Participant Support Costs

  • Mandel, Mark (Subproject PI)

Project: Research project

Project Details


Page A
Microbial symbioses are prevalent in animals and are crucial to the health and development
of both partners. These relationships have evolved robust mechanisms to ensure the faithful
transmission of symbionts during each new host generation. This proposal applies modern genomic
and genetic methods to examine how host specificity develops in a horizontally transmitted
animal-microbe symbiosis. The question of colonization fidelity is fundamental to understanding
microbial transmission in beneficial and pathogenic colonization, the animal host range of
symbiotic bacteria, the maintenance of microbial diversity, and the influence of environmental
factors (e.g., climate change) on host-symbiont coevolution. By taking an integrative approach
that encompasses natural populations, genomes, pathways, and genes, this proposal seeks to
understand the molecular mechanisms that maintain symbiont-host fidelity and facilitate co-evolutionary
dynamics in horizontally-transmitted bacterial symbionts.
Intellectual Merit :
The proposal focuses on the binary association between Vibrio fischeri bacteria and the bobtail
squid hosts. Preliminary data have revealed the importance of biofilm formation (bacterial
aggregation) during host colonization, both in V. fischeri colonization of squid and in many
bacterial colonization systems. In the canonical squid symbiont ES114, the RscS sensor kinase
activates biofilm genes that are necessary for normal host colonization. We have identified
two classes of symbionts that are closely related to ES114 but that use distinct mechanisms.
The first uses a completely novel system for colonization, whereas the second uses the same
biofilm target genes without the known regulator. To study how evolutionary changes in bacterial
signal transduction influence the robustness of partner stability as a mutualism evolves,
we will use the two comparative systems and evaluate the hypotheses that (i) small genetic
changes fundamentally alter the manner by which microbes interact with animals, and (ii) changes
in bacterial aggregation form the basis for multiple evolutionary transitions in host partner
choice. To test these hypotheses we will determine the genetic factors that regulate biofilm
formation and host colonization in each strain and we will evaluate the manner by which each
genetic lesion influences biofilm signal transduction across V. fischeri strains. Completion
of these objectives will advance our understanding of how biofilm formation, an important
bacterial behavior, influences the development and evolution of partner choice during symbiotic
Broader Impacts :
This work examines closely-related bacterial symbionts to identify how partnerships with animals
evolve. The ability to study bacterial genetic networks at high resolution will be applicable
to understanding how signaling pathways in bacteria respond to other shifts, such as those
introduced by climate change or other ecological processes. This will be accomplished with
unique training opportunities that involve undergraduate and doctoral students in high-throughput
modern methods such as bacterial genome sequencing, genome assembly, and the associated computational
skills. A pilot workshop is proposed that integrates with the research aims and trains undergraduate
and graduate students in modern bioinformatics techniques. A plan is presented to disseminate
results locally, regionally, and nationally; at the regional level a new beneficial microbes
symposium is proposed to enhance research
Effective start/end date8/1/157/31/18


  • National Science Foundation (IOS-1456963)


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