Biology subjects

Lee, T. C.

Publications and source records attributed to Lee, T. C..

4 recordsLinked to original sources

bioRxiv2026

In vitro exposure to non-antipseudomonal antibiotics (NAPA) induces Pseudomonas aeruginosa resistance to antipseudomonal antibiotics (APA)

BackgroundPseudomonas aeruginosa readily evolves antimicrobial resistance through regulatory plasticity and stress-adaptive pathways. Clinically, antibiotics lacking intrinsic antipseudomonal activity are often favored with the assumption that they avoid selective pressure on P. aeruginosa. Whether subinhibitory exposure to such "non-antipseudomonal antibiotics" (NAPA) can nevertheless select for canonical resistance pathways remains incompletely defined. Methods: Three P. aeruginosa strains (ATCC 27853 and two bloodstream isolates) were serially passaged over 14 days in the presence of ertapenem, ceftriaxone, or moxifloxacin at one-third the baseline minimum inhibitory concentration (MIC). MICs for antipseudomonal antibiotics (meropenem, ceftazidime, ciprofloxacin) were measured at serial time points and after a 3-day antibiotic-free recovery (day 14). Whole-genome sequencing was performed longitudinally to identify mutations. ResultsNAPA exposure led to reproducible elevations in antipseudomonal MICs: ertapenem triggered up to a 29-fold increase in meropenem MIC, ceftriaxone up to a 31-fold rise in ceftazidime MIC, and moxifloxacin up to a 12-fold increase in ciprofloxacin MIC. Elevated MICs persisted on day 14 despite absence of further antibiotic pressure. Genomic analysis revealed convergent evolution of mutations in efflux regulator genes (nfxB, nalC, nalD, amrR) and the {beta}-lactamase-regulating gene dacB, emerging during periods of MIC escalation and mapping to regulatory pathways governing efflux and AmpC expression. ConclusionSubinhibitory exposure to antibiotics without intrinsic antipseudomonal activity reproducibly selected for heritable multidrug-resistant phenotypes in P. aeruginosa. Resistance arose through convergent evolution in regulatory genes classically associated with direct antipseudomonal antibiotic pressure, demonstrating that resistance architectures can be selected independent of target engagement and underscoring the inevitability of collateral resistance under antibiotic stress. ImportancePseudomonas aeruginosa is a major cause of hospital-acquired infections and is well known for its ability to develop antibiotic resistance. Clinicians often assume that antibiotics without activity against P. aeruginosa do not meaningfully influence its resistance behavior and are therefore safe choices when this organism is not the primary target. Our study challenges this assumption. We show that low-level exposure to such antibiotics is associated with increased resistance to key antipseudomonal drugs, even after the initial antibiotic exposure ends. Rather than arising from a single stable genetic change, resistance was accompanied by shifting genetic alterations in regulatory pathways that control drug efflux and {beta}-lactamase expression. These findings highlight how antibiotic exposure can broaden the evolutionary pathways available for resistance in unintended pathogens. Recognizing these indirect and population-level effects of antibiotic use may help inform more cautious antimicrobial prescribing strategies in clinical settings.

microbiology↗

bioRxiv2025

Optogenetic construction of de novo integrin-adhesion complexes reveals role for biocondensation in adhesion nucleation

Integrin-adhesion complexes (IACs) form spontaneously in cells on extracellular matrix substrates, allowing them to sense matrix composition and transduce force. However, IACs often do not form uniformly across a cell, which begs the question: What is required to nucleate an adhesion, and what factors enable the stabilization of an IAC once it has formed? Many factors have been suggested to promote formation and the subsequent stabilization of IACs. It is difficult to explicitly test these factors in vivo as IACs undergo constant remodeling. Here, we employ optogenetics to explicitly test the ability of talin in different activity and phase states to nucleate and stabilize IACs in regions where none are present. We find that fusion of intrinsically disordered regions directly to talin enhances its adhesion nucleation potential and allows new adhesions to be produced in response to optogenetic talin clustering. Similarly, expression of factors previously shown to enhance biocondensation in vitro, such as paxillin, the paxillin N-terminus, or unfolding of talin, allows for adhesion nucleation and biocondensation of talin. We show that these biocondensates of talin can cluster and activate integrins even in the absence of extracellular matrix. By applying optogenetic activation to regions of the cell with or without ventral actomyosin, we demonstrate actomyosin engagement promotes the formation and stability of adhesions. These results are corroborated by theoretical modelling which shows that phase separation of talin is enhanced by differential clutch formation in the presence of actomyosin thus enabling peripheral adhesion formation and stability. This work establishes a model in which increased cooperativity of talin enables IAC nucleation through talin biocondensation, which clusters and activates integrins. In addition to these findings, we generate multiple optogenetic tools that enable local nucleation or enhancement of IACs. HighlightsO_LIOptogenetic tools mediating talin biocondensation can locally induce focal adhesion formation C_LIO_LIPaxillin LD domains enable biocondensation of talin C_LIO_LIBiocondensation of talin enables IAC formation C_LIO_LIPhase separation of talin can activate integrins independently of ECM C_LIO_LIComputational model reconciles spatial variance in LLPS and IAC formation. C_LI

cell biology↗

bioRxiv2022

Multi-scale modelling of shear stress on the syncytiotrophoblast: Could maternal blood flow impact placental function across gestation?

The surface of the placenta is lined by a single multinucleated cell, the syncytiotrophoblast, which forms a functional barrier between maternal and fetal blood in pregnancy. The placenta plays a critical role in healthy fetal development and over the course of pregnancy forms a complex branching tree-like structure which bathes in maternal blood and serves a vital exchange function. It has been suggested that the structure of the placenta may evolve, in part, under the influence of the shear stress exerted by maternal blood flow over its surface, with the syncytiotrophoblast having a role in mechanosensing. However, data describing the mechano-sensitive nature of this cell, particularly in early gestation, is lacking. In this study we show that the syncytiotrophoblast expresses six proteins that have been related to shear sensing, and this expression is higher in the first trimester than at term. This suggests shear on the sycytiotrophoblast as an important factor influencing placental morphogenesis early in pregnancy. We then predict shear stress felt by the syncytiotrophoblast in first trimester and term placental tissue using a combination of porous medium modelling and explicit simulations of blood flow in realistic geometries derived from microCT imaging. Our models predict that typical shear stress on first-trimester tissue is higher than at term, supporting the feasibility of this mechanical stimulus as an important driver of healthy placental development.

bioengineering↗

bioRxiv2022

Defining Predictors of Successful Early Career to Independent Funding Conversion Among Surgeon-Scientists

IntroductionThe National Institutes of Health (NIH) provides research funding to scientists at different stages of their career through a range of grant awards. Early-stage researchers are eligible for mentored Career Development (K) awards, to aid in the transition to independent NIH funding. Factors such as education, subspecialty, and time to funding have been studied as predictors of obtaining independent awards in nonsurgical specialties. However, in surgery, the importance of these factors has yet to be clearly elucidated. We aim to identify predictors of K to independent award conversion among surgeon-scientists to understand how to better support early-stage researchers transitioning to independent careers. Materials and MethodsIn July 2020, the NIH Research Portfolio Online Reporting Tools database was queried for individuals affiliated with surgery departments who received NIH Career Development Awards (between 2000 and 2020). The following factors were analyzed: publications, institution, degrees, year of completion of training, and gender. ResultsBetween 2000 and 2020, 228 surgeons received K Awards, of which 44% transitioned to independent funding. On average, surgeons received a K award 4.0 years after completing fellowship training and an independent award 5.4 years after receiving a K grant. The time to receiving a K award was predictive of successfully achieving independent funding, and those with independent funding had a significantly greater number of publications per year of their K-award. ConclusionSurgeons successful in transitioning to independent NIH awards do so approximately 9 years after finishing fellowship. Publication track record is the main factor associated with successful conversion from a K award. Surgery departments should emphasize manuscript productivity and develop strategies to minimize time to independent funding to help K-awardees begin independent research careers.

scientific communication and education↗