One of the fundamental ways in which organisms communicate with each other is via extracellularly produced chemicals. Living marine surfaces (eukaryotes such as marine macroalgae or invertebrates) are ideal systems in which to explore colonisation by other eukaryotes or microorganisms.

Our research on chemical regulation of colonisation at living marine surfaces has focused on the following topics:

The field of marine chemical ecology has long been dominated by studies of plant/herbivore or predator/prey interactions. Recently we and others in the field have begun to focus on the chemical ecology of fouling (fouling = colonisation of the surface of an organism by the propagules of other organisms).

Using Delisea pulchra as our initial model, we are the first to quantify natural deterrents of fouling (halogenated furanones) on the surface of a marine organism (de Nys, R, et al. (1998) Mar. Ecol. Prog. Ser. 162:79-87) and have in addition explored the anatomical structures of red algae that allow for release of deterrents at the surface of a plant (Dworjanyn et al. (1999) Marine Biology 133:727-736). This has provided an ecologically realistic context for investigations of the detailed mechanisms of interference by furanones in bacterial signalling systems (Fagerlind et al. (2003). J. Mol. Marine Microbiol. €¦) Hentzer et al (2002). Microbiol. 148:87-102, Manefield et al (2002). Microbiol. 148:1119-1127, McDougald et al (2002). Antonie van Leeuwenhoek International Journal of General & Molecular Microbiology 81:3-13, Thompson et al (2002). FEMS Micro Lett. 220:187-195, Webb et al (2003). J. Bacteriol. 185:4585-4592).

Our research on natural antifoulants is now being extended to a broad array of seaweeds and other marine organisms (Steinberg PD, et al. (2001) In Marine Chemical Ecology, Chap 10, JB McClintock and BJ Baker (eds.) CRC Press. pp. 356-387).

Chemical inducers act as cues for settling propagules (larvae, spores, etc.), enabling these planktonic forms to settle in an appropriate habitat for resumption of the benthic (bottom-dwelling) phase of their life history. These cues emanate from marine eukaryotes such as seaweeds, sponges, sea urchins, etc., or from biofilms which are ubiquitous on the ocean floor and on other organisms. Examples include our investigations of settlement cues for the common Australian sea urchins Holopneustes purpurascens and Heliocidaris eryrthrogramma. The cue for the former is derived from one of its algal host plants (Williamson et al. (2000). Biol. Bull. 198:332-245).

The cues for settlement of Heliocidaris are a diversity of bacterial strains that are found in biofilms associated with its habitat. These findings have considerable implications for aquaculture, where inducing localised settlement of the farmed species is one of the major challenges to the industry.

Our research reflects our interests in the chemical mediation of prokayote (bacteria, etc.) / eukaryote (sponges, seaweeds, etc.) interactions. This emergent field represents a unification of the fields of microbiology, natural products chemistry, and marine ecology (e.g., Steinberg et al (2002). Journal of Chemical Ecology 28:1935-1951).

Naturally produced chemicals mediate these interactions at many levels, and in many directions. Metabolites from host eukaryotes inhibit colonisation of bacteria (Maximilien et al. (1998) Aquatic Miocrobial. Ecology. 15:233-246) as well as invertebrate larvae and algal, with consequences on everything from specific bacterial phenotypes to the species composition of bacterial communities. Bacteria on the surface of eukaryotes both induce settlement of other organisms but can also strongly deter settlement (Holmström & Kjelleberg (2000). In: Biofilms: Recent advances in their study and control. Evans L.V. (ed.) Harwood Academic Publishers. pp 101-115). Some naturally occurring bacteria (e.g., Pseudoalteromonas tunicata) are remarkable in their ability to produce inhibitors which specifically target different colonisers (Egan et al (2002. Environ. Mic. 4:433-442). Understanding these marine prokaryote/ eukaryote interactions has implications for the preservation of marine biodiversity and the development of novel antibiotics.