"This proposal deals with the cultivation of the symbiotic bacteria that are associated with marine sponges. Marine sponges belong to richest and most diverse organisms with respect to their symbiotic microbial population. In addition, marine sponges belon g to the most interesting natural sources of metabolites with anticancer activity. From a number of the most promising metabolites it has been established that they are actually produced by the bacterial symbionts. Currently, less than 1 % of the symbionts can be cultured, and herein lies the challenge. Up to now, attempts to culture these bacteria have been limited to standard cultivation on marine agar plates. For this project a systematic approach for the cultivation of these bacteria is proposed. The mi croenvironments inside the sponge (the mesohyl [=the space between the exo- and endopinacoderm that is consolidated with collagen fibres and silicious spicules], channels and the outer surface), where the bacteria reside, will be mimicked. This will be don e by testing a matrix of cultivation set-ups and environmental conditions in order to cultivate as many different symbionts as possible. Cultivation set-ups that will be assessed are for example marine agar plates coated with sponge collagen and lectins to simulate the mesohyl or a hollow fibre-type of bioreactors to mimic the sponge channels. Environmental conditions that will be tested are for example hyperbaric and anaerobic conditions that occur at certain places of the sponge mesohyl, or the addition o f specific bacterial signal molecules, such as acyl homoserine lactone.The special focus in this project will be on the cultivation of the bacterial population of the marine sponge Axinella corrugata, the producer of the potent anticancer molecule stevensi ne. Stevensine is suspected to be a product of a symbiotic bacterium and research effort will be invested to identify this strain and optimise its cultivation to produce significant amounts of the product."
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