Metalloproteomics Reveals Multi-Level Stress Response in Escherichia coli When Exposed to Arsenite.

The arsRBC operon encodes a three-protein arsenic resistance system. ArsR regulates the transcription of the operon, while ArsB and ArsC are involved in exporting trivalent arsenic and reducing pentavalent arsenic, respectively. Previous research into Agrobacterium tumefaciens 5A has demonstrated that ArsR has regulatory control over a wide range of metal-related proteins and metabolic pathways. We hypothesized that ArsR has broad regulatory control in other Gram-negative bacteria and set out to test this. Here, we use differential proteomics to investigate changes caused by the presence of the arsR gene in human microbiome-relevant Escherichia coli during arsenite (AsIII) exposure. We show that ArsR has broad-ranging impacts such as the expression of TCA cycle enzymes during AsIII stress. Additionally, we found that the Isc [Fe-S] cluster and molybdenum cofactor assembly proteins are upregulated regardless of the presence of ArsR under these same conditions. An important finding from this differential proteomics analysis was the identification of response mechanisms that were strain-, ArsR-, and arsenic-specific, providing new clarity to this complex regulon. Given the widespread occurrence of the arsRBC operon, these findings should have broad applicability across microbial genera, including sensitive environments such as the human gastrointestinal tract.

Hot springs viruses at Yellowstone National Park have ancient origins and are adapted to thermophilic hosts.

Geothermal springs house unicellular red algae in the class Cyanidiophyceae that dominate the microbial biomass at these sites. Little is known about host-virus interactions in these environments. We analyzed the virus community associated with red algal mats in three neighboring habitats (creek, endolithic, soil) at Lemonade Creek, Yellowstone National Park (YNP), USA. We find that despite proximity, each habitat houses a unique collection of viruses, with the giant viruses, Megaviricetes, dominant in all three. The early branching phylogenetic position of genes encoded on metagenome assembled virus genomes (vMAGs) suggests that the YNP lineages are of ancient origin and not due to multiple invasions from mesophilic habitats. The existence of genomic footprints of adaptation to thermophily in the vMAGs is consistent with this idea. The Cyanidiophyceae at geothermal sites originated ca. 1.5 Bya and are therefore relevant to understanding biotic interactions on the early Earth.

Aerobic methane synthesis and dynamics in a river water environment.

Reports of aerobic biogenic methane (CH4) have generated new views about CH4 sources in nature. We examine this phenomenon in the free-flowing Yellowstone river wherein CH4 concentrations were tracked as a function of environmental conditions, phototrophic microorganisms (using chlorophyll a, Chl a, as proxy), as well as targeted methylated amines known to be associated with this process. CH4 was positively correlated with temperature and Chl a, although diurnal measurements showed CH4 concentrations were greatest during the night and lowest during maximal solar irradiation. CH4 efflux from the river surface was greater in quiescent edge waters (71-94 µmol m-2 d) than from open flowing current (~ 57 µmol m-2 d). Attempts to increase flux by disturbing the benthic environment in the quiescent water directly below (~ 1.0 m deep) or at varying distances (0-5 m) upstream of the flux chamber failed to increase surface flux. Glycine betaine (GB), dimethylamine and methylamine (MMA) were observed throughout the summer-long study, increasing during a period coinciding with a marked decline in Chl a, suggesting a lytic event led to their release; however, this did not correspond to increased CH4 concentrations. Spiking river water with GB or MMA yielded significantly greater CH4 than nonspiked controls, illustrating the metabolic potential of the river microbiome. In summary, this study provides evidence that: (1) phototrophic microorganisms are involved in CH4 synthesis in a river environment; (2) the river microbiome possesses the metabolic potential to convert methylated amines to CH4; and (3) river CH4 concentrations are dynamic diurnally as well as during the summer active months.

Revised classification of the Cyanidiophyceae based on plastid genome data with descriptions of the Cavernulicolales ord. nov. and Galdieriales ord. nov. (Rhodophyta).

The Cyanidiophyceae, an extremophilic red algal class, is distributed worldwide in extreme environments. Species grow either in acidic hot environments or in dim light conditions (e.g., "cave Cyanidium"). The taxonomy and classification systems are currently based on morphological, eco-physiological, and molecular phylogenetic characters; however, previous phylogenetic results showed hidden diversity of the Cyanidiophyceae and suggested a revision of the classification system. To clarify phylogenetic relationships within this red algal class, we employ a phylogenomic approach based on 15 plastomes (10 new) and 15 mitogenomes (seven new). Our phylogenies show consistent relationships among four lineages (Galdieria, "cave Cyanidium", Cyanidium, and Cyanidioschyzon lineages). Each lineage is distinguished by organellar genome characteristics. The "cave Cyanidium" lineage is a distinct clade that diverged after the Galdieria clade but within a larger monophyletic clade that included the Cyanidium and Cyanidioschyzon lineages. Because the "cave Cyanidium" lineage is a mesophilic lineage that differs substantially from the other three thermoacidophilic lineages, we describe it as a new order (Cavernulicolales). Based on this evidence, we reclassified the Cyanidiophyceae into four orders: Cyanidiales, Cyanidioschyzonales, Cavernulicolales ord. nov., and Galdieriales ord. nov. The genetic distance among these four orders is comparable to, or greater than, the distances found between other red algal orders and subclasses. Three new genera (Cavernulicola, Gronococcus, Sciadococcus), five new species (Galdieria javensis, Galdieria phlegrea, Galdieria yellowstonensis, Gronococcus sybilensis, Sciadococcus taiwanensis), and a new nomenclatural combination (Cavernulicola chilensis) are proposed.

A machine learning analysis of risk and protective factors of suicidal thoughts and behaviors in college students.

OBJECTIVE: To identify robust and reproducible factors associated with suicidal thoughts and behaviors (STBs) in college students. METHODS: 356 first-year university students completed a large battery of demographic and clinically-relevant self-report measures during the first semester of college and end-of-year (n = 228). Suicide Behaviors Questionnaire-Revised (SBQ-R) assessed STBs. A machine learning (ML) pipeline using stacking and nested cross-validation examined correlates of SBQ-R scores. RESULTS: 9.6% of students were identified at significant STBs risk by the SBQ-R. The ML algorithm explained 28.3% of variance (95%CI: 28-28.5%) in baseline SBQ-R scores, with depression severity, social isolation, meaning and purpose in life, and positive affect among the most important factors. There was a significant reduction in STBs at end-of-year with only 1.8% of students identified at significant risk. CONCLUSION: Analyses replicated known factors associated with STBs during the first semester of college and identified novel, potentially modifiable factors including positive affect and social connectedness.

Arsenic and Mercury Distribution in an Aquatic Food Chain: Importance of Femtoplankton and Picoplankton Filtration Fractions.

Arsenic (As) and mercury (Hg) were examined in the Yellowstone Lake food chain, focusing on two lake locations separated by approximately 20 km and differing in lake floor hydrothermal vent activity. Sampling spanned from femtoplankton to the main fish species, Yellowstone cutthroat trout and the apex predator lake trout. Mercury bioaccumulated in muscle and liver of both trout species, biomagnifying with age, whereas As decreased in older fish, which indicates differential exposure routes for these metal(loid)s. Mercury and As concentrations were higher in all food chain filter fractions (0.1-, 0.8-, and 3.0-µm filters) at the vent-associated Inflated Plain site, illustrating the impact of localized hydrothermal inputs. Femtoplankton and picoplankton size biomass (0.1- and 0.8-µm filters) accounted for 30%-70% of total Hg or As at both locations. By contrast, only approximately 4% of As and <1% of Hg were found in the 0.1-µm filtrate, indicating that comparatively little As or Hg actually exists as an ionic form or intercalated with humic compounds, a frequent assumption in freshwaters and marine waters. Ribosomal RNA (18S) gene sequencing of DNA derived from the 0.1-, 0.8-, and 3.0-µm filters showed significant eukaryote biomass in these fractions, providing a novel view of the femtoplankton and picoplankton size biomass, which assists in explaining why these fractions may contain such significant Hg and As. These results infer that femtoplankton and picoplankton metal(loid) loads represent aquatic food chain entry points that need to be accounted for and that are important for better understanding Hg and As biochemistry in aquatic systems. Environ Toxicol Chem 2023;42:225-241. © 2022 SETAC.

Neural processes of inhibitory control in American Indian peoples are associated with reduced mental health problems.

American Indians (AI) experience disproportionately high prevalence of suicide and substance use disorders (SUD). However, accounting for risk burden (e.g. historical trauma and discrimination), the likelihood of mental health disorders or SUD is similar or decreased compared with the broader population. Such findings have spurred psychological research examining the protective factors, but no studies have investigated its potential neural mechanisms. Inhibitory control is one of the potential neurobehavioral construct with demonstrated protective effects, but has not been examined in neuroimaging studies with AI populations specifically. We examined the incidence of suicidal thoughts and behaviors (STB) and SUD among AI (n = 76) and propensity matched (sex, age, income, IQ proxy and trauma exposure) non-Hispanic White (NHW) participants (n = 76). Among the AI sample, functional magnetic resonance imaging (fMRI) data recorded during the stop-signal task (SST) was examined in relation to STB and SUDs. AIs relative to NHW subjects displayed lower incidence of STB. AIs with no reported STBs showed greater activity in executive control regions during the SST compared with AI who endorsed STB. AI without SUD demonstrated lower activity relative to those individual reporting SUD. Results are consistent with a growing body of literature demonstrating the high level of risk burden driving disparate prevalence of mental health concerns in AI. Furthermore, differential activation during inhibitory control processing in AI individuals without STB may represent a neural mechanism of protective effects against mental health problems in AI. Future research is needed to elucidate sociocultural factors contributing protection against mental health outcomes in AIs and further delineate neural mechanisms with respect to specific concerns (e.g. SUD vs STB).

A randomized clinical trial of behavioral activation and exposure-based therapy for adults with generalized anxiety disorder.

Objective: Exposure-based therapy (EXP) and behavioral activation (BA) are empirically-supported behavioral intervention techniques that target avoidance and approach behavior to alleviate symptoms. Although EXP is an established treatment for generalized anxiety disorder (GAD), the effectiveness of BA for GAD has not been directly tested or compared with that of EXP. This study examined the efficacy of EXP and BA for adults with GAD. Method: In a randomized clinical trial (clinicaltrials.gov: NCT02807480) with partial blinding in Tulsa, OK, 102 adults with GAD were allocated to manualized, 10-session EXP or BA between April 2016-April 2021. Primary analyses were intention-to-treat and included the 94 (46 EXP, 48 BA) participants who started treatment. The GAD-7 self-report scale was the primary outcome measure. Results: Similar GAD-7 declines were observed at post-treatment for EXP (d=-0.97 [95% CI -1.40 to -0.53]) and BA (d=-1.14 [95% CI -1.57 to -0.70]), and were maintained through 6-month follow-up (EXP: d=-2.13, BA: d=-1.98). Compared to EXP, BA yielded more rapid declines in anxiety and depression scores during therapy (d=0.75-0.77), as well as lower anxiety and depression scores (d=0.13-0.14) and greater participant-rated improvement (d=0.64) at post-treatment. Bayesian analyses indicated 74-99% probability of greater change in BA than EXP at post-treatment. Conclusions: BA and EXP are both effective in treating GAD, and BA may confer greater benefit during treatment. Future research is warranted to inform personalized treatment approaches.

Striatal reactivity during emotion and reward relates to approach-avoidance conflict behaviour and is altered in adults with anxiety or depression.

BACKGROUND: We have previously reported activation in reward, salience and executive control regions during functional MRI (fMRI) using an approach-avoidance conflict (AAC) decision-making task with healthy adults. Further investigations into how anxiety and depressive disorders relate to differences in neural responses during AAC can inform their understanding and treatment. We tested the hypothesis that people with anxiety or depression have altered neural activation during AAC. METHODS: We compared 118 treatment-seeking adults with anxiety or depression and 58 healthy adults using linear mixed-effects models to examine group-level differences in neural activation (fMRI) during AAC decision-making. Correlational analyses examined relationships between behavioural and neural measures. RESULTS: Adults with anxiety or depression had greater striatal engagement when reacting to affective stimuli (p = 0.008, d = 0.31) regardless of valence, and weaker striatal engagement during reward feedback (p = 0.046, d = -0.27) regardless of the presence of monetary reward. They also had blunted amygdala activity during decision-making (p = 0.023, d = -0.32) regardless of the presence of conflict. Across groups, approach behaviour during conflict decision-making was inversely correlated with striatal activation during affective stimuli (p < 0.001, r = -0.28) and positively related to striatal activation during reward feedback (p < 0.001, r = 0.27). LIMITATIONS: Our transdiagnostic approach did not allow for comparisons between specific anxiety disorders, and our cross-sectional approach did not allow for causal inference. CONCLUSION: Anxiety and depression were associated with altered neural responses to AAC. Findings were consistent with the role of the striatum in action selection and reward responsivity, and they point toward striatal reactivity as a future treatment target. Blunting of amygdala activity in anxiety or depression may indicate a compensatory response to inhibit affective salience and maintain approach.

Active coping strategies and less pre-pandemic alcohol use relate to college student mental health during the COVID-19 pandemic.

Objective: To further delineate risk and resilience factors contributing to trajectories of mental health symptoms experienced by college students through the pandemic. Participants: n = 183 college students (67.2% female). Methods: Linear mixed models examined time effects on depression and anxiety. Propensity-matched subgroups exhibiting "increased" versus "low and stable" depression symptoms from before to after the pandemic-onset were compared on pre-pandemic demographic and psychological factors and COVID-related experiences and coping strategies. Results: Students experienced worsening of mental health symptoms throughout the pandemic, particularly during Fall 2020 compared with Fall 2019 (Depression scale d = -0.43 [95% CI: -0.65 to -0.21]). The propensity-matched subgroup exhibiting relative resilience ("low and stable" symptoms) reported less alcohol use prior to the pandemic, greater use of active coping strategies, and less of an impact on their college progress. Conclusions: Results point to several potential targets of screening and intervention to decrease residual impacts of the pandemic.

Limits to the generalizability of resting-state functional magnetic resonance imaging studies of youth: An examination of ABCD Study® baseline data.

This study examined how resting-state functional magnetic resonance imaging (rs-fMRI) data quality and availability relate to clinical and sociodemographic variables within the Adolescent Brain Cognitive Development Study. A sample of participants with an adequate sample of quality baseline rs-fMRI data containing low average motion (framewise displacement ≤ 0.15; low-noise; n = 4,356) was compared to a sample of participants without an adequate sample of quality data and/or containing high average motion (higher-noise; n = 7,437) using Chi-squared analyses and t-tests. A linear mixed model examined relationships between clinical and sociodemographic characteristics and average head motion in the sample with low-noise data. Relative to the sample with higher-noise data, the low-noise sample included more females, youth identified by parents as non-Hispanic white, and youth with married parents, higher parent education, and greater household incomes (ORs = 1.32-1.42). Youth in the low-noise sample were also older and had higher neurocognitive skills, lower BMIs, and fewer externalizing and neurodevelopmental problems (ds = 0.12-0.30). Within the low-noise sample, several clinical and demographic characteristics related to motion. Thus, participants with low-noise rs-fMRI data may be less representative of the general population and motion may remain a confound in this sample. Future rs-fMRI studies of youth should consider these limitations in the design and analysis stages in order to optimize the representativeness and clinical relevance of analyses and results.

Self-regulation of the posterior cingulate cortex with real-time fMRI neurofeedback augmented mindfulness training in healthy adolescents: A nonrandomized feasibility study.

Mindfulness training (MT) promotes the development of one's ability to observe and attend to internal and external experiences with objectivity and nonjudgment with evidence to improve psychological well-being. Real-time functional MRI neurofeedback (rtfMRI-nf) is a noninvasive method of modulating activity of a brain region or circuit. The posterior cingulate cortex (PCC) has been hypothesized to be an important hub instantiating a mindful state. This nonrandomized, single-arm study examined the feasibility and tolerability of training typically developing adolescents to self-regulate the posterior cingulate cortex (PCC) using rtfMRI-nf during MT. Thirty-four adolescents (mean age: 15 years; 14 females) completed the neurofeedback augmented mindfulness training task, including Focus-on-Breath (MT), Describe (self-referential thinking), and Rest conditions, across three neurofeedback and two non-neurofeedback runs (Observe, Transfer). Self-report assessments demonstrated the feasibility and tolerability of the task. Neurofeedback runs differed significantly from non-neurofeedback runs for the Focus-on-Breath versus Describe contrast, characterized by decreased activity in the PCC during the Focus-on-Breath condition (z = -2.38 to -6.27). MT neurofeedback neural representation further involved the medial prefrontal cortex, anterior cingulate cortex, dorsolateral prefrontal cortex, posterior insula, hippocampus, and amygdala. State awareness of physical sensations increased following rtfMRI-nf and was maintained at 1-week follow-up (Cohens' d = 0.69). Findings demonstrate feasibility and tolerability of rtfMRI-nf in healthy adolescents, replicates the role of PCC in MT, and demonstrate a potential neuromodulatory mechanism to leverage and streamline the learning of mindfulness practice. ( ClinicalTrials.gov identifier #NCT04053582; August 12, 2019).

Amplification of Positivity Therapy for Co-occurring Alcohol Use Disorder with Depression and Anxiety Symptoms: Pilot Feasibility Study and Case Series.

Positive valence system dysregulation is a relatively unexplored transdiagnostic mechanism and potential treatment target underpinning alcohol use and anxiety and depression symptoms. The current study examined the feasibility and potential benefit of a behavioral intervention focused on amplification of positivity (AMP) with eight adults (five female) diagnosed with alcohol use disorder and clinically significant depression or anxiety (ClinicalTrials.gov: NCT04278365). AMP for alcohol use (AMP-A) was delivered in 11 individual sessions involving positive activity interventions integrated alongside psychoeducation and alcohol use monitoring. Case descriptions are provided to illustrate treatment implementation. Treatment credibility and acceptability, participant endorsement of the therapy, and homework compliance were rated moderate to high. Exploratory, intent-to-treat analyses suggested medium to large effect sizes for post-treatment improvements in alcohol use, depression, anxiety, and positive affect. Results provide initial evidence of feasibility and acceptability of AMP-A and will be useful for informing future randomized clinical trials to examine clinical efficacy.

P300 amplitude during a monetary incentive delay task predicts future therapy completion in individuals with major depressive disorder.

INTRODUCTION: Treatment effectiveness for major depressive disorder (MDD) is often affected by client non-adherence, dropout, and non-response. Identification of client characteristics predicting successful treatment completion and/or response (i.e., symptom reduction) may be an important tool to increase intervention effectiveness. It is unclear whether neural attenuations in reward processing associated with MDD predict behavioral treatment outcome. METHODS: This study aimed to determine whether blunted neural responses to reward at baseline differentiate MDD (n = 60; 41 with comorbid anxiety) and healthy control (HC; n = 40) groups; and predict MDD completion of and response to 7-10 sessions of behavior therapy. Participants completed a monetary incentive delay (MID) task. The N200, P300, contingent negative variation (CNV) event related potentials (ERPs) and behavioral responses (reaction time [RT], correct hits) were quantified and extracted for cross-sectional group analyses. ERPs and behavioral responses demonstrating group differences were then used to predict therapy completion and response within MDD. RESULTS: MDD exhibited faster RT and smaller P300 amplitudes than HC across conditions. Within the MDD group, treatment completers (n = 37) exhibited larger P300 amplitudes than non-completers (n = 21). LIMITATIONS: This study comprises secondary analyses of EEG data; thus task parameters are not optimized to examine feedback ERPs from the paradigm. We did not examine heterogenous presentations of MDD; however, severity and comorbidity did not influence findings. CONCLUSIONS: Previous studies suggest that P300 is an index of motivational salience and stimulus resource allocation. In sum, individuals who deploy greater neural resources to task demands are more likely to persevere in behavioral therapy.

Long-term stability of computational parameters during approach-avoidance conflict in a transdiagnostic psychiatric patient sample.

Maladaptive behavior during approach-avoidance conflict (AAC) is common to multiple psychiatric disorders. Using computational modeling, we previously reported that individuals with depression, anxiety, and substance use disorders (DEP/ANX; SUDs) exhibited differences in decision uncertainty and sensitivity to negative outcomes versus reward (emotional conflict) relative to healthy controls (HCs). However, it remains unknown whether these computational parameters and group differences are stable over time. We analyzed 1-year follow-up data from a subset of the same participants (N = 325) to assess parameter stability and relationships to other clinical and task measures. We assessed group differences in the entire sample as well as a subset matched for age and IQ across HCs (N = 48), SUDs (N = 29), and DEP/ANX (N = 121). We also assessed 2-3 week reliability in a separate sample of 30 HCs. Emotional conflict and decision uncertainty parameters showed moderate 1-year intra-class correlations (.52 and .46, respectively) and moderate to excellent correlations over the shorter period (.84 and .54, respectively). Similar to previous baseline findings, parameters correlated with multiple response time measures (ps < .001) and self-reported anxiety (r = .30, p < .001) and decision difficulty (r = .44, p < .001). Linear mixed effects analyses revealed that patients remained higher in decision uncertainty (SUDs, p = .009) and lower in emotional conflict (SUDs, p = .004, DEP/ANX, p = .02) relative to HCs. This computational modelling approach may therefore offer relatively stable markers of transdiagnostic psychopathology.

Aerobic bacterial methane synthesis.

Reports of biogenic methane (CH4) synthesis associated with a range of organisms have steadily accumulated in the literature. This has not happened without controversy and in most cases the process is poorly understood at the gene and enzyme levels. In marine and freshwater environments, CH4 supersaturation of oxic surface waters has been termed the "methane paradox" because biological CH4 synthesis is viewed to be a strictly anaerobic process carried out by O2-sensitive methanogens. Interest in this phenomenon has surged within the past decade because of the importance of understanding sources and sinks of this potent greenhouse gas. In our work on Yellowstone Lake in Yellowstone National Park, we demonstrate microbiological conversion of methylamine to CH4 and isolate and characterize an Acidovorax sp. capable of this activity. Furthermore, we identify and clone a gene critical to this process (encodes pyridoxylamine phosphate-dependent aspartate aminotransferase) and demonstrate that this property can be transferred to Escherichia coli with this gene and will occur as a purified enzyme. This previously unrecognized process sheds light on environmental cycling of CH4, suggesting that O2-insensitive, ecologically relevant aerobic CH4 synthesis is likely of widespread distribution in the environment and should be considered in CH4 modeling efforts.

Introducing the ArsR-Regulated Arsenic Stimulon.

The microbial ars operon encodes the primary bacterial defense response to the environmental toxicant, arsenic. An important component of this operon is the arsR gene, which encodes ArsR, a member of the family of proteins categorized as DNA-binding transcriptional repressors. As currently documented, ArsR regulates its own expression as well as other genes in the same ars operon. This study examined the roles of four ArsR proteins in the well-developed model Gram-negative bacterium Agrobacterium tumefaciens 5A. RNASeq was used to compare and characterize gene expression profiles in ± arsenite-treated cells of the wild-type strain and in four different arsR mutants. We report that ArsR-controlled transcription regulation is truly global, extending well beyond the current ars operon model, and includes both repression as well as apparent activation effects. Many cellular functions are significantly influenced, including arsenic resistance, phosphate acquisition/metabolism, sugar transport, chemotaxis, copper tolerance, iron homeostasis, and many others. While there is evidence of some regulatory overlap, each ArsR exhibits its own regulatory profile. Furthermore, evidence of a regulatory hierarchy was observed; i.e. ArsR1 represses arsR4, ArsR4 activates arsR2, and ArsR2 represses arsR3. Additionally and unexpectedly, aioB (arsenite oxidase small subunit) expression was shown to be under partial positive control by ArsR2 and ArsR4. Summarizing, this study demonstrates the regulatory portfolio of arsenite-activated ArsR proteins and includes essentially all major cellular functions. The broad bandwidth of arsenic effects on microbial metabolism assists in explaining and understanding the full impact of arsenic in natural ecosystems, including the mammalian gut.

Test-retest reliability of approach-avoidance conflict decision-making during functional magnetic resonance imaging in healthy adults.

Neural and behavioral mechanisms during approach-avoidance conflict decision-making are relevant across various psychiatric disorders, particularly anxiety disorders. Studies using approach-avoidance conflict paradigms in healthy adults have identified preliminary neural mechanisms, but findings must be replicated and demonstrated as reliable before further application. This study sought to replicate previous findings and examine test-retest reliability of behavioral (approach behavior, reaction time) and neural (regions of interest [ROIs]) responses during an approach-avoidance conflict task conducted during functional magnetic resonance imaging (fMRI). Thirty healthy adults completed an approach-avoidance conflict task during fMRI on two occasions (mean interval: 17 days; range: 11-32). Effects of task condition during three task phases (decision-making, affective outcome and monetary reward) and intraclass correlation coefficients (ICCs) were calculated across time points. Results replicated that approach behavior was modulated by conflict during decision-making. ROI activations were replicated such that dorsal anterior cingulate cortex (dACC) was modulated by conflict during decision-making, and dACC, striatum, and anterior insula were modulated by valence during affective outcomes (p's <.0083). Approach behavior during conflict demonstrated excellent reliability (ICCs ≥.77). Activation of dACC during conflict decision-making and anterior insula during negative outcomes demonstrated fair reliability (ICCs = .51 and .54), and dACC and striatum activation demonstrated good reliability during negative outcomes (ICCs = .63 and .69). Two additional ROIs (amygdala, left dorsolateral prefrontal cortex) showed good reliability during negative outcomes (ICCs ≥.60). These results characterize several specific behavioral and neuroimaging responses that are replicable and sufficiently reliable during approach-avoidance conflict decision-making to support future utility.

A Single Microbiome Gene Alters Murine Susceptibility to Acute Arsenic Exposure.

Environmental toxicant exposure contributes to morbidity and mortality of many human diseases. With respect to arsenic, microbially driven chemical transformations dictate its toxicity and mobility in virtually every environment yet studied, so a general hypothesis is that the human gut microbiome determines disease outcome following exposure. However, the complex nature of the gut microbiome and the myriad of potential interactions with human cells/tissues make it challenging to quantify the influence of specific arsenic-active functions-a requisite step in developing effective disease prevention and/or clinical intervention strategies. To control both mammalian and microbial function during toxicant exposure, we genetically defined the gut microbiome of mice using only Escherichia coli strain, AW3110 (▵arsRBC), or the same strain carrying a single genome copy of the Fucus vesiculosus metallothionein gene (AW3110::fmt); a cysteine-rich peptide that complexes with arsenite, facilitating bioaccumulation and reducing its toxic effects. AW3110::fmt bioaccumulated significantly more arsenic and gnotobiotic mice colonized by this strain excreted significantly more arsenic in stool and accumulated significantly less arsenic in organs. Moreover, AW3110::fmt gnotobiotic mice were protected from acute toxicity exposure (20 ppm AsIII) relative to controls. This study demonstrates-in a highly controlled fashion-that a single microbiome function (arsenic bioaccumulation) encoded by a single gene in a single human gut microbiome bacterium significantly alters mammalian host arsenic exposure. The experimental model described herein allows for a highly controlled and directed assessment of microbiome functions, and is useful to quantify the influence of specific microbiome-arsenic interactions that help mitigate human disease.