No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Evaluation of Experimental Design Options in Environmental Nano-Science Research As an experimental research design plays a pivotal role in executing a research problem, it is imperative of a researcher to develop a suitable and sound research design. Utilizing robust statistical methods can further enhance the study power and thus allow drawing a logical conclusion. The same holds true for basic environmental science research, including research related to the effects of engineered nanomaterials in the environment.

Since the Industrial Revolution at the end of the 18th century, anthropogenic changes in the environment have shifted from the local to the global scale. Even remote environments such as the high Arctic are vulnerable to the effects of climate change. Similarly, anthropogenic mercury (Hg) has had a global reach because of atmospheric transport and deposition far from emission point sources. Whereas some effects of climate change are visible through melting permafrost, or toxic effects of Hg at higher trophic levels, the often-invisible changes in microbial community structures and functions have received much less attention. With recent and drastic warming-related changes in Arctic watersheds, previously uncharacterized phylogenetic and functional diversity in the sediment communities might be lost forever. The main objectives of my thesis were to uncover how microbial community structure, functional potential and the evolution of mercury specific functions in lake sediments in northern latitudes (>54ºN) are affected by increasing temperatures and Hg deposition. To address these questions, I examined environmental DNA from sediment core samples and high-throughput sequencing to reconstruct the community composition, functional potential, and evolutionary responses to historical Hg loading. In my thesis I show that the microbial community in Lake Hazen (NU, Canada) sediments is structured by redox gradients and pH. Furthermore, the microbes in this phylogenetically diverse community contain genomic features which might represent adaptations to the cold and oligotrophic conditions. Finally, historical Hg pollution from anthropogenic sources has likely affected the evolution of microbial Hg resistance and this deposition can be tracked using sediment DNA on the Northern Hemisphere. My thesis underscores the importance of using culture-independent methods to reconstruct the structure, functional potential and evolution of environmental microbial communities.

Aigarchaeota, a deeply branching archaeal lineage with no cultivated representatives, is found in geothermal and hydrothermal systems worldwide and consists of at least 9 genus-level groups, each predicted to have diverse metabolic capabilities. This candidate archaeal phylum is part of the TACK superphylum, members of which possess eukaryotic-signature proteins, thus suggesting that they may represent evolutionary steps along the way to the genesis of the first eukaryotic cells. Cultivating members of Aigarchaeota would elucidate how eukaryotes arose in evolutionary history and provide biotechnological applications. Aigarchaeota Group 4 (AigG4), one genus in Aigarchaeota, was previously found to be abundant in corn stover in situ enrichments in Great Boiling Spring (GBS). AigG4 has been maintained in mixed laboratory cultures, where it composes ~ 0.5-1% of the community. However, these cultures could only be maintained when GBS water, which contains ~300 nM tungsten, was included in the medium. In addition, AigG4 metagenome bins from the in situ enrichments and laboratory cultures contained multiple genes encoding putative tungsten-containing aldehyde:ferredoxin oxidoreductases (TAORs). These observations led to the hypothesis that tungsten was the key component in GBS water that allowed for growth of AigG4. The requirement of tungsten for AigG4 long-term maintenance in mixed culture was tested using three different approaches: (1) Assessing the phylogeny of tungsten transporters and TAORs across the Aigarchaeota lineage, followed by confirmation of transcription of hypothesized AigG4 tungsten-associated genes in lab cultures, (2) Measuring tungsten levels in Great Boiling Spring (GBS) using ICP-OES (Inductively coupled plasma-optical emission spectroscopy), and (3) determining minimum amount of tungsten for long-term AigG4 maintenance in corn stover and in a defined mix of sugars (1% glucose, 1% xylose, 1% D-arabinose, 1% L-arabinose, 1% mannose). In addition, FISH (Fluorescent in situ hybridization) probes were designed to target the AigG4 lineage in the hopes that in conjunction with nanometer-scale secondary ion mass spectroscopy (Nano-SIMS), this would test whether tungsten has indirect or direct effects on AigG4 to track carbon substrate intake. Most Aigarchaeota lineages possess a tungsten transporter complex (TTC). AigG4 TTC groups most closely with the Tup family while other Aigarchaeota group with the Wtp family. Group 4 and Group 5 Aigarchaeota contained TAORs that grouped to other hypothesized TAORs but not to characterized counterparts suggesting diverse functional capabilities. Group 4 and Group 5 TAORs clustered together suggesting that these are conserved within these lineages. Gene expression of predicted AigG4 tungsten-associated enzymes was detected in culture. Tungsten was detected in GBS water as previously observed in 2005. In both corn stover and sugar mix, 1 nM tungsten was sufficient for long term AigG4 maintenance. In corn stover, AigG4 decreased to levels below detection after three 3-week transfer periods in 0 nM and 20 nM tungsten. In sugar mix, AigG4 abundance levels varied wildly in 0 nM tungsten after the fifth transfer period suggesting tungsten contamination. Two newly designed FISH probes exhibited lower fluorescence signal intensity than the previously designed FISH probe suggesting issues with either target site accessibility or conjugation of the fluorescent moiety to oligonucleotide probes.