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Research Area

Research projects: "Chemical ecology of cross-kingdom interactions"

The focus of our research group is to elucidate the mutualistic interactions between prokaryotes and eukaryotes ("cross-kingdom cross-talk"). Our previous work has shown that challenges of chemical ecology - at the interface between biology and chemistry - can only be resolved successfully by an interdisciplinary research approach. The consistent combination of classical bioassays and chemical analytical methods reveals novel insights into the complex networks of infochemicals and signal molecules along with their ecophysiological significance. Our research approach focuses on the fundamental understanding of the functioning of infochemicals in biocoenoses that can be mimicked in laboratory studies after which field experiments are conducted to prove their ecological significance.

To reach this goal, two major research initiatives have been established:

I. Studies of the symbiotic interactions between bacteria and marine macroalgae

- To decipher the chemosphere of the marine green algae Ulva sp. and its associated bacteria.

- To understand the cross kingdom talk of bacteria and Ulva sp. based on infochemicals.

II. Studies of metal-recruitment by nitrogen-fixers

- To identify metallophores for the metal uptake by these bacteria.

- To measure the bioavailability of trace metals essential for the nitrogenase.



Symbiotic interactions of the marine macroalgae Ulva mutabilis and its associated bacteria

Tripartite community

Tripartite community and representative morphotypes. Tripartite community of U. mutabilis with proposed essential interactions for standardized experimental set-ups. A combination of Roseobacter sp. (MS2) and Cytophaga sp. (MS6) excreting morphogenetic substances recover growth and morphogenesis of the wildtype (shown in the top) and the mutant slender of U. mutabilis: Roseobacter sp. promotes cell division (A: scale bars = 1 mm) and Cytophaga sp. promotes rhizoid and cell wall formation (B: scale bars = 1 mm). Strictly axenic cultures develop into a callus like morphotype consisting of undifferentiated cells without normal cell walls. Image: © Wichard T (2015) Exploring bacteria-induced growth and morphogenesis in the green macroalga order Ulvales (Chlorophyta). Front. Plant Sci. 6:86. doi: 10.3389/fpls.2015.00086. This project is funded by the Colaborative Research Center "Chemical Mediators In Complex Biosystems" ChemBioSys SFB 1127 - Project A01.



Regulation of gametogenesis and gamete release of Ulva sp.

Gametogenesis

Induction and regulation of gametogenesis and zoosporogenesis in Ulva mutabilis and Ulva linza. Phenotypic changes of blade cells during gametogenesis and gamete release. (A) Blade cells 24 h after induction resemble uninduced blade cells: cells are square and often in transverse rows. (B) 48 h after induction, blade cells differentiate into gametangia containing finally 16 progametes, which mature during the following night into fully developed gametes ready for swarming. (C,D) Gametes are discharged in the morning of the third day. (E) Discharged sporangia and (F) zoospores within a sporangium are shown. Gametophytes (A-D) and sporophytes (E,F) were grown under standard conditions (Scale bars: A,B,D = 25 μm; C = 140 μm, E = 16 μm, F = 4 μm). Image: © Vesty EF, Kessler RW, Wichard T and Coates JC (2015) Regulation of gametogenesis and zoosporogenesis in Ulva linza (Chlorophyta): comparison with Ulva mutabilis and potential for laboratory culture. Front. Plant Sci. 6:15. doi: 10.3389/fpls.2015.00015.



Metallophores as mediators for metal cycling

Wichard Frankia

A) The tripartite system is facilitated by an effective metal recruitment by the Frankia spp. and mycorrhiza. B) Uptake of essential trace metal by the nitrogen fixation Frankia sp. in growth medium. Isotopes labeled compounds (red) are supposed to be identified (metallophores) or synthesized (ligands) within this project. This project is funded by the Colaborative Research Center "Chemical Mediators In Complex Biosystems" ChemBioSys SFB 1127 - Project C05.


Determination and quantification of metallophores released by nitrogen fixing bacteria

Graphical abstract metallophors

Metal isotope coded profiling (MICP) introduces a universal discovery platform for metal chelating natural products that act as metallophores, ion buffers or sequestering agents. The detection of cation and oxoanion complexing ligands is facilitated by the identification of unique isotopic signatures created by the application of isotopically pure metals. Figure © Deicke, M., Mohr, J. F., Bellenger, J. P., Wichard, T. (2014) Metallophore mapping in complex matrices by metal isotope coded profiling of organic ligands. Analyst, 23, 6096 - 6099.



Signalling in seaweeds: Oxylipin production of Ulva sp.

Graphical abstract oxylipin


Lipoxygenase mediated pathways catalyze the release of 2,4-decadienal and 2,4,7-decatrienal derived from polyunsaturated fatty acids upon wounding. The production of polyunsaturated aldehydes (PUAs) by the green tide forming algae Ulva was surveyed in the lagoon Ria Formosa in Portugal. We are interested in the  the biosynthetic pathways of PUA-production in Ulva spp. The depletion of polyunsaturated fatty acids jeopardizes the amount of economical relevant resources from UlvaChemistry and Physics of Lipids, 183, 100-109.