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. Mycobacterium tuberculosis (Mtb) encodes homologs of BlaRI (which we will denote as BlaIR to reflect the inverted gene order in mycobacteria) that regulate not only the Mtb β-lactamase, blaC, but also additional genes related to respiration. We identified orthologs of blaIR_Mtb in Mab and hypothesized that they regulate bla_Mab. Surprisingly, neither deletion of blaIR_Mab nor overexpression of only blaI_Mab altered bla_Mab 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 induce the BlaI regulon in Mtb, we found that clofazimine triggers induction of blaIR_Mab and its downstream regulon. Highlighting an important role for BlaIR_Mab in adapting to disruptions in energy metabolism, constitutive repression of the BlaI_Mab regulon rendered Mab highly susceptible to clofazimine. In addition to our unexpected findings that BlaIR_Mab does not regulate β−lactam resistance, this study highlights the novel role of mycobacterial BlaRI-type regulators in regulating electron transport and respiration.

中文翻译：

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非典型脓肿分枝杆菌 BlaRI 直系同源物介导能量代谢的调节，但不介导 β-内酰胺耐药性


脓肿分枝杆菌 （Mab） 具有高度耐药性，了解抗生素耐药性的调节对于未来的抗生素开发至关重要。控制介导 β-内酰胺耐药的 Mab β-内酰胺酶 （Bla_Mab） 的调节机制仍然未知。金黄色葡萄球菌编码一种原型蛋白酶介导的双组分系统 BlaRI，可调节 β-内酰胺酶 BlaZ。BlaR 结合细胞外 β-内酰胺，激活细胞内肽酶结构域，该结构域裂解 BlaI 以去抑制 blaZ。结核分枝杆菌 （Mtb） 编码 BlaRI 的同源物（我们将其表示为 BlaIR 以反映分枝杆菌中的倒置基因顺序），该同源物不仅调节 Mtb β-内酰胺酶 blaC，还调节与呼吸相关的其他基因。我们在 Mab 中鉴定了 blaIR_Mtb 的直系同源物，并假设它们调节 bla_Mab。令人惊讶的是，blaIR_Mab 的缺失和仅 blaI_Mab 的过表达均未改变 bla_Mab 表达或 β-内酰胺敏感性。然而，BlaI_Mab 确实与几个参与呼吸作用的 Mab 基因上游的保守基序结合，产生与 BlaI_Mtb 部分重叠的推定调节子。有证据表明，包括氯法齐明在内的呼吸抑制剂在 Mtb 中诱导 BlaI 调节子，我们发现氯法齐明触发 blaIR_Mab 及其下游调节子的诱导。 BlaIR Mab 调节子的组成型抑制使 Mab 对氯法齐明高度敏感，这凸显了 BlaIR_{Mab 在}适应能量代谢中断方面的重要作用。除了我们出乎意料地发现 BlaIR_Mab 不调节 β−内酰胺耐药性外，本研究还强调了分枝杆菌 BlaRI 型调节因子在调节电子传递和呼吸方面的新作用。