Figure 5.

Loss of TDO-mediated antibacterial functions in HeLa-hTDO cells under low oxygen conditions. Infection experiments: HeLa-hTDO cells were incubated under different oxygen conditions (1–20% O₂) for 72 h with or without tetracycline (160 ng/mL) and afterwards infected with Enterococcus faecalis in the presence or absence of additional tryptophan. (a) After 24 h the bacterial growth was determined by measurement of OD_620 nm, in 3 independent experiments with three replicates each. (b) Determination of colony forming units by serial dilution and summary of 7 independent experiments. Significant alterations of microbial growth as compared to the normoxia control are marked with asterisks (^∗ p ≤ 0.05; ^∗∗ p ≤ 0.01; ^∗∗∗ p ≤ 0.001; ^∗∗∗∗ p ≤ 0.0001) and were calculated by a two-tailed, unpaired t-test. The bars indicate the mean value ± SEM (a) or SD (b).