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Department of Estuarine and Ocean Sciences MS Thesis Defense - by Ryan Nuttall

When: Monday, October 4, 2021
12:00 PM - 1:00 PM
Where: > See description for location
Description: The School for Marine Science and Technology
Department of Estuarine and Ocean Sciences
MS Thesis Defense

"Vibrio cyclitrophicus population - specific biofilm formation and association with marine copepods"

Ryan Nuttal

Dr. Pia Moisander (University of Massachusetts Dartmouth)

Dr. Erin Bromage (University of Massachusetts Dartmouth)
Dr. Mark Silby (University of Massachusetts Dartmouth)
Dr. Spencer Nyholm (University of Connecticut)

Monday, October 4, 2021
12:00 pm to 1:00 pm
UMass Dartmouth Campus, Room TEX-102
285 Old Westport Road, Dartmouth, MA
and via Zoom

Abstract: Vibrio spp. form a part of the microbiome of the highly abundant marine mesozooplankton termed copepods. The tendency of Vibrio to associate with copepods has been linked to transmission of cholera, and several Vibrio species cause disease through associations with marine macroinvertebrates and finfish which may use copepods as a food source. The biological mechanisms of the Vibrio-copepod association are largely unknown. The aims of this thesis were to: 1) compare biofilm formation of Vibrio isolated from copepods and closely related Vibrio originating from seawater, 2) visualize the attachment of Vibrio on live copepods and dead particles, and 3) investigate growth of Vibrio on live copepods. Two strain types of V. cyclitrophicus were studied that are separated by small genomic differences in biofilm formation loci. Two ‘L-strains’ were isolated from copepods and two ‘S-strains’ were included that originated from seawater.

It was expected that the L-strains would have a superior biofilm formation capacity, but in biofilm assays developed in this study, L- and S-strains formed similar biofilms in the presence of all sea salts, irrespective of carbon source, suggesting previously undescribed biofilm mechanisms are present in the S-strains. Calcium promoted biofilm formation and resulted in substantially denser biofilms in the L-strains, suggesting regulation of the pilus or polysaccharide pathways present in the L- but not in the S-strains. Calcium regulation may be important for colonization of shellfish by V. cyclitrophicus and other Vibrio spp. Colonization of Vibrio on Acartia tonsa copepods was observed by generating Green Fluorescent Protein -expressing strains and visualizing and quantifying attachment with fluorescence microscopy. Cells tended to localize on the antennae of live copepods, suggesting that vortices generated by animal movement and feeding promote bacterial attachment. L-strains attached to copepods at significantly higher numbers than the S-strains, suggesting that biofilms of L-strains are better at withstanding shear, or that these strains are more effective at evading the host’s immune responses. The data also demonstrate that V. cyclitrophicus cells grow epibiotically on live copepods after attachment, indicating that copepods can both selectively recruit and sustain Vibrio growth.

This study provides information about the complex biological mechanisms underlying the Vibrio association with marine zooplankton and particles and elucidates the V. cyclitrophicus metapopulation ecology. The V. cyclitrophicus – A. tonsa model used here could be useful in future studies on Vibrio-invertebrate associations.

Zoom Link:

Meeting ID: 925 4179 0588; Passcode: 201991

​For addtional information, please contact Sue Silva at
Contact: > See Description for contact information
Topical Areas: School for Marine Sciences and Technology, SMAST Seminar Series