The outer layer of the gram-negative bacterial cellular envelope contains an outer membrane (OM), which surrounds the bacteria and protects it from the environment. The OM is largely impermeable to both large and hydrophobic molecules, leading to the intrinsic resistance of gram-negative bacteria to many antibiotics. In fact, this makes gram-negative bacteria inherently orders of magnitude more resistant to many antibiotics than gram-positive bacteria. Due to this permeability barrier, the last new class of antibiotics treating gram-negative infections was developed in the 1960’s.

Given the importance of the OM for antibiotic resistance, it is imperative to clarify the mechanisms of OM maintenance and adaptation during stress. The overarching goal of my lab is to understand the mechanisms that strengthen the outer membrane (OM) permeability barrier of gram-negative bacteria during stress. The lab’s general approach is to use genetics and biochemistry to interrogate (i) changes to the barrier during stress, (ii) the mechanisms that strengthen the barrier, and (iii) the role of these changes in antibiotic resistance and pathogenesis.

Please visit the Mitchell Lab website for more information about the lab and our current projects.

1. Rai, AK, Sawasato, K, Bennett, HC, Kozlova, A, Sparagna, GC, Bogdanov, M et al.. Genetic evidence for functional diversification of gram-negative intermembrane phospholipid transporters. PLoS Genet. 2024;20 (6):e1011335. doi: 10.1371/journal.pgen.1011335. PubMed PMID:38913742 PubMed Central PMC11226057.
2. Saenkham-Huntsinger, P, Ritter, M, Donati, GL, Mitchell, AM, Subashchandrabose, S. The inner membrane protein YhiM links copper and CpxAR envelope stress responses in uropathogenic E. coli. mBio. 2024;15 (4):e0352223. doi: 10.1128/mbio.03522-23. PubMed PMID:38470052 PubMed Central PMC11005409.
3. Rai, AK, Sawasato, K, Bennett, HC, Kozlova, A, Sparagna, GC, Bogdanov, M et al.. Genetic evidence for functional diversification of gram-negative intermembrane phospholipid transporters. bioRxiv. 2024; :. doi: 10.1101/2023.06.21.545913. PubMed PMID:37745482 PubMed Central PMC10515749.
4. Morris, KN, Mitchell, AM. Phosphatidylglycerol Is the Lipid Donor for Synthesis of Phospholipid-Linked Enterobacterial Common Antigen. J Bacteriol. 2023;205 (1):e0040322. doi: 10.1128/jb.00403-22. PubMed PMID:36622229 PubMed Central PMC9879101.
5. Bautista, DE, Carr, JF, Mitchell, AM. Suppressor Mutants: History and Today's Applications. EcoSal Plus. 2021;9 (2):eESP00372020. doi: 10.1128/ecosalplus.ESP-0037-2020. PubMed PMID:34910591 PubMed Central PMC9008745.
6. Rai, AK, Carr, JF, Bautista, DE, Wang, W, Mitchell, AM. ElyC and Cyclic Enterobacterial Common Antigen Regulate Synthesis of Phosphoglyceride-Linked Enterobacterial Common Antigen. mBio. 2021;12 (6):e0284621. doi: 10.1128/mBio.02846-21. PubMed PMID:34809459 PubMed Central PMC8609368.
7. Grimm, J, Shi, H, Wang, W, Mitchell, AM, Wingreen, NS, Huang, KC et al.. The inner membrane protein YhdP modulates the rate of anterograde phospholipid flow in Escherichia coli. Proc Natl Acad Sci U S A. 2020;117 (43):26907-26914. doi: 10.1073/pnas.2015556117. PubMed PMID:33046656 PubMed Central PMC7604412.
8. Rai, AK, Mitchell, AM. Enterobacterial Common Antigen: Synthesis and Function of an Enigmatic Molecule. mBio. 2020;11 (4):. doi: 10.1128/mBio.01914-20. PubMed PMID:32788387 PubMed Central PMC7439462.
9. Hart, EM, Mitchell, AM, Konovalova, A, Grabowicz, M, Sheng, J, Han, X et al.. A small-molecule inhibitor of BamA impervious to efflux and the outer membrane permeability barrier. Proc Natl Acad Sci U S A. 2019;116 (43):21748-21757. doi: 10.1073/pnas.1912345116. PubMed PMID:31591200 PubMed Central PMC6815139.
10. Mitchell, AM, Silhavy, TJ. Envelope stress responses: balancing damage repair and toxicity. Nat Rev Microbiol. 2019;17 (7):417-428. doi: 10.1038/s41579-019-0199-0. PubMed PMID:31150012 PubMed Central PMC6596312.