Figure 3. Host ACSLs activate bacterial branched-chain fatty acids (FA) iso-C15:0 and anteiso-C15:0 that are of C. trachomatis (Ct) origin.

An FA competition assay was performed with uninfected and infected cells (see Methods). HeLa cells were infected (or left uninfected) with Ct L₂. After 24 hpi, cells were harvested and lysed. The lysates were incubated with radiolabeled palmitic (C16:0) (A) or radiolabeled oleic acid (C18:1) (B), and an excess of the indicated competitor branched-chain FA, iso-C15:0 or anteiso-C15:0. No competitor was added to the control samples. The data were normalized to the signal of the mock or mock-infected control samples. Values (mean ± standard error for three independent experiments) are shown. The asterisks indicate statistically significant differences between each condition compared to the control by the two-tailed t- test; (ns: not significant, ^∗p < 0.05, ^∗∗p < 0.01, ^∗∗∗p < 0.001).