thus there is strong evolutionary pressure for marine eukaryotes to evolve mechanisms which inhibit or control the development of biofilms on their surfaces. Some marine eukaryotes are indeed successful in con:rolling biofilms on their surfaces, and in many instances this control is achieved by the production of inhibitory chemicals which act at or near the surface of the organism. In some cases these natural inhibitors are simply toxic to bacteria. However, increasingly it appears that at least some of these compounds act by interfering specifically with bacterial characteristics which effect the ability of bacteria to colonize their hosts, such as attachment, surface spreading, or the production of extracellular macromolecules. As an example, the Australian seaweed Delisea pulchra appears to control bacterial colonization by interfering with a bacterial regulatory system (the acylated homoserine lactone system) that regulates several colonization relevant bacterial traits. Understanding how marine organisms control specific bacterial colonization traits should provide us with insights into new technologies for the control of biofilms on artificial surfaces.