Francisella tularensis subspecies holarctica´s adaptation to protozoan and mammal hosts

• The long co-existence of bacteria and protozoa in natural ecosystems has led to the evolution of different bacterial predation-resistance mechanisms1, which in turn may have triggered development of mammal pathogens2, such as the tularemia bacterium Francisella tularensis3. We studied links between environmental persistence and pathogenicity of Francisella tularensis subsp. holarctica (F. t. holarctica), by comparing its growth in association with an aquatic amoeba and a murine macrophage. A virulent wild-type strain and four isogenic mutations with different functional protein deletions were compared; DsbA4, 5 a membrane lipoprotein with disulfide oxidoreductase activity important for proper folding in Francisella tularensis; Hfq6 a pleiotropic regulatory RNA binding protein; PilA7, 8 a type IV pilus subunit and PglA9 a protein involved in O-linked protein glycosylation. DsbA was found to be essential for bacterial growth in association with both amoeba and macrophage, while PglA did not affect bacterial persistence in any of the hosts. Absence of PilA and Hfq had marked negative effect on the bacterial cell counts in amoeba, while growth was only slightly impaired in the macrophage. Functional similarities for bacterial persistence in both hosts highlight eco-evolutionary links between persistence of intracellular pathogenic bacteria in aquatic systems and mammal hosts.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

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