Figure 2.

Nitrogen/carbon ratio governs TAG accumulation as ILI in Mycobacterium abscessus. (A) M. abscessus cells were grown in minimal salt medium containing either 1 g/L or 0.05 g/L NH₄Cl and 1% Gly as sole carbon source. Cultures were collected after an 8 h, 24 h or 48 h incubation period, lyophilized and equal amounts of dry cells used for apolar lipid extraction. TAG levels from each culture were analysed by TLC with triolein as standard. The TLC plate (left panel) is representative of two independent experiments. Right panel corresponds to TLC densitometric analysis of relative TAG levels in each sample, with cultures in exponential phase in classic 7H9TG^OADC used as reference. Results are expressed as mean values ± SD of two individual experiments. TAG band intensities were compared using a one-way ANOVA test where * corresponds to a p-value < 0.05. (B) Thin section of an in vitro culture of M. abscessus in classical 7H9^OADC medium. The scale bar represents 1 µm. (C) Thin section of an in vitro culture of M. abscessus in MSM NL Gly 1% medium. Right panel is a zoomed-in picture providing a better view and resolution of ILI. Scale bars represent 1 µm. (D) TAG levels from M. abscessus grown in MSM NL Gly. Cultures were collected after a 24 h or 48 h incubation period, lyophilized and equal weights of dry cells used for apolar lipid extraction. TAG levels from WT, Δtgs1, Δtgs2 and their respective complemented strains were analysed by TLC with triolein as standard. TLC densitometric analysis of relative TAG levels in each genetic background, with cultures from WT M. abscessus used as a reference. Results are expressed as mean values ± SD of two independent experiments. TAG band intensities of WT and Δtgs1 were compared using a one-way ANOVA test where * corresponds to a p-value < 0.05.