Symbiotic Relationship of Thiothrix spp. with an Echinoderm

ABSTRACT

Immunoassay procedures were used to investigate the symbiotic relationship of Thiothrix spp. in the intestinal cecum of the spatangoid species Echinocardium cordatum. Thiothrixspp. were identified in nodule samples from E. cordatum digestive tubes based on microscopic examination, enzyme-linked immunosorbent assay, and indirect immunofluorescence.Thiothrix spp. protein made up as much as 84% of the total protein content of the nodules. This is the first identification ofThiothrix spp. internally symbiotic with marine invertebrates.