Quorum sensing describes the bacterial signaling process involving the synthesis and detection of small molecules called autoinducers. How quorum sensing occurs within bacterial populations within a host remains poorly characterized, in part because of the natural variation in size and biogeography of the cellular aggregates that form along host tissues. We utilize the symbiosis between the squid Euprymna scolopes and the bacterium Vibrio fischeri to evaluate quorum sensing across spatially segregated symbionts within the animal.