Previously uncharacterized Micrococcus luteus membrane protein regulates hypoxic stress response by promoting normal oxygen metabolism

Previous studies in our laboratory have identified several proteins that are overexpressed in dormant state, thus likely involved in dormancy regulation in Micrococcus luteus. In my study, we focus on one of these proteins, a previously uncharacterized hypothetical protein (Hyp730). Specifically, we endeavored to identify the function of this protein by genomic deletion of hyp730 and growing the resulting knockout strain under hypoxic and nutrient deprivation stress. We also used enzymatic, spectroscopic, and transcriptomic assays to predict Hyp730’s mechanism of action. We also purified the protein and used computational models to evaluate its structure. The Δhyp730 knockout strain exhibited increased viability and culturability under hypoxic conditions. The O2 consumption assays showed that cytochrome bo activity was functionally eliminated in the Δhyp730 knockout strain, forcing cells to use the cytochrome bd complex. At which point, as a terminal oxidase, the oxygen scavenging functionality of cytochrome bd may help to explain the increased ability to survive in hypoxic conditions. Spectroscopic analysis showed a decrease in the relative abundance of cytochrome bo compared to cytochrome bd. While the transcriptomics data showed no significant change in either complex but did show an upregulation of genes related to the glyoxylate shunt. Hyp730 phenotype arose directly from the activity of the cytochrome bo complex, with the changes in expression compensating for the loss of this activity. However, more studies are needed to confirm this association.