Symbiotic Amoeba Host-Microbe Interactions

We used three native host strains of D. discoideum (QS395, QS433, QS859), three nonnative D. discoideum strains (QS4, QS17, QS18), and three P. bonniea symbiont strains (bb395, bb433, bb859). All D. discoideum strains were previously isolated from Mountain Lake Biological Station in Virginia, USA. The native host strains had been cured of their symbionts using tetracycline and verified as symbiont-free using PCR. For each replicate, host (with food bacteria Klebsiella pneumoniae) and symbiont strains were grown from freezer stock on SM/5 plates (2 g glucose, 2 g BactoPeptone (Oxoid), 2 g yeast extract (Oxoid), 0.2 g MgCl₂, 1.9 g KH₂PO₄, 1 g K₂HPO₄ and 15 g agar per liter). KK2 buffer (2.2 g KH2PO4 monobasic and 0.7 g K2HPO4 dibasic per liter) was used throughout for handling bacteria, D. discoideum spores and amoebas.