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Genome evolution of endosymbiotic bacteria in blood-sucking insects
ŘÍHOVÁ, Jana
The research on insect-bacteria symbiosis is experiencing a rapid burst leading to the identification of much higher complexity and dynamics of the insect-bacteria associations than ever before envisaged. The generally accepted concept of obligate bacterial symbionts as providers of essential compounds (vitamins, aminoacids) has been further developed into the framework of microbiomes, i.e. communities of microorganisms associated with the host. The majority of the knowledge has been derived from plant sap-feeders, while data on blood-feeding insects remain fragmented and even inconsistent. In this thesis, we employ amplicon, genomic and in-vivo approaches to investigate several symbiotic systems of obligate blood-feeders and address the following questions: What is the diversity of symbiotic bacteria in our studied systems? What are the metabolic capacities of these symbionts? What is the role of symbionts in the biology of their hosts? What are the possible sources of bacteria prone to establish symbiosis with obligate blood-feeders? Where these symbionts reside in the host´s body? What is the coevolutionary pattern of these bacteria with their hosts? As an answer to these questions, I present the results detailed in the course of this thesis, which are preceded by a comprehensive introduction to the studied topics and wraps up with a summary of the main results.
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Phylogenetic Position of Genus Polymastix and Its Prokaryotic Symbionts
Kubánková, Aneta ; Hampl, Vladimír (advisor) ; Kolísko, Martin (referee)
Polymastigidae is one of the five families of oxymonads (Metamonada, Preaxostyla). It includes small flagellates inhabiting the digestive tract of insects. Recently obtained molecular phylogenetic data have questioned the monophyly of this group. The type genus of the family Polymastigidae is Polymastix. The phylogenetic position of this genus has not been studied yet, although this information could significantly help to clarify the relationships within this group. This work provides the first sequence data of this genus, which we have obtained using a single- cell genome amplification and subsequent whole genome sequencing on Illumina HiSeq X Ten (Macrogene) from three individuals of P. melolonthae inhabiting the posterior hindgut of crane fly larvae. Phylogenetic analysis based on the gene for 18S rRNA, EF-1α and HSP90 yielded several roughly equally probable hypotheses about the position of this genus within Oxymonadida. The first of them places the genus Polymastix in a close proximity to the genus Streblomastix, according to the second hypothesis, Polymastix is sister to Termitimonas travisae. A characteristic feature of this protist is ectosymbiotic bacteria attached to its surface. These were necessarily amplified and sequenced together with their hosts, which allowed us to obtain sequence...
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Multilokusová charakteristika symbiontů entomopatogenních hlístovek rodu \kur{Steinernema}
FAKTOROVÁ, Lucie
During the evolution some groups of organisms have become coevolutionary associated with other groups, as is the case of host symbiont systems. To explore coevolutionary history of hosts and their associated symbionts, phylogenetic reconstruction of symbionts and phylogenetic reconstruction of hosts are usually compared. Coevolution is described by coevolutionary events (cospeciation, host switch, duplication, failure to diverge events and linage sorting events). The aim of this work was to test the suitability of MLST method for the complex of entomopathogenic nematodes from the genus Steinernema (with detailed analysis of Steinernema feltiae) and their symbiotic bacteria Xenorhabdus bovienii and subsequently use cophylogenetic comparative analysis to determine their level of cospeciation.
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Molecular phylogeny and genome evolution of insect symbiotic bacteria
NOVÁKOVÁ, Eva
Since the introduction of advanced molecular methods the research on insect bacterial symbioses underwent a major focus shift towards large scale phylogenetics and comparative genomics. These new fields provided answers to several fundamental questions of symbiont evolution, functional capabilities of the host-associated bacteria, and the role of symbionts in the host?s biology. However, the vast diversity and complexity of symbiotic relationships still leaves gaps in our understanding to a rich mosaic of various symbiont types, effects and transitions from facultative association to obligate mutualism. The presented study focuses on distribution, diversity, phylogenetic patterns, evolutionary transitions and genome evolution of two less known but ecologically diverse bacterial genera, Arsenophonus and Sodalis. The thesis also takes advantage of the knowledge on a well established symbiotic model between aphids and Buchnera and reveals several evolutionary patterns in the host and symbiont.
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