Meeting Abstract

P2.223  Saturday, Jan. 5  Symbiodinium mucilage and ultrastructural variation MAZZILLO MAYS, M.*; KEMPF, S. C.; Auburn University; Auburn University mazzimj@auburn.edu

Symbiodinium are unicellular dinoflagellates that reside intracellularly in a variety of invertebrate hosts, including cnidarians. In this symbiosis, the endosymbiotic algae are enclosed in a symbiosome membrane (host and symbiont-derived) and donate photosynthetically fixed carbon to the host in exchange for nutrients. Symbiodinium is a diverse genus of 9 clades with multiple strains in each clade. The specificity of the association between symbiont and host varies with some relationships being highly specific and others of a general nature. The symbiont secretes mucilage that lies at the interface with the host and therefore, may be involved in recognition and specificity. Antigenic variation of this mucilage layer demonstrated that differences are present in the mucilage layer that could impact recognition and specificity. An antigen previously created against a clade B alga from Aiptasia pallida was found in cultured Symbiodinium from clades A and B but not clades C, D, and F. Within clades A and B there was variation in the amount of label present. Ultrastructural examinations using High Pressure Rapid Freezing were then performed on 6 strains (2 each from clades A and B, 1 from clade C, and a free-living Symbiodinium strain from clade E) to examine variation amongst these strains that could effect the ability of a particular symbiont to reside within a particular host. Variations in mucilage composition could provide important molecular differences involved in the recognition of a symbiont by the host. Examining the ultrastructure of the symbiont may help to explain where variation between strains may exist, and how this variation may impact both the recognition and establishment of a symbiosis as well as its maintenance.