MmbR, a master transcription regulator that controls fatty acid β‐oxidation genes in Mycolicibacterium smegmatis

Abstract

Summary An unusually high lipid content and a complex lipid profile are the most distinctive features of the mycobacterial cell envelope. However, our understanding of the regulatory mechanism underlying mycobacterial lipid metabolism is limited, and the major regulators responsible for lipid homeostasis remain to be characterized. Here, we identified MmbR as a novel master regulator that is essential for maintaining lipid homeostasis in Mycolicibacterium smegmatis. We found that MmbR controls fatty acid β‐oxidation and modulates biofilm formation in Mycolicibacterium smegmatis. Although MmbR possesses the properties of nucleoid‐associated proteins, it acts as a TetR‐like transcription factor, directly regulating and intensively repressing the expression of a group of core genes involved in fatty acid β‐oxidation. Furthermore, both long‐chain acyl‐Coenzyme A and fatty acids appear to regulate the signal molecules modulated by MmbR. The deletion of mmbR led to a significant reduction in intracellular fatty acid content and a decrease in the relative lipid composition of the biofilm. The lack of mmbR led to morphological changes in the mycobacterial colony, defects in biofilm formation and enhanced sensitivity to anti‐tuberculosis drugs. Our study is the first to establish a link between the transcriptional regulation of fatty acid β‐oxidation genes and lipid homeostasis in mycobacteria.

PatA Regulates Isoniazid Resistance by Mediating Mycolic Acid Synthesis and Controls Biofilm Formation by Affecting Lipid Synthesis in Mycobacteria

“…The synthesis of lipids can affect the mycobacterial biofilm formation ( 23 – 25 ). Considering the effects of PatA on mycobacterial biofilm formation, we hypothesized that PatA might regulate the synthesis of lipids in mycobacteria.…”

Lsr2 acts as a cyclic di-GMP receptor that promotes keto-mycolic acid synthesis and biofilm formation in mycobacteria

“…The cells were collected, and genomic DNA was extracted with a bacterial genome extraction kit (#DN1101, Aidlab). Furthermore, the sequences near the insertion site of the transposon were amplified by thermal asymmetric PCR and sequenced to analyze the location of the transposon 19 , 48 . The primers for ydeH overexpression and transposon insertion mutant sequence analysis are shown in the Source data file (Primer list).…”

“…5 mL of mycobacterial suspension with an OD 600 of 0.3 was inoculated into a 12-well PVC microtiter dishes and was incubated at 30 °C without shaking for 5 days to observe biofilms formation at gas–liquid surface. 100 μL mycobacterial suspension with an OD 600 of 0.1 was used to quantify the biofilm formation by crystal violet staining assay 10 , 48 . Mycobacterial suspension was incubated for 48 h at 37 °C with shaking at 80 rpm in 96-well PVC microtiter dishes.…”

“…M. smegmatis strains were grown to OD 600 1.2 in 7H9 medium and harvested for bacterial lipidomic analysis. Lipid extraction, ultra-performance liquid chromatography, mass spectrometry, and lipid structural analyses were performed at Novo gene (Beijing, China) 48 . Bacterial cells (100 mg) were mixed with 0.75 mL methanol (#R40121, Thermo Fisher), which were vortexed in a glass tube with a Teflon lined cap.…”

Engineering biofilm matrix for efficient biofilm-mediated contaminant removal

“…Listeria monocytogenes [138]. Deletion of a gene encoding a TetR-like transcriptional regulator, MmbR, for fatty acid beta-oxidation and biofilm formation in Mycolicibacterium smegmatis significantly decreased the intracellular fatty acids and the total lipid content in the biofilm [139].…”