Thrilled to see this story come to fruition!

Folks have known for years that adding magnesium to media rescues the lethality of deleting many 'essential' genes, but why? @eswaralab.bsky.social and @subtisilly.bsky.social say that free iron builds up in these mutants. Mg2+ mitigates this by redirecting metabolism towards limiting ROS production

Thank you! It’s been super fun to disentangle some of those complexities!

9/9 So proud of my mentee and co-author Pilar Horigian (@pilarhorigian.bsky.social) now a PhD student at UIC, and grateful to my Pl for his guidance throughout the development of this project. Excited for future work disentangling metal homeostasis and the cell envelope!

8/9 Together our results exposed, at least some aspects of, the magic behind the effects of magnesium and highlight the importance of cell envelope biogenesis on metal homeostasis. Our data also showed that antibiotic killing can be modulated through electron transport function and labile iron pools

7/9 Finally: does blocking cell wall synthesis with beta-lactams phenocopy our genetics? Yes!! Mg addition let otherwise WT cells grow in cefepime. Pushing cells toward fermentation, by limiting ETC function or promoting overflow metabolism, also protected them from cefepime killing.

6/9 We also observed that Mg (and glucose) reduces the strength of membrane potential, implying that cells may fine tune energy generation pathways differentially in the presence of magnesium.

5/9 Additionally, we demonstrated that promoting overflow metabolism by glucose addition OR restricting ETC function through the deletion of qoxABCD genes, allow cells to circumvent Fe/Mn intoxication (amplifies ROS production or impairs oxidative stress response).

4/9 Mg supplementation appears to activate ROS response systems and shrink the labile iron pool, which we think is what lets certain cell wall mutants grow. ROS from the electron transport chain, specifically the terminal quinol oxidase QoxABCD, is the main driver of Fe/Mn toxicity in Del-ezrA cells

3/9 Using genetics and biochemistry, we found the ezrA gpsB double mutant accumulates high levels of intracellular iron, fails to activate traditional ROS response systems, and produces elevated ROS. Similar but milder phenotypes appear in cells lacking EzrA alone or the class A PBP, PBP1.

2/9 The cell envelope is our forte in the Eswara lab (@eswaralab.bsky.social), so we tackled this 50-year-old mystery with our favorite proteins, EzrA and GpsB. Cells lacking both are synthetically sick and rescued by magnesium. We used that growth defect to better understand the Mg effect.

1/9 The enigmatic protective effects of magnesium have been known in the B. subtilis field for nearly 50 years. Adding large amounts of Mg to the growth medium allows the deletion of otherwise essential genes. Curiously, nearly all of these genes are involved in cell envelope biogenesis.