Faculty of Natural
Comenius University in Bratislava

Peter Vdacny Lab

Our lab is driven by passion for understanding biological evolution and formation of diversity during the geological history of Earth. We are focused on ciliates, widespread microbial eukaryotes. During the more than one billion year long evolutionary history, ciliates have become one of the most diverse group of unicellular eukaryotes, accounting for about 8,000 described species. They are either free-living or they have entered into diverse associations with many animal hosts. About one third of extant ciliates are thus symbionts, most of them are harmless commensals, but some may be pathogenic and cause severe damage to their hosts.



Currently we attempt to solve three problems in evolutionary history of ciliates:

  1. Phylogenetic interrelationships among free-living, predatory litostomatean ciliates
  2. Diversity and evolution of hindgut ciliates from wood-feeding cockroaches and their associations with prokaryotes
  3. Evolution of the ciliate/invertebrate symbiotic systems

1. Phylogenetic interrelationships among free-living litostomatean ciliates

The class Litostomatea represents a monophyletic group, comprising both predatory and endosymbiotic ciliates distributed all over the globe. At first glance, litostomateans are rather simple, uniformly ciliated protists having bursiform bodies. Their oral structures are very diverse, a fact that was used in their morphology-based taxonomy during the ultrastructure era. In the recent decades, the systematic research on litostomateans has concentrated mainly on the ribosomal RNA genes and ITS-region sequences. Phylogenetic relationships among main free-living litostomatean lineages are still unresolved, however. We search for evolutionary forces and investigate problems that might be associated with the puzzling picture in litostomatean phylogenies. We also examine the utility and phylogenetic information content of ribosomal and protein-coding genes in free-living litostomateans.

2. Diversity and evolution of hindgut ciliates from wood-feeding cockroaches and their associations with prokaryotes

The ability to digest wood evolved two times independently in the insect order Blattodea. First, in the common ancestor of termites and cryptocercids, and then in the panesthiine cockroaches. The hindgut compartment of panesthiines harbors a diverse, anaerobic microbial community, including also three closely related ciliate genera Clevelandella, Paraclevelandia, and Nyctotherus. These ciliates are, however, not associated with the digestion of wood but contribute to the overall hindgut function by their grazing behavior, which helps to shape and regulate prokaryotic populations. We investigate co-occurrence and correlation patterns of prokaryotes associated with these hindgut ciliates. We also study speciation, species borders, and mechanisms that have led to diversification of the hindgut ciliates.

3. Evolution of the ciliate/invertebrate symbiotic systems

Many animals have established associations with some epi- and/or endozoic ciliates. The free-living flatworms and terrestrial annelids do not represent an exception. However, the diversity of these symbiotic systems is far from being thoroughly examined. Present phylogenetic studies suggest that divergences of endosymbiotic ciliates are related to those of higher taxa of their hosts. Our main goal is to address the following questions:

  • How many times have ciliates entered into associations with freshwater tricladid flatworms and terrestrial oligochaetes?
  • Are various groups of endosymbiotic ciliates more closely related to free-living or to other symbiotic ciliates?
  • Does the position of symbiotic ciliates in phylogenetic trees copy occurrence of their hosts in the geological history of Earth?


Current Lab members

Peter Vďačný

Ľubomír Rajter

PhD Candidate
Research Interest: My research interest is in the field of systematics and taxonomy of predatory ciliates of the class Litostomatea. In my studies, I apply a combination of molecular and morphological techniques along with a complex statistic approach. I am trying to understand and decipher the litostomatean evolutionary history, what represents an amazing scientific journey for me.
E-mail: lubomir.rajtergmail.com

Rajter Ľ., Vďačný P. (2016): Rapid radiation, gradual extinction and parallel evolution challenge generic classification of spathidiid ciliates (Protista, Ciliophora). Zoologica Scripta 45 (2), 200-223.

Rajter Ľ., Vďačný P. (2017): Constraints on phylogenetic interrelationships among four free-living litostomatean lineages inferred from 18S rRNA gene-ITS region sequences and secondary structure of the ITS2 molecule. Acta Protozoologica 56 (4), 255-281.

Rajter Ľ., Vďačný P. (2018): Selection and paucity of phylogenetic signal challenge the utility of alpha-tubulin in reconstruction of evolutionary history of free-living litostomateans (Protista, Ciliophora). Molecular Phylogenetics and Evolution 127, 534-544.

Vďačný P., Rajter Ľ. (2014): An annotated and revised checklist of pleurostome ciliates (Protista: Ciliophora: Litostomatea) from Slovakia, Central Europe. Zootaxa 3760 (4), 501-521.

Vďačný P., Rajter Ľ. (2015): Reconciling morphological and molecular classification of predatory ciliates: Evolutionary taxonomy of dileptids (Ciliophora, Litostomatea, Rhynchostomatia). Molecular Phylogenetics and Evolution 90, 112–128.

Vďačný P., Rajter Ľ., Shazib S.U.A., Jang S.W., Kim J.H., Shin M.K. (2015): Reconstruction of evolutionary history of pleurostomatid ciliates (Ciliophora, Litostomatea, Haptoria): interplay of morphology and molecules. Acta Protozoologica 54 (1), 9-29.

Vďačný P., Rajter Ľ., Shazib S.U.A., Jang S.W., Shin M.K. (2017): Diversification dynamics of rhynchostomatian ciliates: the impact of seven intrinsic traits on speciation and extinction in a microbial group. Scientific Reports 7 (1), 9918.

Matej Rataj

PhD Candidate
Research Interest: My research interest is in endosymbiotic ciliates, with a focus on a relatively poorly explored group of astome ciliates. I find them attractive through their life strategy encompassing different types of host species. Most I like on this work is making visible organisms that are most of the time hidden from our sight.
E-mail: matej.ratajgmail.com

Rataj M., Vďačný P. (2018): Dawn of astome ciliates in light of morphology and time-calibrated phylogeny of Haptophrya planariarum, an obligate endosymbiont of freshwater turbellarians. European Journal of Protistology 64, 54-71.

Rataj M., Vďačný P. (2019): Living morphology and molecular phylogeny of oligohymenophorean ciliates associated with freshwater turbellarians. Diseases of Aquatic Organisms 134 (2), 147-166.

Vďačný P., Rataj M. (2017): Evaluation of systematic position of helicoprorodontids and chaeneids (Ciliophora, Litostomatea): An attempt to break long branches in 18S rRNA gene phylogenies. Journal of Eukaryotic Microbiology 64 (5), 608-621.

Tomáš Obert

Undergraduate Researcher
Research Interest: My research is focused on diversity and morphological as well as genetic variability of intestinal endosymbionts of earthworms in the surroundings of the capital city of Slovakia. 
E-mail: tomasobert.obertgmail.com

Lukáš Pecina

Undergraduate Researcher
Research Interest: My research interests are focused on cockroaches and microbial communities associated with their digestive tract. Specifically, I study evolution and distribution of endosymbiotic ciliates from the family Clevelandellidae, living in the wood-feeding cockroaches of the genus Panesthia. Phylogenetic relationships within the family Clevelandellidae also have come to my attention.
E-mail: pecinalukas1gmail.com

Vďačný P., Érseková E., Šoltys K., Budiš J., Pecina L., Rurik I. (2018): Co-existence of multiple bacterivorous clevelandellid ciliate species in hindgut of wood-feeding cockroaches in light of their prokaryotic consortium. Scientific Reports 8, 17749.

Past Lab members

Michaela Bohatová

Diploma Thesis: Locomotory behaviour of Coleps hirtus and Spathidium muscicola (Protista: Ciliophora).

Bohatová M., Vďačný P. (2018): Locomotory behaviour of two phylogenetically distant predatory ciliates: does evolutionary history matter? Ethology Ecology & Evolution 30 (3), 195-219.

Emese Érseková

Diploma Thesis: Diversity and association of prokaryotes with ciliates of the order Clevelandellida (Ciliophora: Armophorea)

Vďačný P., Érseková E., Šoltys K., Budiš J., Pecina L., Rurik I. (2018): Co-existence of multiple bacterivorous clevelandellid ciliate species in hindgut of wood-feeding cockroaches in light of their prokaryotic consortium. Scientific Reports 8, 17749.