PIKFYVE and infection: Infection of Raw264.7 macrophage–like cells with L. pneumophila Paris WT expressing TEM1–LtpM or -LtpD, but not the corresponding T4SS-deficient ΔdotA strains or WT bacteria expressing a TEM1 fusion to the housekeeping protein Fab1, resulted in a sharp increase of the ratio of the fluorescence signals of the cleaved β-lactam product over the substrate (Fig. 1A), showing that LtpM is translocated into host cells by the Dot/Icm T4SS.