Abstract Description

Symbiotic bacteria are pivotal in important ecological processes in the marine environment. In highly biodiverse coral reef ecosystems, a huge biomass thrives in highly oligotrophic water. Bacteria associated with marine sponges play key roles in cycling nutrients, including carbon, nitrogen and phosphorus. Cyanobacteria are important both in nitrogen fixation and in sequestration of phosphorus as polyphosphate, that serves as both an energy and phosphorus reserve. Release of phosphate may be important in providing this key nutrient to other coral reef organisms. Marine invertebrates are a valuable resource for drug discovery and provide leads for new pharmaceuticals. A major challenge is overcoming the “supply problem” for promising compounds. In many cases, the true sources of compounds of interest are symbiotic bacteria. By focusing on culturing and/or genome analysis of these bacteria, the supply bottleneck can be overcome. In the case of the promising anti-cancer compound kahalalide F found in the seaslug Elysia rufescens, we used metagenomics to elucidate production of the compound by a highly specialized obligately symbiotic bacterium found in the algal diet of the seaslug. Microalgae have potential in carbon sequestration by reducing emission of carbon dioxide and producing algal biomass for biofuels and other applications. Symbiotic bacteria can be “probiotics” that improve microalgal growth. Metagenomic analysis revealed two highly novel and specialized Patescibacteria associated with the marine microalga Nannochloropsis oceanica IMET1. The Patescibacteria are new species and genera in a new family and order, providing insights into enigmatic microbial “dark matter” and growth promotion of microalgae.