Cholesterol metabolism and intrabacterial potassium homeostasis are intrinsically related in <i>Mycobacterium tuberculosis</i>

SUMMARY Potassium (K + ) is the most abundant intracellular cation, but much remains unknown regarding how K + homeostasis is integrated with other key bacterial biology aspects. Here, we show that K + homeostasis disruption (CeoBC K + uptake system deletion) impedes Mycobacterium tuberculosis (Mtb) response to, and growth in, cholesterol, a critical carbon source during infection, with K + augmenting activity of the Mtb ATPase MceG that is vital for bacterial cholesterol import. Reciprocally, cholesterol directly binds to CeoB, modulating its function, with a residue critical for this interaction identified. Finally, cholesterol binding-deficient CeoB mutant Mtb are attenuated for growth in lipid-rich foamy macrophages and in vivo colonization. Our findings raise the concept of a role for cholesterol as a key co-factor, beyond its role as a carbon source, and illuminate how changes in bacterial intrabacterial K + levels can act as part of the metabolic adaptation critical for bacterial survival and growth in the host.