Biology session

The examination that constitutes the subject-matter of my studies came into existence by joining a research team working on the phylogenetics and taxonomy of adeno- and herpesviruses. The family of adenoviruses (Adenoviridae) is widely distributed among vertebrates. Detection of its members before the spread of molecular techniques used to be confined to isolation, serology and electron microscopic studies. By the development of modern diagnostic methods, it has now become possible to detect viral presence directly from the samples of the animals. However, these examinations are still aimed at livestock of agricultural importance, mostly mammals. By the extension of the research field it turned out that in fact every vertebrate class, including reptiles, may harbour adenoviruses. Most types of adenovirus have narrow host spectra, that is each animal species may have its own adenovirus, therefore these viruses are perfectly suitable for investigating co-evolution. In accordance with the earlier results of the research team, out of the presently approved four genera, the genus Atadenovirus represents the lineage of adenoviruses that presumably co-evolved with reptiles, albeit atadenoviruses were originally found in ruminants and birds. Based on whole genome analysis and phylogenetic calculations, an isolate from a snake previously proved to belong to the atadenoviruses. Moreover, the analysis of several lizard and snake samples by PCR likewise pointed towards atadenoviruses. The aim of my study was to uncover further evidence concerning the reptilian origin of atadenoviruses. The bulk of the samples I analyzed came from animals died in pet stores. DNA extracted from the intestines was screened by nested PCR, which amplifies a 300 bp long fragment of the viral DNA polymerase gene. Fragments from the positive samples were sequenced and subjected to phylogenetic tree reconstruction. Sequences from samples of the same host species were compared in order to examine the intraspecific variability of the virus. I analyzed 12 samples of eight reptiles so far coming from the following species: two specimens of Veiled chameleon (Chamaeleo calyptratus), one Pygmy leaf chameleon (Rampholeon brevicaudatus), two Bearded dragons (Pogona vitticeps), two Ground agamas (Agama aculeata), one Savannah monitor (Varanus exanthematicus), one Red-tailed boa (Boa constrictor), two Corn snakes (Elaphe guttata), and one African helmeted turtle (Pelomedusa subrufa). As few as three of the twelve samples proved to be positive during the PCR screening. The virus found in the Bearded dragon proved to be identical to the adenovirus previously detected in the same species in the USA, Germany and Austria. A so far undescribed sequence has also been successfully derived from the Savannah monitor. On the basis of phylogenetic tree reconstruction all three viruses can be assigned to the genus Atadenovirus. Further plans include investigating the genome of the supposedly new atadenovirus found in the monitor.