Print Friendly printer friendly
 Events
Tue 6 Sep 2016, 9:00am SPECIAL
MATX 1102
Qualifying Exams - Analysis
MATX 1102
Tue 6 Sep 2016, 9:00am-12:00pm

Details

For more information on Qualifying Exams, please visit http://www.math.ubc.ca/Grad/QualifyingExams/index.shtml
Lunch will be provided in  MATX 1101 for students writing the Analysis exam.
hide
Tue 6 Sep 2016, 1:00pm SPECIAL
MATX 1102
Qualifying Exams - Algebra
MATX 1102
Tue 6 Sep 2016, 1:00pm-4:00pm

Details

For more info, please visit http://www.math.ubc.ca/Grad/QualifyingExams/index.shtml
hide
Tue 6 Sep 2016, 1:00pm SPECIAL
MATX 1102
Qualifying Exams - Differential Equations
MATX 1102
Tue 6 Sep 2016, 1:00pm-4:00pm

Details

For more info, please visit http://www.math.ubc.ca/Grad/QualifyingExams/index.shtml
hide
Tue 6 Sep 2016, 4:30pm SPECIAL
Math 125
Department Graduate Orientation
Math 125
Tue 6 Sep 2016, 4:30pm-6:00pm

Details


hide
Stilianos Louca
Mathematics, UBC
Tue 20 Sep 2016, 12:30pm SPECIAL
Room 200, Graduate Student Centre, 6371 Crescent Road, UBC
Doctoral Exam: The ecology of microbial metabolic pathways
Room 200, Graduate Student Centre, 6371 Crescent Road, UBC
Tue 20 Sep 2016, 12:30pm-2:30pm

Details

Abstract:
Microbial metabolic activity drives biogeochemical cycling in virtually every ecosystem. Yet, microbial ecology and its role in ecosystem biochemistry remain poorly understood, partly because the enormous diversity found in microbial communities hinders their modeling. Despite this diversity, the bulk of global biogeochemical fluxes is driven by a few metabolic pathways encoded by a small set of genes, which through time have spread across microbial clades that can replace each other within metabolic niches. Hence, the question arises whether the dynamics of these pathways can be modeled regardless of the hosting organisms, for example based on environmental conditions. Such a pathway-centric paradigm would greatly simplify the modeling of microbial processes at ecosystem scales.
Here I investigate the applicability of a pathway-centric paradigm for microbial ecology. By examining microbial communities in replicate "miniature" aquatic environments, I show that similar ecosystems can exhibit similar metabolic functional community structure, despite highly variable taxonomic composition within individual functional groups. Further, using data from a recent ocean survey I show that environmental conditions strongly explain the distribution of microbial metabolic functional groups across the world's oceans, but only poorly explain the taxonomic composition within individual functional groups. Using statistical tools and mathematical models I conclude that biotic interactions, such as competition and predation, likely underlie much of the taxonomic variation within functional groups observed in the aforementioned studies. The above findings strongly support a pathway-centric paradigm, in which the distribution and activity of microbial metabolic pathways is strongly determined by energetic and stoichiometric constraints, whereas additional mechanisms shape the taxonomic composition within metabolic guilds.

These findings motivated me to explore concrete pathway-centric mathematical models for specific ecosystems. Notably, I constructed a biogeochemical model for Saanich Inlet, a seasonally anoxic fjord with biogeochemistry analogous to oxygen minimum zones. The model describes the dynamics of individual microbial metabolic pathways involved in carbon, nitrogen and sulfur cycling, and largely explains geochemical depth profiles as well as DNA, mRNA and protein sequence data. This work yields insight into ocean biogeochemistry and demonstrates the potential of pathway-centric models for microbial ecology.

Note for Attendees

Latecomers will not be admitted.
hide
 
Top