Exploring different methods of Exaiptasia pallida infection to follow Vibrio parahaemolyticus dissemination in the whole animal

Abstract

Abstract When studying host-pathogen interactions, the method of administration of the pathogen is a crucial parameter to control the injected dose of bacteria and the stress experienced by the animal during manipulation. Here we developed two models of infection (balneation or injection) of Exaiptasia pallida (E. pallida) by Vibrio parahaemolyticus expressing GFP (Vp-GFP). The injection, which provided better control of the bacteria quantity introduced inside the animal, induced a stress response with contraction and rejection of bacteria. We followed Vp-GFP dissemination by confocal microscopy over time at 6, 24 and 30 hours. During the early time of infection, bacteria adhering to the ectoderm were observed in both infection methods. At the latter time of infection Vp-GFP disappeared from ectoderm and appeared in the gastroderm. In case of injection, Vp-GFP were located in the gastroderm after 6 hours, whereas in the balneation case, bacteria reached the gastroderm until 24 hours. In both methods, bacteria disappeared from the ectoderm after 6 hours. In conclusion, by using Vp-GFP, we demonstrated for the first time that we can infect E. pallida and quantified the bacteria in whole animals. We also localized them in the different tissues, especially in mesenterial filaments, which are the main entry route of bacteria independently of the infection method.