FIG 5.

Surface N-formyl-perosamine polysaccharides are responsible for Brucella camouflage. (A) Smooth B. abortus ΔwadC and rough Δper mutants were incubated with BALB/c bone marrow PMNs at the indicated MOIs in the presence of normal or inactivated mouse serum, and phagocytosis was recorded as described in the legend of Fig. 2. The inset corresponds to a PMN with internalized B. abortus Δper (MOI of 50); the infected cell was fixed and mounted with ProLong Gold Antifade reagent with DAPI and observed under the fluorescence microscope at a magnification of ×200. The image was cut from the microscope field, contrasted, and saturated using the hue tool to obtain suitable color separation. (B) Y. enterocolitica O:9 (MOI of 100) was incubated with BALB/c bone marrow PMNs in the presence of normal serum or serum with anti-Brucella antibody (2%), and the phagocytosis was recorded. (C) B. abortus 2308 and the ΔwadC mutant (10⁶ CFU) were incubated with normal or inactivated mouse serum or normal mouse serum containing antibodies against Brucella, and bacterial viability was recorded after 45 min of incubation. (D) B. abortus Δper was incubated in the presence of normal or inactivated mouse serum or with BALB/c bone marrow PMNs in normal serum, and the bacterial viability was estimated at the indicated times.