Publication Date:
2022-05-26
Description:
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole oceanographic Institution February 2010
Description:
Extensive genetic diversity has been discovered in the microbial world, yet mechanisms
that shape and maintain this diversity remain poorly understood. This thesis investigates
to what extent populations of the gamma-proteobacterial family, Vibrionaceae, are
ecologically specialized by investigating the distribution across a wide range of
environmental categories, such as marine invertebrates or particles in the water column.
Additionally, it seeks to determine whether in situ population distributions directly result
from a competitive advantage over other Vibrio populations. This was investigated by in
vitro competition assays on mixtures of native, sterilized particles. Generalist populations
were found to dominate the associations with marine invertebrates, consistent with a
model of high migration dominated population assembly. A majority of populations
occurred broadly within and among the different types of invertebrates sampled, with one
population being a near perfect generalist with regard to seasons, host taxa and body
regions. High variability across host individuals, consistent with a scenario of stochastic
clonal expansion, was especially pronounced in crab and zooplankton samples.
Specialization, demonstrated by specific and reproducible association with different
particle types in the water column, is more common than specialization within
invertebrate hosts. Co-existing Vibrio species show strong preferences for different types
of particulate matter in the water column suggesting that competition for limited
resources influences their evolution. While populations show different growth profiles on
particle derived substrates, relative growth advantages of specialist populations in
competition with other Vibrio populations on native particles may not be sufficient to
explain observed environmental distributions. Instead, populations may gain an
advantage on these particles by colonizing the living plant or zooplankton prior to death
and degradation into particulate matter. In summary, although vibrios are known
commensals of marine invertebrates, evidence suggests that population structure within
animals is fairly weak compared to suspended particles in the water column. This
highlights the importance of comparing multiple environmental categories and migration
among them to investigate population structure and adaptation.
Description:
I would like to thank the Linden Fellowship for their support during the Fall,
2003- Spring, 2004 and the Martin Family Society of Fellows for Sustainability for their
support during the Fall 2005. Work in this thesis was also made possible by support from
the following agencies: Woods Hole Center for Oceans and Human Health, which is funded jointly by the National Science Foundation (OCE-0430724) and the National
Institute for Environmental Health Sciences (P50 ES012742); DOE-Chicago (DE-FG02-
08ER64516); The Gordon and Betty Moore Foundation (Letter Agreement 1108).
Keywords:
Marine microbiology
;
Microbial diversity
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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