Vibrio cholerae-Acanthamoeba castellanii interaction showing endosymbiont-host relation

The causative agents of cholera Vibrio cholerae 01 and 0139 species are extracellular and waterborne bacteria, which lose to predators in aquatic environment. Recently, it was shown that V. cholerae survived intracellularly during interaction with the free-living amoeba Acanthamoeba castellanii. The aim of this study is to examine symbiosis between these microorganisms. The interaction between V. cholerae 01 classical, V. cholerae 01 El Tor, and V. cholerae 0139 and A. castellanii, respectively, was studied by viable counts of singly and co-cultivated microorganisms using gentamicin assay, microscopy and statistical analysis. Symbiosis between A. castellanii and V. cholerae was studied by recultivation of A. castellanii hosting intracellular V. cholerae as endosymbionts. The results showed an enhanced growth and survival of co-cultivated V. cholerae species in comparison to singly cultivated bacteria. V. cholerae grew in the cytoplasm of A. castellanii trophozoites and bacteria were also found in cysts. Intracellular growth and survival of the bacteria did not inhibit growth of A. castellanii. Growth and survival of both amoebae and bacteria in recultivation of A. castellanii harbouring intracellular V. cholerae indicate endosymbionts-host relation between these microorganisms.