[ODP-139] Bordetella bronchiseptica utilizes Acanthamoeba castellanii as a temporal niche
Apart from its ability to infect animals, Bordetella bronchiseptica (Bb) is considered to persistently survive in the environment; however, its environmental lifestyle is poorly understood. In this study, we explored the possible interaction between Bb and Acanthamoeba castellanii (Ac) as a representative of environmental protozoa. Unlike bacteria that serve as amoeba food sources, phagocytosed Bb resisted amoeba digestion and escaped to extracellular milieu through contractile vacuoles (CVs), intracellular compartments involved in osmoregulation. Furthermore, Bb survived and proliferated for at least 28 days of co-culture with the amoeba. Bordetellae harbor the two-component system called BvgAS that controls the reversible phenotypic conversions between an avirulent (Bvg- phase) and a virulent (Bvg+ phase) phenotype. Bb mutant locked in the Bvg- phase but not in the Bvg+ phase survived and proliferated in the co-culture with the amoeba. Microscopic analyses revealed that the Bvg+-phase locked mutant was more efficiently internalized and targeted by the amoeba digestion pathway than the Bvg--phase locked mutant. After 7 days of co-culture, the dead cells of the Bvg+-phase locked mutant were accumulated in giant food vacuoles (GFVs). These data suggest that Bb resists predation by Ac in a Bvg phase-dependent manner and that Ac is a potential transient environmental host for Bb.