Canaleparolina darwiniensis, gen. nov., sp. nov., and other pillotinaceous spirochetes from insects.

Abstract

We describe two new pillotinaceous spirochetes (Canaleparolina darwiniensis, Diplocalyx cryptotermitidis) and identify for the first time Hollandina pterotermitidis from both the subterranean termite Cryptotermes cavifrons and the wood-eating cockroach Cryptocercus punctulatus based on morphometric analysis of transmission electron micrographic thin sections. C. darwiniensis, gen. nov., sp. nov., limited to near Darwin, Australia, invariably is present on the surface of the treponeme-studded trichomonad Mixotricha paradoxa, a consistent inhabitant of the hindgut of healthy termite Mastotermes darwiniensis. The spirochete both attached to the surface of protists and free-swimming in the paunch (hindgut) lumen of the insect has 16 periplasmic flagella (16:32:16) and imbricated wall structures that resemble flattened crenulations of Pillotina. The flagella surround half the protoplasmic cylinder. C. darwiniensis is the largest (0.5 microm diameter x 25 microm length) of the three epibiotic bacteria (two spirochetes, one rod) that comprise the complex cortex of its host Mixotricha paradoxa. Several criteria distinguish Diplocalyx cryptotermitidis sp. nov. isolated from Cryptotermes cavifrons intestine: smaller diameter, fewer flagella, absence of inner and outer coats of the outer membrane, wider angle subtended by its flagella and, most notably, cytoplasmic tubule-associated centers, which are periodic electron dense spheres within the protoplasmic cylinder from which emanate cytoplasmic tubules up to 24 nm in diameter. This is also the first report of abundant populations of Hollandina in Cryptotermes cavifrons (those populations belong to the species H. pterotermitidis). Morphometric analysis of the first thin sections of any spirochetes (published nearly 40 years ago by A.V. Grimstone) permits us to identify the large (0.9 microm diameter) free-swimming intestinal symbiont of Cryptocercus punctulatus also as Hollandina pterotermitidis.