Light microscopic morphometrics, ultrastructure, and molecular phylogeny of the putative pycnotrichid Ciliate, Buxtonella sulcata

• First detailed report of the morphology, ultrastructure and genetics of B. sulcata.
• Cytoplasm containing endosymbiotic bacteria and possible pynocitotic vesicles.
• There exist genetic variants identified by ITS sequence-structure analysis.
• Phylogenetic position unclear but related to Balantidiidae and Pycnotrichidae.

The ciliate, Buxtonella sulcata, was isolated from a bull cow near Tišnov, Czech Republic, and fixed for light (LM), scanning electron (SEM) and transmission electron microscopic (TEM) study. Presented here are the basic morphometrics from LM study, and the fine-structure of both somatic and vestibular ciliary, and other structures. While many morphological features are similar to ciliates belonging to the order Vestibuliferida, some differences have been discovered, and are presented here. Especially emphasized are the microtubular and fibrilar components of the basic kinetid structures for both somatic and vestibular regions of these protists. Also observed in both TEM and SEM samples were enigmatic membrane bulges at the base of many somatic cilia. These ciliates are seen to have abundant endocytoplasmic bacteria, as seen in LM and TEM. This evaluation of the ultrastructural morphology of B. sulcata from cattle is accompanied by detailed determination of its small subunit rRNA (SSU rRNA) gene sequence and also of internal transcribed spacers (ITS1-5.8rRNA-ITS2). All of these data will contribute to unravel the phylogenetic relationships of medically and veterinary important intestinal ciliates.