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1.
BioData Min ; 17(1): 24, 2024 Jul 17.
Article in English | MEDLINE | ID: mdl-39020394

ABSTRACT

Pharmacokinetic (PK) studies can provide essential information on abuse liability of nicotine and tobacco products but are intrusive and must be conducted in a clinical environment. The objective of the study was to explore whether changes in plasma nicotine levels following use of an e-cigarette can be predicted from real time monitoring of physiological parameters and mouth level exposure (MLE) to nicotine before, during, and after e-cigarette vaping, using wearable devices. Such an approach would allow an -effective pre-screening process, reducing the number of clinical studies, reducing the number of products to be tested and the number of blood draws required in a clinical PK study Establishing such a prediction model might facilitate the longitudinal collection of data on product use and nicotine expression among consumers using nicotine products in their normal environments, thereby reducing the need for intrusive clinical studies while generating PK data related to product use in the real world.An exploratory machine learning model was developed to predict changes in plasma nicotine levels following the use of an e-cigarette; from real time monitoring of physiological parameters and MLE to nicotine before, during, and after e-cigarette vaping. This preliminary study identified key parameters, such as heart rate (HR), heart rate variability (HRV), and physiological stress (PS) that may act as predictors for an individual's plasma nicotine response (PK curve). Relative to baseline measurements (per participant), HR showed a significant increase for nicotine containing e-liquids and was consistent across sessions (intra-participant). Imputing missing values and training the model on all data resulted in 57% improvement from the original'learning' data and achieved a median validation R2 of 0.70.The study is in its exploratory phase, with limitations including a small and non-diverse sample size and reliance on data from a single e-cigarette product. These findings necessitate further research for validation and to enhance the model's generalisability and applicability in real-world settings. This study serves as a foundational step towards developing non-intrusive PK models for nicotine product use.

2.
J Appl Psychol ; 109(2): 169-201, 2024 Feb.
Article in English | MEDLINE | ID: mdl-37616110

ABSTRACT

Negative work behavior (NWB) occurs with concerning frequency in virtual work environments. Despite their prevalence and a substantial, multidisciplinary research literature on virtual negative behaviors in general, we lack clear answers regarding if, how, and why conditions differentiating virtual (i.e., computer-mediated) from face-to-face (F2F) work impact perpetrators', victims', and bystanders' involvement in NWB. These questions remain because of an assumed isomorphism (i.e., identical form) within the literature on NWB in F2F and virtual work. We explain why we cannot assume that what is known about perpetrator engagement, victim experience, and bystander intervention from studying F2F NWB applies uniformly to virtual negative work behavior (VNWB). Specifically, we identify how eight conditions of the virtual workplace facilitate three psychological enablers (i.e., ambiguity, anonymity, and (un)accountability) of perpetrators', victims', and bystanders' involvement in VNWB. In doing so, this integrative conceptual review advances a coherent understanding of what is (un)known about VNWB, integrates fragmented theoretical literature, and guides practical intervention. Importantly, we identify limitations of existing research practices that threaten the validity and generalizability of empirical findings. If not addressed, these issues will continue to undermine theoretical development and empirical investigations of F2F NWB and VNWB. Finally, this review points to new areas of inquiry that will meaningfully advance the understanding of NWB in the modern, increasingly virtual workplace. (PsycInfo Database Record (c) 2024 APA, all rights reserved).


Subject(s)
Crime Victims , Social Responsibility , Humans , Workplace/psychology , Crime Victims/psychology
3.
Health Commun ; 37(11): 1432-1441, 2022 10.
Article in English | MEDLINE | ID: mdl-33691559

ABSTRACT

The current study tested a theoretical account of how and when norms message features influence attitudes and intentions. Specifically, we examined whether functional matching and numeracy help to explain variation in persuasive outcomes following exposure to norms messaging. We executed two experiments to test our functional matching and numeracy assumptions in the context of alcohol consumption. Across both studies, our functional matching assumption was not supported. In Study 2, numeracy moderated the impact of descriptive norms message content on intentions to engage in heavy drinking, such that message exposure was associated with reduced drinking intentions among participants with greater levels of numeracy. In sum, the findings provided some evidence that the functional attitude approach lacked theoretical utility and that numeracy dictated the effect of norms message exposure on intentions.


Subject(s)
Attitude , Intention , Alcohol Drinking , Humans , Persuasive Communication
4.
AJR Am J Roentgenol ; 215(6): 1384-1388, 2020 12.
Article in English | MEDLINE | ID: mdl-33052740

ABSTRACT

OBJECTIVE. Radiology departments in tertiary care centers are frequently asked to perform secondary interpretations of imaging studies, particularly when a patient is transferred from a community hospital. Discrepancy rates in radiology vary widely, with low rates reported for preliminary resident reports that are overread by attending radiologists (2-6%) and higher rates (up to 56%) for secondary interpretations. Abdominal and pelvic imaging and cross-sectional imaging have the highest discrepancy rates. The purpose of our study was to determine the discrepancy rate and the most common reasons for discrepancies between abdominal and pelvic MRI reports obtained from outside institutions and secondary interpretations of these reports by a fellowship-trained radiologist at a tertiary care center. MATERIALS AND METHODS. We retrospectively identified 395 secondary MRI reports from January 2015 to December 2018 that were labeled as body MRI examinations at a tertiary care center. Thirty-eight cases were excluded for various reasons, including incorrect categorization or lack of outside report. We reviewed the outside reports, compared them with the secondary interpretations, and categorized the cases as discrepancy or no discrepancy. The discrepancies were subdivided into the most likely reason for the error using previously published categories; these categories were also divided into perceptive and cognitive errors. RESULTS. Of the 357 included cases, 246 (68.9%) had at least one discrepancy. The most common reason for error was faulty reasoning (34.3%), which is a cognitive error characterized by misidentifying an abnormality. Satisfaction of search, which is a perceptive error, was the most common reason for second discrepancies (15.0%). CONCLUSION. Secondary interpretations of body MR images at a tertiary care center identify a high rate of discrepancies, with cognitive error types predominating.


Subject(s)
Abdomen/diagnostic imaging , Clinical Competence , Diagnostic Errors/statistics & numerical data , Magnetic Resonance Imaging/standards , Adult , Aged , Aged, 80 and over , Contrast Media , Female , Humans , Male , Middle Aged , Observer Variation , Retrospective Studies
5.
J Racial Ethn Health Disparities ; 6(5): 962-972, 2019 10.
Article in English | MEDLINE | ID: mdl-31119610

ABSTRACT

BACKGROUND: Improvements in provider-patient relationships may help alleviate health disparities. Provider-patient race concordance and provider self-disclosure are variables that may help improve this relationship. PURPOSE: This study sought to answer if provider-patient race concordance and provider self-disclosure may improve patient trust, rapport, similarity, likeability, intention to disclose, satisfaction, behavioral intention to keep a provider, and intention to recommend a provider, while using empathy as a covariate. METHODS: Using 882 White or Black participants, the current research used a 2 × 2 online experimental design. Participants were asked to read a vignette in which they were told they had borderline high cholesterol and needed to eat a healthier diet, by either a Black or White male physician, who either self-disclosed or did not self-disclose regarding their own struggle to eat a healthy diet. After reading this vignette, participants were surveyed regarding the dependent variables of interest. RESULTS: Participants in a Black concordant dyad reported higher levels of similarity than those in any other dyad. Provider self-disclosure led to higher levels of trust, rapport, similarity, likeability, intention to disclose, satisfaction, behavioral intention to continue using the provider, and intention to recommend the provider. No interaction effects were found. CONCLUSION: While it is possible, based on past research, that race-concordant pairings may lead to trust via similarity, provider self-disclosure directly increased perceptions of trust as well as providing numerous other benefits. This study supports the importance of trainings for providers on health-related self-disclosure to benefit both parties in provider-patient dyads.


Subject(s)
Attitude to Health/ethnology , Disclosure/statistics & numerical data , Physician-Patient Relations , Physicians/psychology , Physicians/statistics & numerical data , Racial Groups/statistics & numerical data , Adolescent , Adult , Black or African American/psychology , Black or African American/statistics & numerical data , Aged , Aged, 80 and over , Female , Health Status Disparities , Humans , Intention , Male , Middle Aged , Trust/psychology , White People/psychology , White People/statistics & numerical data , Young Adult
6.
J Ultrasound Med ; 38(4): 1069-1073, 2019 Apr.
Article in English | MEDLINE | ID: mdl-30196569

ABSTRACT

Commercially produced ultrasound coupling gel is often a scarce resource in rural regions of low-income countries that use sonography as their main imaging modality and, when available, may be cost prohibitive. Various homemade gels were created and tested to assure image quality was not compromised. Glucomannan-based gel and guar gum-based gel had superior physical properties in initial testing and showed no substantial difference compared with commercially available ultrasound gel on subject and phantom imaging and analysis (P > .05 using a 1-tailed sign test). Neither gel required heating, attracted insects, damaged ultrasound transducers, stained samples of clothing, or had harmful effects to subjects.


Subject(s)
Gels/standards , Image Interpretation, Computer-Assisted/instrumentation , Ultrasonography/methods , Costs and Cost Analysis , Developing Countries , Galactans/chemistry , Galactans/economics , Gels/chemistry , Gels/economics , Humans , Image Interpretation, Computer-Assisted/standards , Mannans/chemistry , Mannans/economics , Phantoms, Imaging , Plant Gums/chemistry , Plant Gums/economics , Poverty , Ultrasonography/economics , Ultrasonography/standards , Viscosity
7.
J Health Commun ; 23(10-11): 956-966, 2018.
Article in English | MEDLINE | ID: mdl-30488787

ABSTRACT

This study examines message exposure and belief structures in the context of tobacco prevention and education efforts. Though it is imperative that researchers identify and test messaging strategies that move beliefs in the desired direction, these efforts must take care to consider the existing belief structures of the target audience. A pretest-posttest design was employed in order to extend an existing tobacco-free initiative. The study examined how participants structured their beliefs about tobacco and the initiative at the first time point (T1: N = 404) and tested the impact of persuasive messages at a second time point (T2: N = 192). The findings indicated that while one message produced change in a targeted norms-oriented belief, a constellation of messages hold promise for modifying a broader belief structure. The results are discussed in terms of their implications for message design and tobacco-free initiatives.


Subject(s)
Electronic Nicotine Delivery Systems , Health Communication , Health Knowledge, Attitudes, Practice , Adolescent , Adult , Female , Humans , Male , Middle Aged , Smoking Cessation/methods , Surveys and Questionnaires , Young Adult
9.
J Empir Res Hum Res Ethics ; 13(1): 50-60, 2018 02.
Article in English | MEDLINE | ID: mdl-29117849

ABSTRACT

Participants often do not read consent forms in social science research. This is not surprising, especially for online studies, given they do not typically offer greater risk than what is encountered in daily life. However, if no one is reading, are participants really informed? This study used previous research to craft experimentally manipulated consent forms utilizing different visual presentations (e.g., greater use of line spacing, bullets, bolding, diagrams). Participants ( n = 547) were randomly exposed to one of seven form variations. Results found no significant differences between forms in reading or comprehension. Open-ended questions asked participants why they do not read consent forms and what would influence them to read the forms. Participants most frequently stated forms need to be shorter, and important information needs to be highlighted. We suggest improvements to informed consent forms, including removing much of the information that is constant across forms, and only including unique aspects of studies.


Subject(s)
Attitude , Choice Behavior , Consent Forms , Internet , Reading , Research , Social Sciences , Adolescent , Adult , Comprehension , Female , Humans , Informed Consent , Male , Motivation , Surveys and Questionnaires , Young Adult
10.
J Soc Psychol ; 157(1): 47-63, 2017.
Article in English | MEDLINE | ID: mdl-26886500

ABSTRACT

Several competing models have been put forth regarding the role of identity in the reasoned action framework. The standard model proposes that identity is a background variable. Under a typical augmented model, identity is treated as an additional direct predictor of intention and behavior. Alternatively, it has been proposed that identity measures are inadvertent indicators of an underlying intention factor (e.g., a manifest-intention model). In order to test these competing hypotheses, we used data from 73 independent studies (total N = 23,917) to conduct a series of meta-analytic structural equation models. We also tested for moderation effects based on whether there was a match between identity constructs and the target behaviors examined (e.g., if the study examined a "smoker identity" and "smoking behavior," there would be a match; if the study examined a "health conscious identity" and "smoking behavior," there would not be a match). Average effects among primary reasoned action variables were all substantial, rs = .37-.69. Results gave evidence for the manifest-intention model over the other explanations, and a moderation effect by identity-behavior matching.


Subject(s)
Behavior , Group Processes , Social Identification , Humans
11.
Health Commun ; 32(3): 279-287, 2017 03.
Article in English | MEDLINE | ID: mdl-27219106

ABSTRACT

Evidence regarding possible environmental causes of breast cancer is advancing. Often, however, the public is not informed about these advances in a manner that is easily understandable. This research translates findings from biologists into messages at two literacy levels about perfluorooctanoic acid (PFOA), a possible environmental contributor to breast cancer. The Heuristic Systematic Model (HSM) was used to investigate how ability, motivation, and systematic and heuristic processing lead to risk beliefs and, ultimately, to negative attitudes for individuals receiving translated scientific messages about PFOA. Participants (N = 1,389) came from the Dr. Susan Love Research Foundation's Army of Women. Findings indicated that ability, in the form of translated messages, predicted systematic processing, operationalized as knowledge gain, which was negatively associated with formation of risk beliefs that led to negative attitudes toward PFOA. Heuristic processing cues, operationalized as perceived message quality and source credibility, were positively associated with risk beliefs, which predicted negative attitudes about PFOA. Overall, more knowledge and lower literacy messages led to lower perceived risk, while greater involvement and ratings of heuristic cues led to greater risk perceptions. This is an example of a research, translation, and dissemination team effort in which biologists created knowledge, communication scholars translated and tested messages, and advocates were participants and those who disseminated messages.


Subject(s)
Breast Neoplasms/chemically induced , Caprylates/adverse effects , Environmental Health , Fluorocarbons/adverse effects , Health Communication , Health Knowledge, Attitudes, Practice , Female , Heuristics , Humans , Middle Aged , Motivation , Risk Factors
12.
J Cancer Educ ; 31(2): 389-96, 2016 Jun.
Article in English | MEDLINE | ID: mdl-25903053

ABSTRACT

Results of ongoing scientific research on environmental determinants of breast cancer are not typically presented to the public in ways they can easily understand and use to take preventive actions. In this study, results of scientific studies on progesterone exposure as a risk factor for breast cancer were translated into high and low literacy level messages. Using the heuristic systematic model, this study examined how ability, motivation, and message processing (heuristic and systematic) influenced perceptions of risk beliefs and negative attitudes about progesterone exposure among women who read the translated scientific messages. Among the 1254 participants, those given the higher literacy level message had greater perceptions of risk about progesterone. Heuristic message cues of source credibility and perceived message quality, as well as motivation, also predicted risk beliefs. Finally, risk beliefs were a strong predictor of negative attitudes about exposure to progesterone. The results can help improve health education message design in terms of practitioners having better knowledge of message features that are the most persuasive to the target audiences on this topic.


Subject(s)
Breast Neoplasms/chemically induced , Health Communication , Health Knowledge, Attitudes, Practice , Health Literacy , Heuristics , Models, Psychological , Progesterone/adverse effects , Adult , Aged , Environmental Health , Female , Follow-Up Studies , Humans , Middle Aged , Motivation , Persuasive Communication , Progestins/adverse effects , Risk Factors , Young Adult
13.
J Health Commun ; 20(12): 1449-57, 2015.
Article in English | MEDLINE | ID: mdl-26332404

ABSTRACT

The reported study explored the implications of informal computer-mediated social support for the well-being of individuals coping with illness over the course of 3 years. A panel study was conducted in which respondents--bloggers writing about their experiences living with a health condition--reported on their perceptions of social support and well-being during 2010 and again during 2013. Among respondents who completed both questionnaires (n = 49), increases in support availability from family and friends were related to improvements in bloggers' health self-efficacy as well as improvements in bloggers' loneliness, particularly among those who also experienced increased support availability from blog readers. Increased blog reader support availability was associated with improvements in bloggers' health-related uncertainty. Among respondents who completed the initial questionnaire (N = 121), a survival analysis showed that neither support available from family and friends nor support from blog readers predicted continued health blogging over the 3-year period.


Subject(s)
Adaptation, Psychological , Attitude to Health , Blogging , Social Support , Adult , Aged , Family/psychology , Female , Friends/psychology , Humans , Loneliness/psychology , Longitudinal Studies , Male , Middle Aged , Self Efficacy , Surveys and Questionnaires , Young Adult
14.
Sci Rep ; 5: 11823, 2015 Jul 03.
Article in English | MEDLINE | ID: mdl-26139349

ABSTRACT

Spin-polarized electrons can move a ferromagnetic domain wall through the transfer of spin angular momentum when current flows in a magnetic nanowire. Such current induced control of a domain wall is of significant interest due to its potential application for low power ultra high-density data storage. In previous reports, it has been observed that the motion of the domain wall always happens parallel to the current flow - either in the same or opposite direction depending on the specific nature of the interaction. In contrast, here we demonstrate deterministic control of a ferromagnetic domain wall orthogonal to current flow by exploiting the spin orbit torque in a perpendicularly polarized Ta/CoFeB/MgO heterostructure in presence of an in-plane magnetic field. Reversing the polarity of either the current flow or the in-plane field is found to reverse the direction of the domain wall motion. Notably, such orthogonal motion with respect to current flow is not possible from traditional spin transfer torque driven domain wall propagation even in presence of an external magnetic field. Therefore the domain wall motion happens purely due to spin orbit torque. These results represent a completely new degree of freedom in current induced control of a ferromagnetic domain wall.

15.
Mol Microbiol ; 2014 Oct 08.
Article in English | MEDLINE | ID: mdl-25294408

ABSTRACT

Microbial depolymerization of plant cell walls contributes to global carbon balance and is a critical component of renewable energy. The genomes of lignocellulose degrading microorganisms encode diverse classes of carbohydrate modifying enzymes, although currently there is a paucity of knowledge on the role of these proteins in vivo. We report the comprehensive analysis of the cellulose degradation system in the saprophytic bacterium Cellvibrio japonicus. Gene expression profiling of C. japonicus demonstrated that three of the 12 predicted ß-1,4 endoglucanases (cel5A, cel5B, and cel45A) and the sole predicted cellobiohydrolase (cel6A) showed elevated expression during growth on cellulose. Targeted gene disruptions of all 13 predicted cellulase genes showed that only cel5B and cel6A were required for optimal growth on cellulose. Our analysis also identified three additional genes required for cellulose degradation: lpmo10B encodes a lytic polysaccharide monooxygenase (LPMO), while cbp2D and cbp2E encode proteins containing carbohydrate binding modules and predicted cytochrome domains for electron transfer. CjLPMO10B oxidized cellulose and Cbp2D demonstrated spectral properties consistent with redox function. Collectively, this report provides insight into the biological role of LPMOs and redox proteins in cellulose utilization and suggests that C. japonicus utilizes a combination of hydrolytic and oxidative cleavage mechanisms to degrade cellulose.

16.
PLoS One ; 9(9): e107499, 2014.
Article in English | MEDLINE | ID: mdl-25222864

ABSTRACT

The inability of the yeast Saccharomyces cerevisiae to ferment xylose effectively under anaerobic conditions is a major barrier to economical production of lignocellulosic biofuels. Although genetic approaches have enabled engineering of S. cerevisiae to convert xylose efficiently into ethanol in defined lab medium, few strains are able to ferment xylose from lignocellulosic hydrolysates in the absence of oxygen. This limited xylose conversion is believed to result from small molecules generated during biomass pretreatment and hydrolysis, which induce cellular stress and impair metabolism. Here, we describe the development of a xylose-fermenting S. cerevisiae strain with tolerance to a range of pretreated and hydrolyzed lignocellulose, including Ammonia Fiber Expansion (AFEX)-pretreated corn stover hydrolysate (ACSH). We genetically engineered a hydrolysate-resistant yeast strain with bacterial xylose isomerase and then applied two separate stages of aerobic and anaerobic directed evolution. The emergent S. cerevisiae strain rapidly converted xylose from lab medium and ACSH to ethanol under strict anaerobic conditions. Metabolomic, genetic and biochemical analyses suggested that a missense mutation in GRE3, which was acquired during the anaerobic evolution, contributed toward improved xylose conversion by reducing intracellular production of xylitol, an inhibitor of xylose isomerase. These results validate our combinatorial approach, which utilized phenotypic strain selection, rational engineering and directed evolution for the generation of a robust S. cerevisiae strain with the ability to ferment xylose anaerobically from ACSH.


Subject(s)
Biofuels , Lignin/metabolism , Saccharomyces cerevisiae/genetics , Xylose/metabolism , Ammonia/metabolism , Anaerobiosis , Biomass , Ethanol/metabolism , Fermentation , Genetic Engineering , Hydrolysis , Saccharomyces cerevisiae/enzymology , Xylose/genetics , Zea mays/metabolism
17.
Front Microbiol ; 5: 402, 2014.
Article in English | MEDLINE | ID: mdl-25177315

ABSTRACT

Efficient microbial conversion of lignocellulosic hydrolysates to biofuels is a key barrier to the economically viable deployment of lignocellulosic biofuels. A chief contributor to this barrier is the impact on microbial processes and energy metabolism of lignocellulose-derived inhibitors, including phenolic carboxylates, phenolic amides (for ammonia-pretreated biomass), phenolic aldehydes, and furfurals. To understand the bacterial pathways induced by inhibitors present in ammonia-pretreated biomass hydrolysates, which are less well studied than acid-pretreated biomass hydrolysates, we developed and exploited synthetic mimics of ammonia-pretreated corn stover hydrolysate (ACSH). To determine regulatory responses to the inhibitors normally present in ACSH, we measured transcript and protein levels in an Escherichia coli ethanologen using RNA-seq and quantitative proteomics during fermentation to ethanol of synthetic hydrolysates containing or lacking the inhibitors. Our study identified four major regulators mediating these responses, the MarA/SoxS/Rob network, AaeR, FrmR, and YqhC. Induction of these regulons was correlated with a reduced rate of ethanol production, buildup of pyruvate, depletion of ATP and NAD(P)H, and an inhibition of xylose conversion. The aromatic aldehyde inhibitor 5-hydroxymethylfurfural appeared to be reduced to its alcohol form by the ethanologen during fermentation, whereas phenolic acid and amide inhibitors were not metabolized. Together, our findings establish that the major regulatory responses to lignocellulose-derived inhibitors are mediated by transcriptional rather than translational regulators, suggest that energy consumed for inhibitor efflux and detoxification may limit biofuel production, and identify a network of regulators for future synthetic biology efforts.

18.
Doc Ophthalmol ; 129(2): 115-22, 2014 Oct.
Article in English | MEDLINE | ID: mdl-24985710

ABSTRACT

PURPOSE: To compare the modified signal-to-noise ratio (SNR*) of multifocal visual evoked potential (mfVEP) responses elicited by a cathode ray tube (CRT) and liquid crystal display (LCD) monitor in normal subjects. METHODS: An LCD monitor and CRT monitor were luminance and contrast matched. Luminance stability and the effect of viewing angle on luminance and contrast was measured for both screens. The SNR* of mfVEP responses from 15 normal subjects was compared between the stimulators using repeated measures analysis of variance. RESULTS: The CRT monitor took 10 min from switch on to reach the desired luminance compared to 60 min for the LCD monitor. LCD luminance was sensitive to variations in ambient temperature, fluctuating by 10 cd/m(-2) over approximately 20-27 °C, whereas CRT luminance was stable. Luminance variation from the centre to the edge of the CRT screen was 8 % when viewed perpendicularly and 28 % when viewed at an angle of 25°, compared to 24 and 46 %, respectively, for the LCD screen. Contrast was >94 % and varied by <3 % across both monitors for both viewing conditions. There was no significant difference in SNR* between responses elicited by the two stimulators (p = 0.76). CONCLUSIONS: CRT and LCD stimulators elicited mfVEP responses with similar SNR* in normal subjects. This study highlighted practical issues with the use of LCD monitors as visual stimulators, particularly with regard to warm-up time, luminance stability and luminance uniformity.


Subject(s)
Cathode Ray Tube , Data Display , Evoked Potentials, Visual/physiology , Liquid Crystals , Photic Stimulation/instrumentation , Adult , Calibration , Female , Healthy Volunteers , Humans , Light , Male , Middle Aged , Signal-To-Noise Ratio , Young Adult
19.
Proc Natl Acad Sci U S A ; 111(25): E2576-85, 2014 Jun 24.
Article in English | MEDLINE | ID: mdl-24927582

ABSTRACT

The molecular mechanisms of ethanol toxicity and tolerance in bacteria, although important for biotechnology and bioenergy applications, remain incompletely understood. Genetic studies have identified potential cellular targets for ethanol and have revealed multiple mechanisms of tolerance, but it remains difficult to separate the direct and indirect effects of ethanol. We used adaptive evolution to generate spontaneous ethanol-tolerant strains of Escherichia coli, and then characterized mechanisms of toxicity and resistance using genome-scale DNAseq, RNAseq, and ribosome profiling coupled with specific assays of ribosome and RNA polymerase function. Evolved alleles of metJ, rho, and rpsQ recapitulated most of the observed ethanol tolerance, implicating translation and transcription as key processes affected by ethanol. Ethanol induced miscoding errors during protein synthesis, from which the evolved rpsQ allele protected cells by increasing ribosome accuracy. Ribosome profiling and RNAseq analyses established that ethanol negatively affects transcriptional and translational processivity. Ethanol-stressed cells exhibited ribosomal stalling at internal AUG codons, which may be ameliorated by the adaptive inactivation of the MetJ repressor of methionine biosynthesis genes. Ethanol also caused aberrant intragenic transcription termination for mRNAs with low ribosome density, which was reduced in a strain with the adaptive rho mutation. Furthermore, ethanol inhibited transcript elongation by RNA polymerase in vitro. We propose that ethanol-induced inhibition and uncoupling of mRNA and protein synthesis through direct effects on ribosomes and RNA polymerase conformations are major contributors to ethanol toxicity in E. coli, and that adaptive mutations in metJ, rho, and rpsQ help protect these central dogma processes in the presence of ethanol.


Subject(s)
Drug Resistance, Bacterial , Escherichia coli K12 , Escherichia coli Proteins , Ethanol/pharmacology , Protein Biosynthesis , Solvents/pharmacology , Transcription, Genetic , Alleles , Drug Resistance, Bacterial/drug effects , Drug Resistance, Bacterial/genetics , Escherichia coli K12/genetics , Escherichia coli K12/metabolism , Escherichia coli Proteins/genetics , Escherichia coli Proteins/metabolism , Genome-Wide Association Study , Protein Biosynthesis/drug effects , Protein Biosynthesis/genetics , Transcription, Genetic/drug effects , Transcription, Genetic/genetics
20.
Front Microbiol ; 5: 90, 2014.
Article in English | MEDLINE | ID: mdl-24672514

ABSTRACT

Lignocellulosic hydrolysate (LCH) inhibitors are a large class of bioactive molecules that arise from pretreatment, hydrolysis, and fermentation of plant biomass. These diverse compounds reduce lignocellulosic biofuel yields by inhibiting cellular processes and diverting energy into cellular responses. LCH inhibitors present one of the most significant challenges to efficient biofuel production by microbes. Development of new strains that lessen the effects of LCH inhibitors is an economically favorable strategy relative to expensive detoxification methods that also can reduce sugar content in deconstructed biomass. Systems biology analyses and metabolic modeling combined with directed evolution and synthetic biology are successful strategies for biocatalyst development, and methods that leverage state-of-the-art tools are needed to overcome inhibitors more completely. This perspective considers the energetic costs of LCH inhibitors and technologies that can be used to overcome their drain on conversion efficiency. We suggest academic and commercial research groups could benefit by sharing data on LCH inhibitors and implementing "translational biofuel research."

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