Figure 5: Analyzing cell morphology by transmission electron microscopy and bacterial surface structures by SDS-PAGE.

(a,b) Transmission electron micrographs of S. suis strains. Bars in upper (magnification is 25000) and lower panels (magnification is 5000) were200 and 1000 nm respectively. Bacteria were cultured in TSB containing 10% fetal bovine serum (a). Measurement of capsule thickness as described in ‘Method’ during exponential phase (O.D₆₀₀ = 0.7 ~ 1.0) revealed that the thickness of capsules for wild type (WT) and codY mutated (ΔcodY) strains were 81.23 ± 2.91 nm and 41.27 ± 3.41 nm respectively. The capsule thickness during stationary phase (O.D₆₀₀ ≥ 1.2) showed that the thickness of capsules for wild type (WT) and codY mutated (ΔcodY) strains were 81.16 ± 2.22 nm and 52.28 ± 4.06 nm respectively. (b). The data are expressed as means ± S.D. The means of two groups were compared using Student’s t test (unpaired, 2-tailed). ***P < 0.001; *P < 0.05 (c) SDS-PAGE analysis of the bacterial surface-associated proteins. The bacteria grown were re-suspended in 1 ml of 10 mM sodium phosphate (pH 5.5), pelleted by centrifugation at 13,000 × g for partially remove proteins not associated with cell surface structures, and then resuspended in 0.2 ml of 10 mM sodium phosphate (pH 5.5). The bacterial suspension was pushed through a 25 G needle four to five times to shear the surface structures and proteins from the bacteria, and then centrifuged at 13,000 × g. 20 μl of the supernatant was used for SDS-PAGE analysis.