title: Chytridiomycosis of Marine Diatoms-The Role of Stress Physiology and Resistance in Parasite-Host Recognition and Accumulation of Defense Molecules.
abstract: 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 (Chytridiumsp./Naviculasp.,Rhizophydiumtype I/Nitzschiasp.,Rhizophydiumtype IIa/Rhizosoleniasp.,Rhizophydiumtype IIb/Chaetocerossp.) 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.
authors.affiliation: BioPol ehf., Einbúastig 2, 545 Skagaströnd, Iceland. bettina@biopol.is.|Faculty of Natural Resource Sciences, University of Akureyri, Borgir v. Nordurslod, IS 600 Akureyri, Iceland. bettina@biopol.is.
authors.forename: Bettina
authors.initials: B
authors.lastname: Scholz
authors.affiliation: Oceanlab, University of Aberdeen, Main Street, Newburgh AB41 6AA, Scotland, UK. fkuepper@abdn.ac.uk.
authors.forename: Frithjof C
authors.initials: FC
authors.lastname: Küpper
authors.affiliation: Department of Biology, Section of Protistology and Aquatic Ecology, University of Ghent, Krijgslaan 281 S8, 9000 Ghent, Belgium. wim.vyverman@ugent.be.
authors.forename: Wim
authors.initials: W
authors.lastname: Vyverman
authors.affiliation: BioPol ehf., Einbúastig 2, 545 Skagaströnd, Iceland. halldor@biopol.is.
authors.forename: Halldór G
authors.initials: HG
authors.lastname: Ólafsson
authors.affiliation: Institute of Biological Sciences, Applied Ecology & Phycology, University of Rostock, Albert-Einstein-Strasse 3, 18059 Rostock, Germany. ulf.karsten@uni-rostock.de.
authors.forename: Ulf
authors.initials: U
authors.lastname: Karsten
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000382:microbiology / Q000502:physiology*; D002633:Chemotaxis / Q000502:physiology; D008411:Chytridiomycota / Q000502:physiology*; D017377:Diatoms / Q000382:microbiology / Q000502:physiology*; D006790:Host-Parasite Interactions / Q000502:physiology*; D010271:Parasites / Q000382:microbiology*; D010839:Phytoplankton / Q000382:microbiology / Q000502:physiology; D013312:Stress, Physiological / Q000502:physiology*
keywords: aldehydes; amino acids; carbohydrates; chemotaxis; chytrids; fatty acids; parasite-host interactions; phytochemicals; polyunsaturated fatty acids; stress physiology; zoospores