First Advisor

Anna-Louise Reysenbach

Date of Publication

Winter 3-13-2019

Document Type


Degree Name

Master of Science (M.S.) in Biology






Archaebacteria -- Ecophysiology -- New Zealand, Host-bacteria relationships, Thermophilic bacteria -- New Zealand



Physical Description

1 online resource (ix, 130 pages)


The Nanoarchaeota are an enigmatic lineage of Archaea found in deep-sea hydrothermal vents and geothermal springs across the globe. These small (~100-400 nm) hyperthermophiles live ectosymbiotically with diverse hosts from the Crenarchaeota. Despite their broad distribution in high-temperature environments, very few Nanoarchaeota have been successfully isolated in co-culture with their hosts and nanoarchaeote genomes are poorly represented in public databases. However, the Nanoarchaeota provide unique insights into the structure and function of symbiosis in the archaeal domain. This study describes novel nanoarchaeotes from multiple geothermal habitats, using a combination of direct cultivation techniques and genomic analysis. A new nanoarchaeote from a New Zealand hot spring, Candidatus Nanoclepta minutus, was isolated in co-culture with its host. Like other terrestrial Nanoarchaeota, Cand. Ncl. minutus harbors genes for gluconeogenesis and archaeal flagella. Zestosphaera tikiterensis, the New Zealand host, was also isolated in pure culture and characterized. Phylogenetic analysis showed that both Cand. Ncl. minutus and Z. tikiterensis are new genera in the Nanoarchaeota and Crenarchaeota, respectively. Metagenome-assembled genomes (MAGs) from the Nanoarchaeota were also recovered from deep-sea hydrothermal vent sites. These MAGs capture a wide range of diversity in the Nanoarchaeota, representing three new species and two novel genera. Key nanoarchaeotal features were identified in the MAGs, including marker genes for archaeal flagella, gluconeogenesis and CRISPR-Cas regions. These studies greatly contribute to our understanding of nanoarchaeotal ecophysiology and provide key insights into the coding potential and diversity of Nanoarchaeota and their hosts.


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Supplementary files are available in the Additional Files below

Persistent Identifier

629005_supp_s1.xml (5143 kB)
This file contains tables that correspond to data in Chapter 2, as detailed below. The document is approximately 5 megabytes in size and is saved in the extensible markup language (XML) format. Contents can be viewed in Microsoft Office XML Handler.

629005_supp_s2.xml (408578 kB)
This file holds supplementary tables for Chapter 3, as listed below. The XML file is readable in Microsoft Office XML Handler and is approximately 418 megabytes in size.

629005_supp_s3.txt (70 kB)
Concatenated ribosomal protein alignment used to construct Figure 1.8. This text file is 71 kilobytes in size and can be opened with a text editor.