Fig. 3

Growth characters and intramacrophage survival capabilities of S. agalactiae strains. A Genetic structure of the fruRKI operon in S. agalactiae. B Relative mRNA levels of the fruRKI genes. C Growth curves of the WT, ΔluxS, ΔfruRKI, and CΔfruRKI strains cultivated in THB. D Growth curves of the WT, ΔluxS, ΔfruRKI and CΔfruRKI strains cultivated in CDM supplemented 1% fructose. E Growth curves of the WT, ΔluxS, ΔfruRKI and CΔfruRKI strains cultivated in CDM supplemented 1% glucose. F Intracellular survival of the WT, ΔluxS, ΔfruRKI and CΔfruRKI strains in macrophages. G Intracellular survival of the WT, ΔluxS, ΔluxS:: fruI, ΔluxS:: fruK and ΔluxS:: fruR strains in macrophages. Data are presented as the mean ± SD of three independent experiments. *P < 0.05 or ***P < 0.001, indicates a significant difference between the indicated strain and the WT strain. ^# < 0.05, ^## < 0.01, or ^### < 0.001, indicates a significant difference between the indicated strain and the ΔluxS strain.