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Abstract While antibiotic resistance poses a threat from both Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB), GNB pose a more imminent public health hazard globally. GNB are a threat to growing antibiotic resistance because of the complex makeup of the membrane. The AcrAB-TolC efflux pump is a known resistance mechanism ofEscherichia coli (E. coli)cells. This study utilized molecular dynamics modeling to visualize some of the changes occurring at a molecular level when airborne bacteria are exposed to stress and antibiotics. This study was conducted to build upon previous experimental research showing that there is an increase in antibiotic resistance and efflux pump activity when exposed to aerosolization. AcrB and AcrAB-TolC proteins were simulated under standard and increased pressure to compare the effect of aerosolization on the binding to the three different antibiotics (puromycin (PUY), ampicillin (AMP) and sulfamethoxazole-trimethoprim (SXT)) to the AcrB binding site. Analysis such as root-mean-square deviation of atomic positions and root-mean-square fluctuation, the opening of TolC, and the significant molecular mechanics with generalized Born and surface area solvation (MM-GBSA) scores associated with specific ligands were recorded. Resistance in experimental data indicated a relationship between the docking scores and some ligand–protein interactions. Results showed that there was more flexibility in the proteins within simulations conducted under standard pressure for the AcrB protein and the full tripartite complex AcrAB-TolC, showing that increased pressure causes more rigidity. MM-GBSA scores, used to calculate the free energy of ligand–protein binding, did not show a significant change, but interestingly, the strongest MM-GBSA scores were for ligands that moved to another binding pocket and did not result in resistance or opening of the efflux pump. However, the ligand moved from the binding site and did not cause the opening of TolC to increase significantly, whereas PUY and AMP were bound to the binding site for the duration of all simulations. AMP ligands under increased pressure showed the largest change in opening of the TolC efflux pump and aligns with experimental data showingE. colicells had the most resistance to AMP after aerosolization. These results, in addition to other real-time changes such as OM proteins and mutations of targets within the cell, could be used to delineate and mitigate antibiotic resistance mechanisms.
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This content will become publicly available on December 1, 2026
Airborne Escherichia coli bacteria biosynthesize lipids in response to aerosolization stress
Gram-negative bacteria pose an increased threat to public health because of their ability to evade the effects of many antimicrobials with growing antibiotic resistance globally. One key component of gram-negative bacteria resistance is the functionality and the cells’ ability to repair the outer membrane (OM) which acts as a barrier for the cell to the external environment. The biosynthesis of lipids, particularly lipopolysaccharides, or lipooligosaccharides (LPS/LOS) is essential for OM repair. Here we show the phenotypic and genotypic changes of Escherichia coli MG1655 (E. coli) before and after exposure to short-term aerosolization, 5 min, and long-term indoor aerosolization, 30 min. Short-term aerosolization samples exhibited major damages to the OM and resulted in the elongation of the cells. Long-term aerosolization seemed to lead to cell lysis and aggregation of cell material. Disintegrated OM rendered some of the elongated cells susceptible to cytoplasmic leakage and other damages. Further analysis of the repairs the E. coli cells seemed to enact after short-term aerosolization revealed that the repair molecules were likely lipid-containing droplets that perfectly countered the air pressure impacting the E. coli cells. If lipid biosynthesis to counter the pressure is inhibited in bacteria that are exposed to environmental conditions with high air velocity, the cells would lyse or be exposed to more toxins and thus become more susceptible to antimicrobial treatments. This article is the first to show lipid behavior in response to aerosolization stress in airborne bacteria both genotypically and phenotypically. Understanding the relationship between environmental conditions in ventilated spaces, lipid biosynthesis, and cellular responses is crucial for developing effective strategies to combat bacterial infections and antibiotic resistance. By elucidating the repair mechanisms initiated by E. coli in response to aerosolization, this study contributes to the broader understanding of bacterial adaptation and vulnerability under specific environmental pressures. These insights may pave the way for novel therapeutic approaches that target lipid biosynthesis pathways and exploit vulnerabilities in bacterial defenses, ultimately improving treatment outcomes
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- Award ID(s):
- 2034048
- PAR ID:
- 10574907
- Publisher / Repository:
- Scientific Reports
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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