Arheje Asgard najbliži prokariotski srodnici eukariota

undergraduate thesis

• Title (english): Asgard archaea the closest prokaryotic relatives of eukaryotes
• Author: Dunja Kureljak
• Mentor: Biljana Balen (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2019, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Asgard arheje nastanjuju raznolika staništa najčešće anoksičnih uvjeta kao što su hidrotermalni
izvori te sedimentni morski i slatkovodni ok oliši. U takvim okolišnim uvjetima česte su mikrobne
interakcije koje su uočene i kod ove skupine, ali još nisu detaljnije istražene. Metabolizam Asgard
arheja veoma je raznolik. Određena koljena sposobna su razgrađivati masne i druge organske
kiseline, pr oteine i ugljikohidrate. Ovi organizmi često su fermentativni te tako ovisno o koljenu
produciraju acetat, laktat ili etanol. Također, jednim od dvaju tipova Wood Ljungdahl (WL) puta
reduciraju CO 2, dok su u nekih koljena zabilježena oba tipa. Posljednje o tkriveno koljeno
Helarchaeota specifično je jer kodira za metil CoM enzime slične reduktazi (Mcr) te stoga ima
potencijal za oksidaciju uglji kohidrata. U nekih koljena nađen je kompletan set gena za protein
RuBisCo tip III i IV te su identificirani novi pi gmenti koje sadrže ove arheje heliorodopsin i
schizorodopsin. Mogu sudjelovati i u kruženju dušika i sumpora. Većina ih je obligatno anaerobna,
dok linija Heimdallarchei a ima potencijal fakultativno aerobnog metabolizma. U genomu Asgard
arheja nađeno je mnogo proteina ESP s za koje se smatralo da postoje samo u eukariota.
Najznačajniji su oni za citoskelet, primjerice homolozi aktina, tubulina i profilina te oni za
membranski transportni sustav, primjerice male GTP aze i komponente vezikularnih omotača.
N apredak u sekvenciranju molekule DNA te razvitak metagenomskih metoda pružaju podatke o
novim arhealnim linijama. Novije filogenetske analize smještaju euk ariote unutar Asgard arheja, s
koljenom Heimdallarchaeota kao najbližim eukariotskim srodnikom. Sve n avedeno pomaže
razumijevanju eukariogeneze i postavljanju novih modela ovog ključnog evolucijskog događaja.

Abstract (english)

Asgard archaea have been found in a diverse range of habitats, primarily in anoxic conditions,
including hydrothermal vents, marine an d freshwater sediments. These conditions support microbial
interactions that are also observed in Asgard superphylum but so far are unexplained. Metabolism
of Asgard archeae is very versatile. Some phyla are capable of degradation of fatty and other
organi c acids, proteins and carbohydrates. These organisms often ferment so that they can produce
acetate, lactate or ethanol. Moreover, they reduce CO 2 via one of two Wood Ljungdahl (WL)
pathways, while some use both of the m. The latest discovered phylum Helarc haeota has specific
metabolism because it encodes for methyl CoM reductase like enzymes (Mcr) so it has potential for
hydrocarbon oxidation. Some phyla were found to harbor complete set of genes for RuBisCo types
III and IV. Recently, new Asgard archea pig ments are identified heliorhodopsin and
schizorhodopsin. Some of the archea are also involved in nitrogen and sulfur cycling. Most of them
are obligately anaerobic, while archaeal lineage Heimdallarchaeia has potentially facultative aerobic
metabolism. A sgard archaea genome encoded for numerous eukaryotic signature proteins (ESPs)
that were previously considered to be eukaryotic specific. The most significant ESPs are for
cytoskeleton, such as actin, tubulin a nd profilin homologues and ESPs for membrane t rafficking
system such as small GTPases and vesicle coat components. Developed DNA sequencing
technologies and me tagenomic approaches provide us datasets about new archaeal lineages. New
phylogenetic analysis place eukaryotes within the Asgard superphylum, more closely related to the
phyllum Heimdalla rchaeota. All these discoveries help in understanding of eukaryogenesis and
proposing new models for this key evolutionary event.

• Keywords: arheje Asgard
• Language: croatian
• URN:NBN: urn:nbn:hr:217:576367
• Study programme: Title: Ecology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-09-26 07:42:12