Vibrio fischeriexhibit the growth advantage in stationary-phase phenotype

Abstract

Vibrio fischeri are bioluminescent marine bacteria that can be isolated from their symbiotic animal partners or from ocean water. A V. fischeri population increases exponentially inside the light organ of the Hawaiian bobtail squid (Euprymna scolopes) while the host is quiescent during the day. This bacterial light organ population reaches stationary phase and then remains high during the night, when the squid use bacterial bioluminescence as a counter-predation strategy. At dawn, host squid release 90%-95% of the light organ contents into the ocean water prior to burying in the sand for the day. As the squid sleeps, the cycle of bacterial population growth in the light organ begins again. These V. fischeri cells that are vented into the ocean must persist under typical marine low nutrient conditions until they encounter another opportunity to colonize a host. We hypothesized that because V. fischeri regularly encounter cycles of feast and famine in nature, they would exhibit the growth advantage in stationary phase (GASP) phenotype. We found that older V. fischeri cells exhibit a Class 2 GASP response in which old cells increase dramatically in frequency while the population of young V. fischeri cells remains almost constant during co-incubation.