Ancient bacteria-amoeba relationships and pathogenic animal bacteria

Abstract

Long before bacteria infected humans, they infected amoebas, which remain a potentially important reservoir for human disease. Diverse soil amoebas including Dictyostelium and Acanthamoeba can host intracellular bacteria. Though the internal environment of free-living amoebas is similar in many ways to that of mammalian macrophages, they differ in a number of important ways, including temperature. A new study in PLOS Biology by Taylor-Mulneix et al. demonstrates that Bordetella bronchiseptica has two different gene suites that are activated depending on whether the bacterium finds itself in a hot mammalian or cool amoeba host environment. This study specifically shows that B. bronchiseptica not only inhabits amoebas but can persist and multiply through the social stage of an amoeba host, Dictyostelium discoideum.

Fig 1. Diagram of survival strategies of intracellular bacteria within amoebas.

The figure represents two general strategies that intracellular bacteria deploy to survive within amoebas. They can escape from the phagosome (Fig 1A) or stay within the phagosomal vacuole but modify it (Fig 1B). Green, intranuclear bacteria; yellow, bacteria that escape into the cytosol; blue, carried Burkholderia; purple, B. bronchiseptica; red, L. pneumophila.