Metabolism‐lipid droplet‐nucleic acid crosstalk to regulate lipid storage and other cellular processes in oleaginous Rhodococcus bacteria

Abstract

Actinobacteria belonging to Mycobacterium and Rhodococcus genera are ableto synthesize and intracellularly accumulate variable amounts of triacylglycerols(TAG) in the form of lipid droplets (LDs). The lipid storage capacity ofLDs in cells is controlled by the balance between lipogenesis and lipolysis. Thegrowth of LDs in bacterial cells may be directly promoted by TAG biosynthesis,whereas TAG degradation might result in the reduction of LD sizes and lipidstorage capacity. Therefore, LD formation and turnover have to be precisely regulatedto maintain a balanced lipid distribution, coupling gene regulation withthe metabolic state of the cell. In eukaryotic cells, LDs have emerged as criticalmediators of diverse cellular responses, including fatty acid trafficking andmodulation of transcriptional programs. Recent studies performed in mycobacteriaand rhodococci suggested the existence of similar crosstalk mechanismsbetween lipid metabolism, LDs, and gene expression regulation in cells. Thisreview connects and organizes results of different studies in a comprehensiveframework for providing evidence of “lipid metabolism-LDs-genomic DNA”crosstalk occurring in TAG-accumulating actinobacteria. We provide examplesindicating that bacterial cells evolved sensing mechanisms that detect lipidmetabolites changes as indicators of metabolic states, and adapt their transcriptionalprofiles through epigenetic-like mechanisms mediated by LD-associatedproteins. Here, we describe the molecular interconnections of this coupling systemand the main role of each component that integrates the information aboutthe cellular metabolic state into the regulation of lipogenesis, LD formation andtranscription in oleaginous bacteria.