Meeting Abstract
28-2 Friday, Jan. 4 13:45 – 14:00 Noshing on Vibrio – How Grazing “Outside the Host” Determines “Fitness Inside the Host” CHEAM, D.*; HUEFFMEIER, B.W.; NISHIGUCHI, M.K.; New Mexico State University dcheam@nmsu.edu http://nishsymbiosislab.com
Vibrio fischeri can aggregate under stable conditions as a nonmobile community called a biofilm. Certain protozoans have a preference to feed on biofilms depending on the age and type of bacteria within the biofilm community. Protist grazing pressure can have multiple effects on bacterial biofilms including decreasing growth rates to triggering defense mechanisms that confer an increase in fitness. V. fischeri is a bacterial symbiont that resides in the light organs of sepiolid squids, forming a beneficial association by producing luminescence for a behavior termed counter-illumination. During the symbiosis, Vibrio bacteria produce biofilms within the squid light organ, allowing them to grow in high cell density, which regulates luminescence production. Given that Vibrio bacteria form biofilms both outside and inside the squid host, various factors may select for specific attributes for optimal biofilm production. Therefore, we examined whether biotic factors (e.g. grazing) outside the squid host were important for increasing biofilm production during symbiosis. We measured a total of nine different strains (free-living and symbiotic) of V. fischeri to determine whether free-living or symbiotic strains differed in their ability to form biofilm by experimentally evolving these strains for 500 generations under protozoan grazing pressure. Early (4 hour) or late (24 hour) biofilms at every 100 generations were subsequently examined for their ability to colonize juvenile squid hosts. V. fischeri are capable of evolving various defense mechanisms due to protist grazing pressure, which eventually effects the fitness during symbiosis with their squid hosts. Results of this study will provide a window to specific trade-offs that occur between abiotic and biotic pressures during environmentally transmitted beneficial associations.
