Fig. 2

Growth of ‘Ca. B. cookevillensis’ in human macrophage-like cells. TEMs of ‘Ca. B. cookevillensis’ appearing to be within the nucleus (n) of human U937 macrophages at 24 h (a) and 48 h (b) following infection with an MOI of 10. At 24 h, bacteria are contained within the nucleoplasm surrounded by electron-translucent space within a vacuole (white triangle). The bilayer of the nuclear envelope is visible (white arrow). The nucleolus (nu) is also visible. By 48 h, larger numbers of bacteria are visible in the nuclear vacuoles and the vacuole fills the nucleus. A cytoplasmic vacuole with a single bacterium is also visible. c Confocal micrographs of FISH stains using probes specific for ‘Ca. B. cookevillensis’ in U937 cells (top) and an additional human macrophage cell line, THP-1 (bottom) at 48 h p.i. Nuclei and bacteria are also stained with DAPI. Inclusions filled with bacteria are visible for both cell lines. Bars, 10 μm