Chytridiomycosis of Marine Diatoms-The Role of Stress Physiology and Resistance in Parasite-Host Recognition and Accumulation of Defense Molecules.

Little is known about the role of chemotaxis in the location and attachment of chytrid zoospores to potential diatom hosts. Hypothesizing that environmental stress parameters affect parasite-host recognition, four chytrid-diatom tandem cultures (Chytridium sp./Navicula sp., Rhizophydium type I/Nitzschia sp., Rhizophydium type IIa/Rhizosolenia sp., Rhizophydium type IIb/Chaetoceros sp.) were used to test the chemotaxis of chytrid zoospores and the presence of potential defense molecules in a non-contact-co-culturing approach. As potential triggers in the chemotaxis experiments, standards of eight carbohydrates, six amino acids, five fatty acids, and three compounds known as compatible solutes were used in individual and mixed solutions, respectively. In all tested cases, the whole-cell extracts of the light-stressed (continuous light exposure combined with 6 h UV radiation) hosts attracted the highest numbers of zoospores (86%), followed by the combined carbohydrate standard solution (76%), while all other compounds acted as weak triggers only. The results of the phytochemical screening, using biomass and supernatant extracts of susceptible and resistant host-diatom cultures, indicated in most of the tested extracts the presence of polyunsaturated fatty acids, phenols, and aldehydes, whereas the bioactivity screenings showed that the zoospores of the chytrid parasites were only significantly affected by the ethanolic supernatant extract of the resistant hosts.

Characterisation of hyaluronic acid and chondroitin/dermatan sulfate from the lumpsucker fish, C. lumpus.

The lumpsucker, Cyclopterus lumpus, a cottoid teleost fish found in the cold waters of the North Atlantic, and North Pacific, was identified as a possible source of GAGs. The GAGs present in the C. lumpus dorsal hump and body wall tissue were isolated and purified. Two fractions were analysed by NMR and their GAG structures determined as hyaluronic acid and CS/DS chains. The latter fraction contained GlcA (65% of the total uronic acids) and IdoA (the remaining 35%). All uronic acid residues were unsulfated, whilst 86% of the GalNAc was 4-sulfated and 14% was 6-sulfated. The presence of GlcA-GalNAc4S, IdoA-GalNAc4S and GlcA-GalNAc6S disaccharide fragments was confirmed. The isolated GAGs obtained from each tissue were biochemically characterised. The lumpsucker offers a high yield source of GAGs, which compares favourably with other sources such as shark cartilage.