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dc.contributor.authorAxelrod, Kevin Connoren_US
dc.date.accessioned2017-07-25T14:42:05Z
dc.date.created2016-05en_US
dc.date.issued2016-05-04en_US
dc.date.submitted2016en_US
dc.identifier.citationAxelrod, Kevin Connor. 2016. Bistable dynamics in microbial ecology and systems biology. Doctoral dissertation, Harvard University, Graduate School of Arts & Sciences.en_US
dc.identifier.urihttp://nrs.harvard.edu/urn-3:HUL.InstRepos:33493470
dc.description.abstractBistability, in which a system has two stable states, is a common property of many dynamic systems. This thesis explores the properties of such systems across a range of length scales, from gene circuits to ecosystems. Cells often store memories of environmental stimuli using bistable gene circuits. High fidelity memory storage requires that a state has a long lifetime. However, an underappreciated aspect of stable memory is that the distance from a bifurcation could determine how sensitive a state is to perturbations in the extracellular environment. We predict that cell memory should become increasingly sensitive to perturbations near a bifurcation and test this idea in three different gene circuits: a toggle switch, the yeast galactose utilization network, and the E. coli lactose utilization network. In a second study, we explore how the environmental context in which two species interact can influence their mode of interaction. Two species in nature often form reciprocally beneficial partnerships termed mutualisms, but in certain environmental regimes the species might shift to competing with one another for resources. This mutualism-competition transition has been understudied in experimental ecosystems. Using a synthetic yeast cross-feeding mutualism, we modulate the degree to which two partners rely on each other by supplementing the cells with variable amounts of nutrients. Surprisingly, we find that as the amount of supplemented nutrients is increased, the system passes through eight qualitatively distinct dynamic regimes: extinction, obligatory mutualism, obligatory/facultative mutualism, facultative mutualism, parasitism, amensalism, competition, and competitive exclusion. In a third study, we probe how population growth dynamics can influence the probability of evolutionary rescue. Natural populations frequently face harsh environments in which their death rate exceeds their birth rate and population size tends toward zero. In such scenarios, populations can either go extinct, migrate to a better habitat, or adapt to the harsh environment. Natural populations often exhibit an “Allee effect,” in which populations grow slowly at low density due to struggles with such behaviors as finding a mate or collective hunting. We hypothesize that the presence of an Allee effect could impede evolutionary rescue and confirm this hypothesis in a model laboratory yeast ecosystem.en_US
dc.description.sponsorshipBiophysicsen_US
dc.format.mimetypeapplication/pdfen_US
dc.language.isoenen_US
dash.licenseLAAen_US
dc.subjectBiophysics, Generalen_US
dc.titleBistable dynamics in microbial ecology and systems biologyen_US
dc.typeThesis or Dissertationen_US
dash.depositing.authorAxelrod, Kevin Connoren_US
dc.date.available2017-07-25T14:42:05Z
thesis.degree.date2016en_US
thesis.degree.grantorGraduate School of Arts & Sciencesen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
dc.contributor.committeeMemberCohen, Adam E.en_US
dc.contributor.committeeMemberKlein, Allon M.en_US
dc.contributor.committeeMemberSpringer, Michaelen_US
dc.contributor.committeeMemberHogle, James M.en_US
dc.type.materialtexten_US
thesis.degree.departmentBiophysicsen_US
dash.identifier.vireohttp://etds.lib.harvard.edu/gsas/admin/view/853en_US
dc.description.keywordsBistability; ecologyen_US
dash.author.emailkevin.c.axelrod@gmail.comen_US
dash.contributor.affiliatedAxelrod, Kevin


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