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UID:20251106T001627EST-1224PFT7vz@132.216.98.100
DTSTAMP:20251106T051627Z
DESCRIPTION:pre-defense will be at 10:00 AM (room MS2-084)  Abstract:  The 
 Lost Hammer (LH) spring\, located on Axel Heiberg Island in the Canadian H
 igh Arctic\, is the coldest and saltiest terrestrial spring discovered to 
 date. It is characterized by perennial discharges of subzero temperatures 
 (-5°C)\, hypersalinity (24% salinity)\, along with reducing (≈-165 mV)\, m
 icrooxic\, and oligotrophic conditions. It is rich in sulfates (10.0% w/w)
 \, dissolved H2S/sulfides (up to 25 ppm)\, ammonia (≈381 μM)\, and methane
  (11.1 g d-1). The LH spring system contains the outlet and the outflow ch
 annel. In the initial study of the LH channel sediment\, the results deter
 mined the microbial abundance by using fluorescent microscopy technique in
  the channel sediment\; also\, the study characterized the cultured repres
 entatives and confirmed that most of these isolates are halotolerant and p
 sychrotolerant microorganisms. The mineralization assays on the LH channel
  sediment revealed that the heterotrophic microorganisms remained active d
 own to -20°C. To determine the total microbial communities inhabiting at t
 he LH spring system\, the study demonstrated the microbial 16S rDNA and th
 e active 16S rDNA profiles for different sampling locations\, including th
 e outlet\, channel and the adjacent tundra. We identified that the Bacteri
 a from the five phyla (Bacteroidetes\, Proteobacteria\, Actinobacteria\, F
 irmicutes\, and Cyanobacteria) were the dominant bacterial groups at the L
 H spring system. In the archaeal communities\, microorganisms affiliated w
 ith three phyla (Euryarchaeota\, Crenarchaeota\, and Thaumarchaeota) were 
 identified. To determine its total functional and genetic potential\, we p
 erformed metagenomic analysis of the LH spring outlet microbial community.
  Reconstruction of the enzyme pathways responsible for bacterial nitrifica
 tion/denitrification/ammonification and sulfate reduction appeared nearly 
 complete in the metagenomic dataset. Stress-response genes for adapting to
  cold\, osmotic stress\, and oxidative stress were also abundant in the me
 tagenome. Comparing functional community composition of the LH spring to m
 etagenomes from other saline/subzero environments revealed a close associa
 tion between LH and another Canadian High Arctic permafrost environment\, 
 particularly in genes related to sulfur metabolism and dormancy. To identi
 fy the abundance and the presence of the featured genes (amoA and hcd) of 
 Thaumarchaea at the LH spring system\, we performed qPCR to assess their a
 bundance. A phylogenetic analysis was performed using the putative amino a
 cid sequences of these genes to identify their phylogenetic affiliation. T
 he copy numbers of thaumarchaeal amoA and hcd genes in LH channel sediment
  and the adjacent tundra were roughly 10 to a hundred-folds less than thos
 e reported in other environments. The phylogenetic tree of amoA showed sim
 ilar patterns of grouping as the analysis done by r16S rDNA. This thesis d
 emonstrates the microbial ecology\, diversity and activity at the LH sprin
 g system and provides knowledge for the microbiology studies on cryo- and 
 hypersaline environments.
DTSTART:20131021T141500Z
DTEND:20131021T141500Z
LOCATION:R3-037\, Raymond Building\, CA\, QC\, St Anne de Bellevue\, H9X 3V
 9\, 21111 Lakeshore Road
SUMMARY:Ph.D. Thesis Defense: Mr. Chih-Ying Lay: Microbial diversity\, acti
 vity\, and ecology of a hypersaline High Arctic spring system
URL:/nrs/channels/event/phd-thesis-defense-mr-chih-yin
 g-lay-microbial-diversity-activity-and-ecology-hypersal
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