Anaerobic Microbial Transformation of Halogenated Aromatics and Fate Prediction Using Electron Density Modeling

Halogenated homo- and heterocyclic aromatics including disinfectants, pesticides and pharmaceuticals raise concern as persistent and toxic contaminants with often unknown fate. Remediation strategies and natural attenuation in anaerobic environments often build on microbial reductive dehalogenation. Here we describe the transformation of halogenated anilines, benzonitriles, phenols, methoxylated, or hydroxylated benzoic acids, pyridines, thiophenes, furoic acids, and benzenes by <i>Dehalococcoides mccartyi</i> strain CBDB1 and environmental fate modeling of the dehalogenation pathways. The compounds were chosen based on structural considerations to investigate the influence of functional groups present in a multitude of commercially used halogenated aromatics. Experimentally obtained growth yields were 0.1 to 5 × 10¹⁴ cells mol^–1 of halogen released (corresponding to 0.3–15.3 g protein mol^–1 halogen), and specific enzyme activities ranged from 4.5 to 87.4 nkat mg^–1 protein. Chlorinated electron-poor pyridines were not dechlorinated in contrast to electron-rich thiophenes. Three different partial charge models demonstrated that the regioselective removal of halogens is governed by the least negative partial charge of the halogen. Microbial reaction pathways combined with computational chemistry and pertinent literature findings on Co^I chemistry suggest that halide expulsion during reductive dehalogenation is initiated through single electron transfer from B₁₂Co^I to the apical halogen site

Replacing the Ethylmalonyl-CoA Pathway with the Glyoxylate Shunt Provides Metabolic Flexibility in the Central Carbon Metabolism of <i>Methylobacterium extorquens</i> AM1

The ethylmalonyl-CoA pathway (EMCP) is an anaplerotic reaction sequence in the central carbon metabolism of numerous Proteo- and Actinobacteria. The pathway features several CoA-bound mono- and dicarboxylic acids that are of interest as platform chemicals for the chemical industry. The EMCP, however, is essential for growth on C1 and C2 carbon substrates and therefore cannot be simply interrupted to drain these intermediates. In this study, we aimed at reengineering central carbon metabolism of the Alphaproteobacterium <i>Methylobacterium extorquens</i> AM1 for the specific production of EMCP derivatives in the supernatant. Establishing a heterologous glyoxylate shunt in <i>M. extorquens</i> AM1 restored wild type-like growth in several EMCP knockout strains on defined minimal medium with acetate as carbon source. We further engineered one of these strains that carried a deletion of the gene encoding crotonyl-CoA carboxylase/reductase to demonstrate in a proof-of-concept the specific production of crotonic acid in the supernatant on a defined minimal medium. Our experiments demonstrate that it is in principle possible to further exploit the EMCP by establishing an alternative central carbon metabolic pathway in <i>M. extorquens</i> AM1, opening many possibilities for the biotechnological production of EMCP-derived compounds in future

Participant flow from randomization in the ORBITAL intervention study to analyses of the present study.

<p>Abbreviations: BMI = body mass index, CABG = coronary artery bypass graft, HRQoL = health-related quality of life, ORBITAL = Open Label Primary Care Study Rosuvastatin Based Compliance Initiatives to Achievements of LDL Goals, PCI = percutaneous coronary intervention.</p

Bland Altman plot for baseline BMI calculated from the self-reported and physician-reported body weight.

<p>The bias (mean) between the two methods is marked by the full line (–), the upper and lower limits of agreement (mean ±2 standard deviations) by the dotted line (···) and the regression line by the broken line (− − −). Six observations are outside the axis range. Abbreviation: BMI = body mass index.</p

Baseline characteristics and SF-12 summary scores of the analyzed study population, stratified by BMI category.

<p>Abbreviations: LDL = low-density lipoprotein, SD = standard deviation, SF = Short Form.</p>1<p>Percentages may not add up due to rounding.</p>2<p>Score could range between 0 and 100 and was assessed with the SF-12 health status instrument.</p>3<p>Categorization by the number of school years needed for the different levels of school graduation.</p

Mean changes in the physical (part A) and mental (part B) SF-12 summary scores from baseline to 36-month follow-up according to baseline BMI category in three weight-change groups.

<p>Weight-change groups: weight loser (BMI change over 36 months <−0.5 kg/m²), stable weight (BMI change −0.5 to 0.5 kg/m²), and weight gainer (BMI change >0.5 kg/m²). Abbreviations: BMI = body mass index in kg/m², SF = Short Form.</p

Longitudinal association of change in BMI with the mental and physical SF-12 summary scores during the 3-year follow-up, stratified by sex and BMI category.

<p>Abbreviations: BMI = body mass index, CI = confidence intervals, SF = Short Form.</p>1<p>Stratified regression coefficients are reported only in the case of significant interaction terms in the basic model (P<0.05).</p>2<p>β can be interpreted as the change in SF-12 summary score per increase in BMI change of 1 kg/m² over time.</p>3<p>Basic model included the SF-12 summary score at all time points as the dependent variable and baseline BMI, change in BMI from baseline to all follow-up points, age, sex, study arm, interaction term time × study arm, and time-dependent smoking status as independent variables, n = 6726.</p>4<p>Further adjusted model consisting of the basic model additionally adjusted for education level, employment status, living situation, diagnosis of diabetes and hypertension, and history and time-dependent cumulative incidence of myocardial infarction/stroke and coronary artery bypass grafting/percutaneous coronary intervention within the previous 6 months, n = 6682.</p>5<p>Normal weight (BMI 18.5 to <25 kg/m²), overweight (BMI 25 to <30 kg/m²), and obese (BMI ≥30 kg/m²).</p

Cross-sectional association of baseline BMI with the mental and physical SF-12 summary scores, stratified by BMI category.

<p>Abbreviations: BMI = body mass index, CI = confidence intervals, SF = Short Form.</p>1<p>Stratified regression coefficients are reported only with significant interaction terms in the basic model (P<0.05).</p>2<p>β can be interpreted as difference in SF-12 summary score per increase in baseline BMI of 1 kg/m².</p>3<p>Basic model included the SF-12 summary score at baseline as the dependent variable and baseline BMI, age, sex, and smoking status at baseline as independent variables, n = 6726.</p>4<p>Further adjusted model consisting of the basic model additionally adjusted for education level, employment status, living situation, diagnosis of diabetes and hypertension, and history of myocardial infarction, stroke, coronary artery bypass grafting, and percutaneous coronary intervention at baseline, n = 6682.</p>5<p>Normal weight (BMI 18.5 to <25 kg/m²), overweight (BMI 25 to <30 kg/m²), and obese (BMI ≥30 kg/m²).</p