Many animals depend on associations with bacterial symbionts for normal physiology. Though it is appreciated that many symbioses promote animal health, the contribution of strain diversity to symbioses remains poorly understood. The squid-vibrio model was utilized to investigate strain diversity. Co-isolated strains were recovered from a wild-caught squid and their phenotypic diversity was investigated with respect to motility, bioluminescence, competition, growth, and biofilm formation. The ability of the strains to colonize juvenile squid was measured.