title: A Fateful Meeting of Two Phytoplankton Species-Chemical vs. Cell-Cell-Interactions in Co-Cultures of the Green Algae Oocystis marsonii and the Cyanobacterium Microcystis aeruginosa.
abstract: Massive growth of single species of cyanobacteria is a common phenomenon in many eutrophicated waters worldwide. Allelopathic growth control of phytoplankton species is one suggested mechanism, but still controversially discussed. The fact that the synthesis of biological active compounds requires high energy costs and carbon investment for a single cell in contrast to high dilution rates in natural systems questions the universal validity of allelopathic mechanisms, even more as high concentrations of allelopathic substances are often needed in several experiments to cause biological effects. In this study, it was tested, if growth inhibition is induced by chemical signaling alone or via direct cell-cell interaction. As a test system, we used a co-culture of the green algae Oocystis marsonii (Trebouxiophyceae) with the cyanobacterium Microcystis aeruginosa which is known to strongly reduce the growth of the green algal competitor. In this study, direct co-culturing as well as membrane-separated growth chambers were used to test for chemical and contact-mediated interactions. In the membrane-separated chambers, both species can be co-cultivated and a membrane allows the exchange of metabolites. Growth of O. marsonii was only affected in the direct co-cultivation situation, where direct cell-to-cell contact was possible. During direct co-cultivation, deviating cellular traits, namely cell cycle pattern and large cell-aggregate formation of both species, could be detected. These data strongly support the hypothesis of a direct cell-cell-contact necessary for allelopathic growth control in this model system. Such direct contact would allow targeting allelopathic metabolites directly towards the competitor and thereby minimizing dilution effects.
authors.affiliation: Centre for Environmental Research - UFZ, Permoserstraße 15, 04318, Leipzig, Germany. susanne.dunker@ufz.de.|German Centre for Integrative Biodiversity Research - iDiv, Deutscher Platz 5a, 04103, Leipzig, Germany. susanne.dunker@ufz.de.
authors.forename: Susanne
authors.identifier: 0000-0001-7276-776X
authors.initials: S
authors.lastname: Dunker
authors.affiliation: Institute of Inorganic and Analytical Chemistry/Bioorganic Analytics, Friedrich Schiller University Jena, 07743, Jena, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Althammer
authors.affiliation: German Centre for Integrative Biodiversity Research - iDiv, Deutscher Platz 5a, 04103, Leipzig, Germany.|Institute of Inorganic and Analytical Chemistry/Bioorganic Analytics, Friedrich Schiller University Jena, 07743, Jena, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Pohnert
authors.affiliation: German Centre for Integrative Biodiversity Research - iDiv, Deutscher Platz 5a, 04103, Leipzig, Germany.|Department of Plant Physiology, University of Leipzig, Johannisallee 23, 04103, Leipzig, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Wilhelm
mesh_terms: D064089:Allelopathy; D000460:Chlorophyta / Q000737:chemistry / Q000502:physiology*; D018920:Coculture Techniques; D046931:Microcystis / Q000737:chemistry / Q000502:physiology*; D010839:Phytoplankton / Q000737:chemistry / Q000502:physiology
keywords: Aggregates; Allelopathy; Cell–cell contact; Co-cultivation; Membrane-separated culture chambers; Microcystin