Adhering epibionts with distinctive attachment structures form surface striations on Staurojoenina, a termite hindgut hypermastigote. These striations, first called cuticle thickenings by Kirby, are always present on Staurojoenina assimilis and are intrinsic to the description of the species in this genus of amitochondriate protists. Studies of the live protist by videomicroscopy, fluorescence light microscopy, scanning and transmission electron microscopy as well as 16S rRNA analysis confirm their identity. Each of the conspicuous, uniformly distributed, surface striations (0.2-0.3 [mu]m x 2.5-7.0 [mu]m) is attached longitudinally by a hook to the protist membrane. They contain nucleoids that fluoresce with SYTOX, a DNA stain. The striations are rod-shaped, gram-negative enterobacteriaceae. Phylogenetic analysis using the 16S rRNA genes show that the epibionts can be placed firmly within the Citrobacter clade. Although they have not been isolated and grown in culture we argue that enough morphological, ecological and molecular biological information about these surface symbionts of Stattrojoenina assimilis exist for them to merit identification by name. Accordingly we formally describe the epibionts as Candidatus Cuticobacterium kirbyi. These specimens were taken from a newly discovered source of Staurojoenina assimilis from two Caribbean islands
