Digital Commons Network^™

Blinking Phase-Change Nanocapsules Enable Background-Free Ultrasound Imaging, Alexander S. Hannah, Geoffrey P. Luke, Stanislav Y. Emelianov

Dartmouth Scholarship

Microbubbles are widely used as contrast agents to improve the diagnostic capability of conventional, highly speckled, low-contrast ultrasound imaging. However, while microbubbles can be used for molecular imaging, these agents are limited to the vascular space due to their large size (> 1 μm). Smaller microbubbles are desired but their ultrasound visualization is limited due to lower echogenicity or higher resonant frequencies. Here we present nanometer scale, phase changing, blinking nanocapsules (BLInCs), which can be repeatedly optically triggered to provide transient contrast and enable background-free ultrasound imaging. In response to irradiation by near-infrared laser pulses, the BLInCs undergo cycles of …

Individual Differences In Response Of Dorsomedial Prefrontal Cortex Predict Daily Social Behavior, Katherine E. Powers, Robert S. Chavez, Todd F. Heatherton

Dartmouth Scholarship

The capacity to accurately infer the thoughts and intentions of other people is critical for effective social interaction, and neural activity in dorsomedial prefrontal cortex (dmPFC) has long been linked with the extent to which people engage in mental state attribution. In this study, we combined functional neuroimaging and experience sampling methodologies to test the predictive value of this neural response for daily social behaviors. We found that individuals who displayed greater activity in dmPFC when viewing social scenes spent more time around other people on a daily basis. These findings suggest a specific role for the neural mechanisms that …

Secretion Of Rhoptry And Dense Granule Effector Proteins By Nonreplicating Toxoplasma Gondii Uracil Auxotrophs Controls The Development Of Antitumor Immunity, Barbara A. Fox, Kiah L. Sanders, Leah M. Rommereim, Rebekah B. Guevara, David J. Bzik

Dartmouth Scholarship

Nonreplicating type I uracil auxotrophic mutants of Toxoplasma gondii possess a potent ability to activate therapeutic immunity to established solid tumors by reversing immune suppression in the tumor microenvironment. Here we engineered targeted deletions of parasite secreted effector proteins using a genetically tractable Δku80 vaccine strain to show that the secretion of specific rhoptry (ROP) and dense granule (GRA) proteins by uracil auxotrophic mutants of T. gondii in conjunction with host cell invasion activates antitumor immunity through host responses involving CD8α⁺ dendritic cells, the IL-12/interferon-gamma (IFN-γ) T_H1 axis, as well as CD4⁺ and CD8 …

Patient‐Defined Goals For The Treatment Of Severe Aortic Stenosis: A Qualitative Analysis, Megan Coylewright, Roseanne Palmer, Elizabeth S. O'Neill, John F. Robb, Terri Fried

Dartmouth Scholarship

Patients with severe aortic stenosis (AS) at high risk for aortic valve replacement are a unique population with multiple treatment options, including medical therapy, surgical aortic valve replacement and transcatheter aortic valve replacement (TAVR). Traditionally, in elderly populations, goals of treatment may favour quality of life over survival. Professional guidelines recommend that clinicians engage patients in shared decision making, a process that may lead to decisions more aligned with patient-defined goals of care. Goals of care for high-risk patients with AS are not well defined in the literature, and patient-reported barriers to shared decision making highlight the need for explicit …

Protocol For The Seed-Trial: Supported Employment And Preventing Early Disability, Vigdis Sveinsdottir, Torill Tveito, Gary R. Bond, Astrid L. Grasdal, Stein A. Lie, Silje E. Reme

Dartmouth Scholarship

Early withdrawal or exclusion from the labor market leads to significant personal and societal costs. In Norway, the increasing numbers of young adults receiving disability pension is a growing problem. While a large body of research demonstrates positive effects of Supported Employment (SE) in patients with severe mental illness, no studies have yet investigated the effectiveness of SE in young adults with a range of social and health conditions who are receiving benefits.

The Intrinsic Eddington Ratio Distribution Of Active Galactic Nuclei In Star-Forming Galaxies From The Sloan Digital Sky Survey, Mackenzie L. Jones, Ryan C. Hickox, Christine S. Black, Kevin N. Hainline, Michael A. Dipompeo, Andy D. Goulding

Dartmouth Scholarship

An important question in extragalactic astronomy concerns the distribution of black hole accretion rates of active galactic nuclei (AGNs). Based on observations at X-ray wavelengths, the observed Eddington ratio distribution appears as a power law, while optical studies have often yielded a lognormal distribution. There is increasing evidence that these observed discrepancies may be due to contamination by star formation and other selection effects. Using a sample of galaxies from the Sloan Digital Sky Survey Data Release 7, we test whether or not an intrinsic Eddington ratio distribution that takes the form of a Schechter function is consistent with previous …

A Face Versus Non-Face Context Influences Amygdala Responses To Masked Fearful Eye Whites, M. Justin Kim, Kimberly M. Solomon, Maital Neta, F. Caroline Davis, Jonathan A. Oler, Emily C. Mazzulla, Paul J. Whalen

Dartmouth Scholarship

The structure of the mask stimulus is crucial in backward masking studies and we recently demonstrated such an effect when masking faces. Specifically, we showed that activity of the amygdala is increased to fearful facial expressions masked with neutral faces and decreased to fearful expressions masked with a pattern mask—but critically both masked conditions discriminated fearful expressions from happy expressions. Given this finding, we sought to test whether masked fearful eye whites would produce a similar profile of amygdala response in a face vs non-face context. During functional magnetic resonance imaging scanning sessions, 30 participants viewed fearful or happy eye …

Dynamical Decoupling Sequences For Multi-Qubit Dephasing Suppression And Long-Time Quantum Memory, Gerardo A. Paz-Silva, Seung-Woo Lee, Todd J. Green, Lorenza Viola

Dartmouth Scholarship

We consider a class of multi-qubit dephasing models that combine classical noise sources and linear coupling to a bosonic environment, and are controlled by arbitrary sequences of dynamical decoupling pulses. Building on a general transfer filter-function framework for open-loop control, we provide an exact representation of the controlled dynamics for arbitrary stationary non-Gaussian classical and quantum noise statistics, with analytical expressions emerging when all dephasing sources are Gaussian. This exact characterization is used to establish two main results. First, we construct multi-qubit sequences that ensure maximum high-order error suppression in both the time and frequency domain and that can be …

A Heavy Metal P-Type Atpase Oshma4 Prevents Copper Accumulation In Rice Grain, Xin-Yuan Huang, Fenglin Deng, Naoki Yamaji, Shannon R.M. Pinson, Miho Fujii-Kashino, John Danku, Alex Douglas, Mary Lou Guerinot, David Salt, Jian Feng Ma

Dartmouth Scholarship

Rice is a major source of calories and mineral nutrients for over half the world's human population. However, little is known in rice about the genetic basis of variation in accumulation of copper (Cu), an essential but potentially toxic nutrient. Here we identify OsHMA4 as the likely causal gene of a quantitative trait locus controlling Cu accumulation in rice grain. We provide evidence that OsHMA4 functions to sequester Cu into root vacuoles, limiting Cu accumulation in the grain. The difference in grain Cu accumulation is most likely attributed to a single amino acid substitution that leads to different OsHMA4 transport …

Design Of Nanoparticle-Based Carriers For Targeted Drug Delivery, Xiaojiao Yu, Ian Trase, Muqing Ren, Kayla Duval, Xing Guo, Zi Chen

Dartmouth Scholarship

Nanoparticles have shown promise as both drug delivery vehicles and direct antitumor systems, but they must be properly designed in order to maximize efficacy. Computational modeling is often used both to design new nanoparticles and to better understand existing ones. Modeled processes include the release of drugs at the tumor site and the physical interaction between the nanoparticle and cancer cells. In this paper, we provide an overview of three different targeted drug delivery methods (passive targeting, active targeting, and physical targeting) and compare methods of action, advantages, limitations, and the current stages of research. For the most commonly used …

Methylation Of The Leukocyte Glucocorticoid Receptor Gene Promoter In Adults: Associations With Early Adversity And Depressive, Anxiety And Substance-Use Disorders, A. R. Tyrka, S H. Parade, E S. Welch, K. K. Ridout, L Price, C Marsit, L Carpenter

Dartmouth Scholarship

Early adversity increases risk for developing psychopathology. Epigenetic modification of stress reactivity genes is a likely mechanism contributing to this risk. The glucocorticoid receptor (GR) gene is of particular interest because of the regulatory role of the GR in hypothalamic–pituitary–adrenal (HPA) axis function. Mounting evidence suggests that early adversity is associated with GR promoter methylation and gene expression. Few studies have examined links between GR promoter methylation and psychopathology, and findings to date have been mixed. Healthy adult participants (N = 340) who were free of psychotropic medications reported on their childhood experiences of maltreatment and parental death and desertion. …

Star Formation In Quasar Hosts And The Origin Of Radio Emission In Radio-Quiet Quasars, Nadia L. Zakamska, Kelly Lampayan, Andreea Petric, Daniel Dicken, Jenny E. Greene, Timothy M. Heckman, Ryan C. Hickox

Dartmouth Scholarship

Radio emission from radio-quiet quasars may be due to star formation in the quasar host galaxy, to a jet launched by the supermassive black hole, or to relativistic particles accelerated in a wide-angle radiatively-driven outflow. In this paper we examine whether radio emission from radio-quiet quasars is a byproduct of star formation in their hosts. To this end we use infrared spectroscopy and photometry from Spitzer and Herschel to estimate or place upper limits on star formation rates in hosts of ~300 obscured and unobscured quasars at z<1. We find that low-ionization forbidden emission lines such as [NeII] and [NeIII] are likely dominated by quasar ionization and do not provide reliable star formation diagnostics in quasar hosts, while PAH emission features may be suppressed due to the destruction of PAH molecules by the quasar radiation field. While the bolometric luminosities of our sources are dominated by the quasars, the 160 micron fluxes are likely dominated by star formation, but they too should be used with caution. We estimate median star formation rates to be 6-29 Msun/year, with obscured quasars at the high end of this range. This star formation rate is insufficient to explain the observed radio emission from quasars by an order of magnitude, with log(L_radio, observed/L_radio, SF)=0.6-1.3 depending on quasar type and star formation estimator. Although radio-quiet quasars in our sample lie close to the 8-1000 micron infrared / radio correlation characteristic of the star-forming galaxies, both their infrared emission and their radio emission are dominated by the quasar activity, not by the host galaxy.

Population Properties Of Brown Dwarf Analogs To Exoplanets, Jacqueline K. Faherty, Adric R. Riedel, Kelle L. Cruz, Jonathan Gagne, Joseph C. Filippazzo, Erini Lambrides, Haley Fica, Alycia Weinberger, John R. Thorstensen

Dartmouth Scholarship

We present a kinematic analysis of 152 low surface gravity M7-L8 dwarfs by adding 18 new parallaxes (including 10 for comparative field objects), 38 new radial velocities, and 19 new proper motions. We also add low- or moderate-resolution near-infrared spectra for 43 sources confirming their low surface gravity features. Among the full sample, we find 39 objects to be high-likelihood or new bona fide members of nearby moving groups, 92 objects to be ambiguous members and 21 objects that are non-members. Using this age-calibrated sample, we investigate trends in gravity classification, photometric color, absolute magnitude, color–magnitude, luminosity, and effective temperature. …

Physical Activity And Risk Of Breast Cancer, Colon Cancer, Diabetes, Ischemic Heart Disease, And Ischemic Stroke Events: Systematic Review And Dose-Response Meta-Analysis For The Global Burden Of Disease Study 2013, Hmwe H. Kyu, Victoria F. Bachman, Lily T. Alexander, John E. Mumford, Ashkan Afshin, Kara Estep, J. Lennert Veerman, Kristen Delwiche

Dartmouth Scholarship

Objective: To quantify the dose-response associations between total physical activity and risk of breast cancer, colon cancer, diabetes, ischemic heart disease, and ischemic stroke events.

A New Method For Ecoacoustics? Toward The Extraction And Evaluation Of Ecologically-Meaningful Soundscape Components Using Sparse Coding Methods, Alice Eldridge, Michael Casey, Paola Moscoso, Mika Peck

Dartmouth Scholarship

Passive acoustic monitoring is emerging as a promising non-invasive proxy for ecological complexity with potential as a tool for remote assessment and monitoring (Sueur & Farina, 2015). Rather than attempting to recognise species-specific calls, either manually or automatically, there is a growing interest in evaluating the global acoustic environment. Positioned within the conceptual framework of ecoacoustics, a growing number of indices have been proposed which aim to capture community- level dynamics by (e.g., Pieretti, Farina & Morri, 2011; Farina, 2014; Sueur et al.,2008b) by providing statistical summaries of the frequency or time domain signal. Although promising, the ecological relevance and …

Quantum Random Number Generation Using A Quanta Image Sensor, Emna Amri, Yacine Felk, Damien Stucki, Jiaju Ma, Eric Fossum

Dartmouth Scholarship

A new quantum random number generation method is proposed. The method is based on the randomness of the photon emission process and the single photon counting capability of the Quanta Image Sensor (QIS). It has the potential to generate high-quality random numbers with remarkable data output rate. In this paper, the principle of photon statistics and theory of entropy are discussed. Sample data were collected with QIS jot device, and its randomness quality was analyzed. The randomness assessment method and results are discussed.

Ethics In Community-Based Research With Vulnerable Children: Perspectives From Rwanda, Theresa Betancourt, Mary C. Smith Fawzi, Anne Stevenson, Fredrick Kanyanganzi, Catherine Kirk, Lauren Ng, Christina Mushashi, Justin I. Bizimana, William Beardslee, Guiseppe Raviola, Stephanie Smith, Yvonne Kayiteshonga, Agnes Binagwaho

Dartmouth Scholarship

A “risk of harm” protocol to identify youth in need of immediate emergency assistance in a study on mental health and HIV in Rwanda among 680 youth ages 10–17 is described. Cases are presented that describe the experience in using this protocol to ensure safety of participants, with ethical and logistical challenges considered. Among the population of the study, 3.2% were deemed "risk of harm.” The most prevalent presenting problem was non-fatal suicidal behavior (91% of risk of harm cases), with 36% having a history of a reported previous attempt. Challenges included: acute food insecurity/significant poverty; lack of support/adequate supervision …

Demo: Wanda, Securely Introducing Mobile Devices, Timothy J. Pierson, Xiaohui Liang, Ronald Peterson, David Kotz

Dartmouth Scholarship

Nearly every setting is increasingly populated with wireless and mobile devices – whether appliances in a home, medical devices in a health clinic, sensors in an industrial setting, or devices in an office or school. There are three fundamental operations when bringing a new device into any of these settings: (1) to configure the device to join the wireless local-area network, (2) to partner the device with other nearby devices so they can work together, and (3) to configure the device so it connects to the relevant individual or organizational account in the cloud. The challenge is to accomplish all …

Speculating The Subject Of Money: Georg Simmel On Human Value, Devin Singh

Dartmouth Scholarship

This article initiates an inquiry into the sources and frameworks of value used to denote human subjects in modernity. In particular, I consider the conflation of monetary, legal, and theological registers employed to demarcate human worth. Drawing on Simmel’s speculative genealogy of the money equivalent of human values, I consider the spectrum of ascriptions from specifically quantified to infinite human value. I suggest that predications of infinite human value require and imply quantified—and specifically monetary-economic—human value. Cost and worth, economically and legally defined, provide a foundation for subsequent eternal projections in a theological imaginary. This calls into question the interventionist …

Microrna Mir-155 Is Necessary For Efficient Gammaherpesvirus Reactivation From Latency, But Not For Establishment Of Latency, Rebecca L. Crepeau, Peisheng Zhang, Edward J. Usherwood

Dartmouth Scholarship

MicroRNA-155 (miR-155) has been shown to play significant roles in the immune response, including in the formation of germinal centers (GC) and the development and maturation of T follicular helper (Tfh) cells. There is in vitro evidence to support a critical role for cellular miR-155 and viral miR-155 homologs in the establishment of gammaherpesvirus latency in B cells. We sought to determine the contribution of miR-155 to the establishment and maintenance of latency in vivousing murine gammaherpesvirus (MHV-68) infection. MHV-68-infected mice deficient in miR-155 exhibited decreases in GC B cells and Tfh cells. However, the frequencies of spleen cells …

Cyclic Di-Gmp-Regulated Periplasmic Proteolysis Of A Pseudomonas Aeruginosa Type Vb Secretion System Substrate, Richard B. Cooley, T. Jarrod Smith, Wilfred Leung, Valerie Tierney, Bradley Borlee, George A. O'Toole, Holger Sondermann

Dartmouth Scholarship

We previously identified a second-messenger-regulated signaling system in the environmental bacterium Pseudomonas fluorescens which controls biofilm formation in response to levels of environmental inorganic phosphate. This system contains the transmembrane cyclic di-GMP (c-di-GMP) receptor LapD and the periplasmic protease LapG. LapD regulates LapG and controls the ability of this protease to process a large cell surface adhesin protein, LapA. While LapDG orthologs can be identified in diverse

Alcohol Discrimination And Preferences In Two Species Of Nectar-Feeding Primate, Samuel R. Gochman, Michael B. Brown, Nathaniel J. Dominy

Dartmouth Scholarship

Recent reports suggest that dietary ethanol, or alcohol, is a supplemental source of calories for some primates. For example, slow lorises (Nycticebus coucang) consume fermented nectars with a mean alcohol concentration of 0.6% (range: 0.0–3.8%). A similar behaviour is hypothesized for aye-ayes (Daubentonia madagascariensis) based on a single point mutation (A294V) in the gene that encodes alcohol dehydrogenase class IV (ADH4), the first enzyme to catabolize alcohol during digestion. The mutation increases catalytic efficiency 40-fold and may confer a selective advantage to aye-ayes that consume the nectar of Ravenala madagascariensis. It is uncertain, however, whether alcohol exists in this nectar …

The Brain Imaging Data Structure, A Format For Organizing And Describing Outputs Of Neuroimaging Experiments, Krzysztof Gorgolewski, Tibor Auer, Vince Calhoun, R Cameron Craddock, Samir Das, Eugene Duff, Guillaume Flandin, Tristan Glatard, Yaroslav Halchenko

Dartmouth Scholarship

The development of magnetic resonance imaging (MRI) techniques has defined modern neuroimaging. Since its inception, tens of thousands of studies using techniques such as functional MRI and diffusion weighted imaging have allowed for the non-invasive study of the brain. Despite the fact that MRI is routinely used to obtain data for neuroscience research, there has been no widely adopted standard for organizing and describing the data collected in an imaging experiment. This renders sharing and reusing data (within or between labs) difficult if not impossible and unnecessarily complicates the application of automatic pipelines and quality assurance protocols. To solve this …

Consistency Of Hemoglobin A1c Testing And Cardiovascular Outcomes In Medicare Patients With Diabetes, Philip P. Goodney, Karina A. Newhall, Kimon Bekelis, Daniel Gottlieb, Richard Comi, Sushela Chaudrain, Adrienne E. Faerber, Todd A. Mackenzie, Jonathan S. Skinner

Dartmouth Scholarship

Background:

Annual hemoglobin A1c testing is recommended for patients with diabetes mellitus. However, it is unknown how consistently patients with diabetes mellitus receive hemoglobin A1c testing over time, or whether testing consistency is associated with adverse cardiovascular outcomes.

Methods and Results:

We identified 1 574 415 Medicare patients (2002–2012) with diabetes mellitus over the age of 65. We followed each patient for a minimum of 3 years to determine their consistency in hemoglobin A1C testing, using 3 categories: low (testing in 0 or 1 of 3 years), medium (testing in 2 of 3 years), and high (testing in all 3 …

Female Chromosome X Mosaicism Is Age-Related And Preferentially Affects The Inactivated X Chromosome, Mitchell J. Machiela, Weiyin Zhou, Eric Karlins, Joshua N. Sampson, Neal D. Freedman, Qi Yang, Belynda Hicks, Casey Dagnall, Christopher Hautman, Kevin B. Jacobs, Christian C. Abnet, Melinda C. Aldrich, Christopher Amos, Laufey T. Amundadottir, Alan A. Arslan, Laura E. Beane-Freeman, Sonja I. Berndt, Amanda Black, William J. Blot, Cathryn H. Bock, Paige M. Bracci, Louise A. Brinton, H Bas Bueno-De-Mesquita, Laurie Burdett, Julie E. Buring, Mary A. Butler, Federico Canzian, Tania Carreon, Kari G. Chaffee, I-Shou Chang, Nilanjan Chatterjee, Chu Chen, Constance Chen, Kexin Chen, Charles C. Chung, Linda S. Cook, Marta Crous Bou, Michael Cullen, Faith G. Davis, Immaculata De Vivo, Ti Ding, Jennifer Doherty

Dartmouth Scholarship

To investigate large structural clonal mosaicism of chromosome X, we analysed the SNP microarray intensity data of 38,303 women from cancer genome-wide association studies (20,878 cases and 17,425 controls) and detected 124 mosaic X events 4 2 Mb in 97 (0.25%) women. Here we show rates for X-chromosome mosaicism are four times higher than mean autosomal rates; X mosaic events more often include the entire chromosome and participants with X events more likely harbour autosomal mosaic events. X mosaicism frequency increases with age (0.11% in 50-year olds; 0.45% in 75-year olds), as reported for Y and autosomes. Methylation array analyses …

A Cyclic Universe Approach To Fine Tuning, Stephon Alexander, Sam Cormack, Marcelo Gleiser

Dartmouth Scholarship

We present a closed bouncing universe model where the value of coupling constants is set by the dynamics of a ghost-like dilatonic scalar field. We show that adding a periodic potential for the scalar field leads to a cyclic Friedmann universe where the values of the couplings vary randomly from one cycle to the next. While the shuffling of values for the couplings happens during the bounce, within each cycle their time-dependence remains safely within present observational bounds for physically-motivated values of the model parameters. Our model presents an alternative to solutions of the fine tuning problem based on string …

Effect Of A Ropy Exopolysaccharide-Producing Bifidobacterium Animalis Subsp. Lactis Strain Orally Administered On Dss-Induced Colitis Mice Model, Claudio Hidalgo-Cantabrana, Francesca Algieri, Alba Rodriguez-Nogales, Teresa Vezza, Pablo Martínez-Camblor

Dartmouth Scholarship

Exopolysaccharide (EPS)-producing bifidobacteria, particularly Bifidobacterium animalis subsp. lactis strains, are used in the functional food industry as promising probiotics with purported beneficial effects. We used three isogenic strains of B. animalis subsp. lactis, with different EPS producing phenotypes (mucoid-ropy and non-ropy), in order to determine their capability to survive the murine gastrointestinal tract transit, as well as to evaluate their role in improving clinical outcomes in a chemically-induced colitis model. The three strains were able to survive in the intestinal tract of C57BL/6J mice during the course of the intervention study. Furthermore, the disease activity index (DAI) of the animal …

Depression In Visual Impairment Trial (Depvit): A Randomized Clinical Trial Of Depression Treatments In People With Low Vision, Claire L. Nollett, Nathan Bray, Catey Bunce, Robin J. Casten, Rhiannon T. Edwards, Mark T. Hegel, Sarah Janikoun, Sandra E. Jumbe, Barbara Ryan, Julia Shearn

Dartmouth Scholarship

Purpose: The purpose of this study was to compare two interventions for depression, problem solving treatment (PST) and referral to the patient's physician, with a waiting-list control group in people with sight loss and depressive symptoms.

Methods: This was an assessor-masked, exploratory, multicenter, randomized clinical trial, with concurrent economic analysis. Of 1008 consecutive attendees at 14 low-vision rehabilitation centers in Britain, 43% (n = 430) screened positive for depressive symptoms on the Geriatric Depression Scale and 85 of these attendees participated in the trial. Eligible participants were randomized in the ratio 1:1:1 to PST, referral to their physician, or …

Galaxies Probing Galaxies At High Resolution: Co-Rotating Gas Associated With A Milky Way Analog At Z = 0.4, Aleksandar M. Diamond-Stanic, Alison L. Coil, John Moustakas, Christy A. Tremonti, Paul H. Sell, Alexander J. Mendez, Ryan C. Hickox, Greg H. Rudnick

Dartmouth Scholarship

We present results on gas flows in the halo of a Milky-Way-like galaxy at z = 0.413 based on high-resolution spectroscopy of a background galaxy. This is the first study of circumgalactic gas at high spectral resolution toward an extended background source (i.e., a galaxy rather than a quasar). Using long-slit spectroscopy of the foreground galaxy, we observe spatially extended Hα emission with a circular rotation velocity v circ ≈ 270 km s⁻¹. Using echelle spectroscopy of the background galaxy, we detect and absorption lines at an impact parameter ρ= 27 kpc that are blueshifted from systemic …

The Pseudomonas Aeruginosa Efflux Pump Mexghi-Opmd Transports A Natural Phenazine That Controls Gene Expression And Biofilm Development, Hassan Sakhtah, Leslie Koyama, Yihan Zhang, Diana K. Morales, Blanche Fields, Alexa Price-Whelan, Deborah Hogan

Dartmouth Scholarship

Redox-cycling compounds, including endogenously produced phenazine antibiotics, induce expression of the efflux pump MexGHI-OpmD in the opportunistic pathogen Pseudomonas aeruginosa Previous studies of P. aeruginosa virulence, physiology, and biofilm development have focused on the blue phenazine pyocyanin and the yellow phenazine-1-carboxylic acid (PCA). In P. aeruginosa phenazine biosynthesis, conversion of PCA to pyocyanin is presumed to proceed through the intermediate 5-methylphenazine-1-carboxylate (5-Me-PCA), a reactive compound that has eluded detection in most laboratory samples. Here, we apply electrochemical methods to directly detect 5-Me-PCA and find that it is transported by MexGHI-OpmD in P. aeruginosa strain PA14 planktonic and biofilm cells. We …