Editors' ChoiceEcology

Hostile Interactions in the Middle East

Science's STKE  22 Oct 2002:
Vol. 2002, Issue 155, pp. tw379-TW379
DOI: 10.1126/stke.2002.155.tw379

Phytoplankton, microscopic plants that inhabit aquatic ecosystems, are the first link in the aquatic food chain and can influence climate globally by altering amounts of atmospheric carbon dioxide. Certain species produce toxins that can impact human health. In the Sea of Galilee, Peridinium gatunense, a dinoflagellate that forms large, dense patches, has historically dominated the phytoplankton community. Over the past decade, however, annual blooms of P. gatunense have been delayed or absent. Vardi et al. investigated interactions between P. gatunense and Microcystis, a toxic cyanobacterium, and discovered that substances released into the water by one or the other of these microorganisms influenced survival of the other through species-specific signal transduction pathways. Statistical analyses indicated a negative correlation between abundance of the two microorganisms in the wild, and long-term growth experiments showed reciprocal inhibition of growth between P. gatunense and Microcystis that depended on the initial density of P. gatunense but was independent of nutrient supply. A particular species, Microcystis MG, triggered a biphasic oxidative burst in P. gatunense and promoted cell death under some culture conditions while stimulating division of surviving cells. Pharmacological analysis with protein kinase inhibitors, together with in-gel kinase and Western blot analysis, implicated mitogen-activated protein kinase pathways in the P. gatunense response. Medium from cultures of P. gatunense triggered massive Microcystis MG lysis, but increased amounts of a protein involved in toxin biosynthesis in the remaining cells. The authors suggest that phytoplankton can influence the growth of other species through interactions with specific signal transduction pathways; such interactions raise the possibility of biological control of toxic species.

A Vardi, D Schatz, K Beeri, U Motro, A Sukenik, A Levine, A Kaplan, Dinoflagellate-cyanobacterium communication may determine the composition of phytoplankton assemblage in a mesotrophic lake. Curr. Biol. 12, 1767-1772 (2002). [Online Journal]