Expanding Metabolic Diversity of Two Archaeal Phyla: Nanoarchaeota and Korarchaeota

Culture independent studies have revealed a greater diversity of Archaea than the two kingdoms initially defined by Carl Woese. Culturing species from the newly discovered archaeal lineages, as with the majority of microbes, has been difficult. To overcome the culturing dilemma, metagenomics is being used to reconstruct environmental genomes. Two metagenomic studies are presented in this thesis, with the aim of recovering newly proposed archaeal genomes from the Nanoarchaeota and Korarchaeota. In the first study, a sediment sample, NZ13, was collected from a terrestrial New Zealand hot spring. Along with the sediment sample, two complex enrichments were sequenced on an Illumina MiSeq platform. Assembly and differential binning recovered two nearly complete genomes of a nanoarchaeote and a korarchaeote. The NZ13 nanoarchaeote is similar to other terrestrial nanoarchaeotes, which lack an ATP synthase and encode genes for glycolysis/gluconeogenesis and archaella. One notable difference is the NZ13 nanoarchaeote contains CRISPR genes, which are absent in other terrestrial nanoarchaeotes, although present in a marine nanoarchaeote, Nanoarchaeum equitans. The NZ13 korarchaeote mirrors Candidatus Korarchaeum cryptofilum, lacking genes for de novo synthesis of purines and several cofactors, while containing an abundance of peptide transporters and amino acid fermentation pathways. The second study focused on sulfide samples collected from deep-sea hydrothermal vent fields in southwestern Pacific Ocean along the Eastern Lau Spreading Center. Ten sulfide samples were sequenced on an Illumina HiSeq platform. Small subunit ribosomal RNA genes were extracted from the metagenome reads and aligned against the SILVA Ref NR 99 123 database. The preliminary results identified which samples could be prioritized for genome reconstruction of uncultured bacterial and archaeal lineages. Three uncultured bacteria, candidate division SR1, Gracilibacteria (GN02), and Parcubacteria (OD1) were identified in several samples. Many uncultured deep-sea hydrothermal archaeal lineages were identified in all samples. In particular, korarchaeotal sequences were in high relative archaeal abundances in two samples, ABE 1 and Vai Lili-2, while few nanoarchaeotal reads were classified.