Biology subjects

Mohiuddin, S. G.

Publications and source records attributed to Mohiuddin, S. G..

6 recordsLinked to original sources

bioRxiv2026

Glycerol-Driven Energy and Proteostasis Underpin Antibiotic Tolerance in Escherichia coli

Bacterial persisters are frequently described as metabolically dormant, yet the endogenous metabolic programs that sustain survival during prolonged nutrient limitation remain poorly understood. Here, using stationary-phase Escherichia coli as a model of antibiotic tolerance, we combine proteomics, genetics, metabolic phenotyping, and single-cell imaging to define a metabolic framework underlying persistence. Perturbation of tricarboxylic acid cycle function broadly reprogrammed stationary-phase physiology, suppressing lipid and glycerol metabolism, altering energy homeostasis and proteostasis, and reducing antibiotic tolerance. Systems-level analyses identified phospholipid-derived glycerol catabolism as a central metabolic node linking endogenous carbon recycling to persistence. Genetic disruption of glycerol utilization impaired proton motive force homeostasis, reduced formation of large polar protein aggregates, altered division-associated remodeling, and sensitized cells to antibiotic-induced lysis. Functional metabolic assays further revealed that persisters retain a selective capacity to utilize glycerol for rapid proton motive force restoration without growth resumption. Together, our findings support a model in which stationary-phase persisters are not metabolically inert but sustained through endogenous metabolic rewiring that coordinates energy maintenance, proteostasis, and antibiotic tolerance.

microbiology↗

bioRxiv2024

The Diverse Phenotypic and Mutational Landscape Induced by Fluoroquinolone Treatment

Despite extensive research on antibiotic resistance, the potential effects of antibiotic treatments on bacterial tolerance and resistance remain a significant concern. Although bacterial cells adopt a variety of mutational strategies to resist unfavorable circumstances, it is still unclear how antibiotic tolerance and resistance mechanisms affect bacterial fitness characteristics and whether evolved mutants exhibit similar properties across different cell populations subjected to the same conditions. Here, we used Escherichia coli, a fluoroquinolone antibiotic (ofloxacin), and adaptive laboratory evolutionary experiments to demonstrate that ofloxacin tolerance and resistance can evolve independently across different cell populations exposed to identical conditions. Fitness attributes, such as lag score, doubling time, competition score, and other metabolic features, were variably affected by antibiotic tolerance and resistance mechanisms. However, we did not observe strong and apparent correlations between fitness trade-offs and antibiotic tolerance and resistance. While our whole-genome sequencing identified some shared mutations, such as single nucleotide polymorphisms in the icd gene (a crucial citric acid cycle gene), evolved cell populations exhibited diverse genetic mutations without a clear pattern of a conserved evolutionary pathway. Our study also identifies unique phenotypes, such as those displaying significantly lower minimum inhibitory concentration levels compared to the parental strain yet showing remarkably high tolerance to the same antibiotic. Altogether, our study, examining the phenotypic and mutational landscapes of fluoroquinolone-induced strains, contributes to our understanding of complex bacterial adaptation mechanisms.

microbiology↗

bioRxiv2024

Unraveling CRP/cAMP-Mediated Metabolic Regulation In Escherichia coli Persister Cells

A substantial gap persists in our comprehension of how bacterial metabolism undergoes rewiring during the transition to a persistent state. Also, it remains unclear which metabolic mechanisms become indispensable for persister cell survival. To address these questions, we directed our efforts towards persister cells in Escherichia coli that emerge during the late stationary phase. These cells have been recognized for their exceptional resilience and are commonly believed to be in a dormant state. Our results indicate that the global metabolic regulator Crp/cAMP redirects the metabolism of these antibiotic-tolerant cells from anabolism to oxidative phosphorylation. Although our data demonstrates that persisters exhibit a reduced metabolic rate compared to rapidly growing exponential-phase cells, their survival still relies on energy metabolism. Extensive genomic-level analyses of metabolomics, proteomics, and single-gene deletions consistently highlight the critical role of energy metabolism, specifically the tricarboxylic acid (TCA) cycle, electron transport chain (ETC), and ATP synthase, in sustaining persister levels within cell populations. Altogether, this study provides much-needed clarification regarding the role of energy metabolism in antibiotic tolerance and highlights the importance of using a multipronged approach at the genomic level to obtain a broader picture of the metabolic state of persister cells.

microbiology↗

bioRxiv2022

PROTON MOTIVE FORCE INHIBITORS ARE DETRIMENTAL TO METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS PERSISTER CELLS

Methicillin-resistant Staphylococcus aureus (MRSA) strains are resistant to conventional antibiotics. These pathogens can form persister cells, which are transiently tolerant to bactericidal antibiotics, making them extremely dangerous. Previous studies have shown the effectiveness of proton motive force (PMF) inhibitors at killing bacterial cells; however, whether these agents can launch a new treatment strategy to eliminate persister cells mandates further investigation. Here, using known PMF inhibitors and two different MRSA isolates, we showed that antipersister potency of PMF inhibitors seemed to correlate with their ability to disrupt PMF and permeabilize cell membranes. By screening a small chemical library to verify this correlation, we identified a subset of chemicals (including nordihydroguaiaretic acid, gossypol, trifluoperazine, and amitriptyline) that strongly disrupted PMF in MRSA cells by dissipating either the transmembrane electric potential ({Delta}{Psi}) or the proton gradient ({Delta}pH). These drugs robustly permeabilized cell membranes and reduced persister levels below the limit of detection. Overall, our study further highlights the importance of cellular PMF as a target for designing new antipersister therapeutics.

microbiology↗

bioRxiv2021

LON DELETION IMPAIRS PERSISTER CELL RESUSCITATION IN ESCHERICHIA COLI

Bacterial persisters are non-growing cells that are highly tolerant to bactericidal antibiotics. However, this tolerance is reversible and not mediated by heritable genetic changes. Lon, an ATP-dependent protease, has repeatedly been shown to play a critical role in fluoroquinolone persistence. Although lon deletion ({Delta}lon) is thought to kill persister cells via accumulation of the cell division inhibitor protein SulA, the exact mechanism underlying this phenomenon has yet to be elucidated. Here, we show that Lon is an important regulatory protein for the resuscitation of the fluoroquinolone persisters in Escherichia coli, and lon deletion impairs the ability of persister cells to form colonies during recovery, without killing these cells, through a sulA- and ftsZ-dependent mechanism. Notably, this observed non-culturable state of antibiotic-tolerant {Delta}lon cells is transient, as environmental conditions, such as starvation, can restore their culturability. Our data further indicate that starvation-induced SulA degradation or expression of Lon during recovery facilitates Z-ring formation in {Delta}lon persisters. Calculating the ratio of the cell length (L in {micro}m) to the number of Z-rings (Z) for each ofloxacin-treated intact cell analyzed has revealed a strong correlation between persister resuscitation and calculated L/Z values, which represents a potential biomarker for {Delta}lon persisters that are transitioning to the normal cell state under the conditions studied here.

microbiology↗

bioRxiv2019

Therapeutically Exploring Persister Metabolism In Bacteria

Bacterial persisters are rare phenotypic variants that are temporarily tolerant to high concentrations of antibiotics. We have previously discovered that persisters are mostly derived from stationary-phase cells with high redox activities that are maintained by endogenous protein and RNA degradation. This intracellular degradation resulted in self-inflicted damage that transiently repressed the cellular functions targeted by antibiotics. Leveraging this knowledge, we developed an assay integrating a degradable fluorescent protein system and a small library, containing FDA-approved drugs and antibiotics, to detect chemicals that target persister metabolism. We identified several metabolic inhibitors, including anti-psychotic drugs, that can reduce Escherichia coli persistence. These chemical inhibitors also reduce Pseudomonas aeruginosa persistence, potentially verifying the existence of similar mechanisms in a medically relevant organism.

microbiology↗