Lauren E. Bonefont

and 4 more

Mycobacterium abscessus (Mab) is highly drug resistant, and understanding regulation of antibiotic resistance is critical to future antibiotic development. Regulatory mechanisms controlling Mab’s β-lactamase (Bla Mab) that mediates β-lactam resistance remain unknown. S. aureus encodes a prototypical protease-mediated two-component system BlaRI regulating the β-lactamase BlaZ. BlaR binds extracellular β-lactams, activating an intracellular peptidase domain which cleaves BlaI to derepress blaZ. Mtb encodes homologs of BlaRI, that regulate the Mtb β-lactamase, blaC, but also additional genes related to respiration. We identified orthologs of blaRIMtb in Mab and hypothesized that they regulate blaMab. Surprisingly, neither deletion of blaRIMab nor overexpression of only blaIMab altered blaMab expression or β-lactam susceptibility. However, BlaI Mab did bind to conserved motifs upstream of several Mab genes involved in respiration, yielding a putative regulon that partially overlapped with BlaI Mtb. Prompted by evidence that respiration inhibitors including clofazimine (CFZ) induce the BlaI regulon in Mtb, we found that CFZ triggers induction of blaIRMab and its downstream regulon. Highlighting an important role for BlaRI Mab in adapting to disruptions in energy metabolism, constitutive repression of the BlaI Mab regulon rendered Mab highly susceptible to CFZ. In addition to our unexpected findings that BlaIR Mab does not regulate β-lactam resistance, this study highlights the novel role for mycobacterial BlaRI-type regulators in regulating electron transport and respiration.