sp . nov . , and other pillotinaceous spirochetes from insects

Pillotinaceous spirochetes (Gram-negative, helical, motile eubacteria greater than 0.4 μm in diameter that are symbionts of metazoa) are known only as normal intestinal microbiota of dictyopterid insects (i.e., xylophagous cockroaches and termites). Because their large diameters imply they contain more than 4–5 periplasmic flagella, observations of live hindgut contents suffice to classify them in the family Pillotinaceae. Further identification requires morphometric analysis of electron microscopic thin sections [14]. The tropical termite Mastotermes darwiniensis (Isoptera; Mastotermitidae), limited today to northern Australia, harbors several amitochondriate anaerobic protists (class Parabasalia) whose rRNA phylogeny is under current investigation [9]. Unlike other extant termites but typical of roaches, the female insect lays egg cases. The extrusion of such structures, comparable to oothecae, leads these modern termites to be classified in the family Mastotermiditidae along with their far more widely spread extinct Eocene, Oligocene and Miocene relatives. A unique wood-digesting microbiota in the hindgut of Mastotermes darwiniensis (the largest termites in Darwin, Australia) was reported by Sutherland [19]. She named Mixotricha paradoxa (“mixed-up hairs paradoxical”) an abundant large uninucleate trichomonad protist that swims forward in a straight line. First suggested to be a ciliate, Mixotricha was claimed by Sutherland to be a unique cell that Andrew Wier Jon Ashen Lynn Margulis