Enhanced upgrading of lignocellulosic substrates by coculture of Saccharomyces cerevisiae and Acinetobacter baylyi ADP1

BACKGROUND

Lignocellulosic biomass as feedstock has a huge potential for biochemical production. Still, efficient utilization of hydrolysates derived from lignocellulose is challenged by their complex and heterogeneous composition and the presence of inhibitory compounds, such as furan aldehydes. Using microbial consortia where two specialized microbes complement each other could serve as a potential approach to improve the efficiency of lignocellulosic biomass upgrading.

RESULTS

This study describes the simultaneous inhibitor detoxification and production of lactic acid and wax esters from a synthetic lignocellulosic hydrolysate by a defined coculture of engineered Saccharomyces cerevisiae and Acinetobacter baylyi ADP1. A. baylyi ADP1 showed efficient bioconversion of furan aldehydes present in the hydrolysate, namely furfural and 5-hydroxymethylfurfural, and did not compete for substrates with S. cerevisiae, highlighting its potential as a coculture partner. Furthermore, the remaining carbon sources and byproducts of S. cerevisiae were directed to wax ester production by A. baylyi ADP1. The lactic acid productivity of S. cerevisiae was improved approximately 1.5-fold (to 0.41 ± 0.08 g/L/h) in the coculture with A. baylyi ADP1, compared to a monoculture of S. cerevisiae.

CONCLUSION

The coculture of yeast and bacterium was shown to improve the consumption of lignocellulosic substrates and the productivity of lactic acid from a synthetic lignocellulosic hydrolysate. The high detoxification capacity and the ability to produce high-value products by A. baylyi ADP1 demonstrates the strain to be a potential candidate for coculture to increase production efficiency and economics of S. cerevisiae fermentations.

Incidence and predictors of thermal oesophageal and vagus nerve injuries in Ablation Index-guided high-power-short-duration ablation of atrial fibrillation: a prospective study

AIMS

High-power-short-duration (HPSD) ablation is an effective treatment for atrial fibrillation but poses risks of thermal injuries to the oesophagus and vagus nerve. This study aims to investigate incidence and predictors of thermal injuries, employing machine learning.

METHODS AND RESULTS

A prospective observational study was conducted at Leipzig Heart Centre, Germany, excluding patients with multiple prior ablations. All patients received Ablation Index-guided HPSD ablation and subsequent oesophagogastroduodenoscopy. A machine learning algorithm categorized ablation points by atrial location and analysed ablation data, including Ablation Index, focusing on the posterior wall. The study is registered in clinicaltrials.gov (NCT05709756). Between February 2021 and August 2023, 238 patients were enrolled, of whom 18 (7.6%; nine oesophagus, eight vagus nerve, one both) developed thermal injuries, including eight oesophageal erythemata, two ulcers, and no fistula. Higher mean force (15.8 ± 3.9 g vs. 13.6 ± 3.9 g, P = 0.022), ablation point quantity (61.50 ± 20.45 vs. 48.16 ± 19.60, P = 0.007), and total and maximum Ablation Index (24 114 ± 8765 vs. 18 894 ± 7863, P = 0.008; 499 ± 95 vs. 473 ± 44, P = 0.04, respectively) at the posterior wall, but not oesophagus location, correlated significantly with thermal injury occurrence. Patients with thermal injuries had significantly lower distances between left atrium and oesophagus (3.0 ± 1.5 mm vs. 4.4 ± 2.1 mm, P = 0.012) and smaller atrial surface areas (24.9 ± 6.5 cm2 vs. 29.5 ± 7.5 cm2, P = 0.032).

CONCLUSION

The low thermal lesion's rate (7.6%) during Ablation Index-guided HPSD ablation for atrial fibrillation is noteworthy. Machine learning based ablation data analysis identified several potential predictors of thermal injuries. The correlation between machine learning output and injury development suggests the potential for a clinical tool to enhance procedural safety.

Engineering cell morphology by CRISPR interference in Acinetobacter baylyi ADP1

Microbial production of intracellular compounds can be engineered by redirecting the carbon flux towards products and increasing the cell size. Potential engineering strategies include exploiting clustered regularly interspaced short palindromic repeats interference (CRISPRi)-based tools for controlling gene expression. Here, we applied CRISPRi for engineering Acinetobacter baylyi ADP1, a model bacterium for synthesizing intracellular storage lipids, namely wax esters. We first established an inducible CRISPRi system for strain ADP1, which enables tightly controlled repression of target genes. We then targeted the glyoxylate shunt to redirect carbon flow towards wax esters. Second, we successfully employed CRISPRi for modifying cell morphology by repressing ftsZ, an essential gene required for cell division, in combination with targeted knock-outs to generate significantly enlarged filamentous or spherical cells respectively. The engineered cells sustained increased wax ester production metrics, demonstrating the potential of cell morphology engineering in the production of intracellular lipids.

Role of assist device implantation and heart transplantation in the long-term outcome of patients with structural heart disease after catheter ablation of ventricular tachycardia

Introduction

Ablation of ventricular tachycardias (VTs) in patients with structural heart disease (SHD) has been associated with advanced heart failure and poor survival.

Methods and results

This matched case-control study sought to assess the difference in survival after left ventricular assist device (LVAD) implantation and/or heart transplantation (HTX) in SHD patients undergoing VT ablation. From the initial cohort of 309 SHD patients undergoing VT ablation (187 ischemic cardiomyopathy, mean age 64 ± 12 years, ejection fraction of 34 ± 13%), 15 patients received an LVAD and nine patients HTX after VT ablation during a follow-up period of 44 ± 33 months.

Long-term survival after LVAD did not differ from the matched control group (p = 0.761), although the cause of lethal events was different. All post-HTX patients survived during follow-up.

Conclusion

In this matched case-control study on patients with SHD undergoing VT ablation, patients that received LVAD implantation had similar survival compared to the control group after 4‑year follow-up, while the patients with HTX had a significantly better outcome.

Wax ester production in nitrogen-rich conditions by metabolically engineered Acinetobacter baylyi ADP1

Metabolic engineering can be used as a powerful tool to redirect cell resources towards product synthesis, also in conditions that are not optimal for the production. An example of synthesis strongly dependent on external conditions is the production of storage lipids, which typically requires a high carbon/nitrogen ratio. This requirement also limits the use of abundant nitrogen-rich materials, such as industrial protein by-products, as substrates for lipid production. Acinetobacter baylyi ADP1 is known for its ability to produce industrially interesting storage lipids, namely wax esters (WEs). Here, we engineered A. baylyi ADP1 by deleting the gene aceA encoding for isocitrate lyase and overexpressing fatty acyl-CoA reductase Acr1 in the wax ester production pathway to allow redirection of carbon towards WEs. This strategy led to 3-fold improvement in yield (0.075 ​g/g glucose) and 3.15-fold improvement in titer (1.82 ​g/L) and productivity (0.038 ​g/L/h) by a simple one-stage batch cultivation with glucose as carbon source. The engineered strain accumulated up to 27% WEs of cell dry weight. The titer and cellular WE content are the highest reported to date among microbes. We further showed that the engineering strategy alleviated the inherent requirement for high carbon/nitrogen ratio and demonstrated the production of wax esters using nitrogen-rich substrates including casamino acids, yeast extract, and baker's yeast hydrolysate, which support biomass production but not WE production in wild-type cells. The study demonstrates the power of metabolic engineering in overcoming natural limitations in the production of storage lipids.

Abstract SY21-03: Shutting off cancer's fountain of youth: Targeting metabolism to block repair and reverse immortality

The altered metabolism of cancer cells, first recognized by Warburg as aerobic glycolysis, has often been ascribed to answering increased needs for macromolecular biosynthesis to support rapid tumor growth. Recent discoveries that mutations leading to accumulation of fumarate, succinate or 2-hydroxyglutarate (2-HG) may drive cancer via targeting chromatin and DNA modifying enzymes have forced a reevaluation. Indeed, multiple metabolic intermediates can modulate chromatin modifiers, suggesting that altered metabolism may drive epigenetic changes enabling carcinogenesis. Our work has implicated a distinct mechanism, whereby metabolic reprogramming and altered chromatin promote genomic instability and cellular immortality, two hallmarks of cancer.

This work began with efforts to target the Warburg effect with small-molecule glucose uptake inhibitors. While targeting glycolysis failed to affect cell proliferation on its own, treated cells were sensitized to radiation, displaying a loss of DNA repair and increased cellular senescence. Working downstream, we found much of this effect was mediated by the hexosamine biosynthetic pathway (HBP) which brings together glucose and glutamine to produce N-acetyl glucosamine (GlcNAc) to support protein glycosylation. Thousands of nuclear, cytoplasmic and mitochondrial protein serine and threonine residues can be modified by O-GlcNAc transferase (OGT) and the resulting O-GlcNAcylation is linked to stress and DNA damage tolerance. Our data implicated the polycomb repressive complexes PRC1 and 2 and their catalytic subunits BMI1 and EZH2 as key OGT targets. Small molecule inhibitors and/or RNAi targeting the HBP, OGT, BMI1 or EZH2 similarly delayed DSB repair and induced senescence after irradiation. In light of others' work linking the histone H3 K27 methyltransferase activity of EZH2 to 53BP1 binding at DSBs to drive repair by non-homologous end-joining (NHEJ), these studies suggest a pathway from the Warburg effect to O-GlcNAcylation and rapid, error-prone DSB repair.

Working downstream to validate this mechanism, we discovered that glycolysis and the HBP balanced an antagonistic effect of the TCA cycle on DSB repair. Excess α-ketoglutarate (2-OG) serves as a cofactor for diverse dioxygenases, including the lysine demethylases (KDMs) that antagonize histone methyltransferases such as EZH2. Activating the TCA cycle or providing exogenous 2-OG blocked DSB repair after irradiation and increased senescence while inhibiting all 2-OG-dependent dioxygenases or only the KDM enzymes that remove histone modifications by EZH2 at H3 K27 or G9A at H3 K9 restored DSB repair. This led us to examine the effects of treating cells with the oncometabolite 2-HG, known to mediate its effects by serving as a 2-OG-dependent dioxygenase inhibitor. While prior attention has largely focused on TET DNA demethylases as 2-HG targets and epigenetic mechanisms for carcinogenesis, we observed 2-HG blocking KDM enzymes to accelerate error-prone NHEJ repair, suggesting a role in genomic instability in IDH mutant cells.

Toward translation, we have examined the effects of blocking O-GlcNAcylation in vivo as a means to sensitize tumors to radiation. Animals bearing tumors expressing shRNA targeting OGT or treated with OGT inhibitors and then irradiated displayed decreased protein O-GlcNAcylation, a delay in DSB repair, greater cell death, delayed cell recovery and increased senescence. In turn, when animals were treated with GlcNAc or with shRNA or inhibitors targeting O-GlcNAcase, their tumors displayed increased O-GlcNAcylation and dramatic radiation resistance, indicating accelerated DSB repair in vivo. These results implicate OGT and O-GlcNAcyation as a new mechanism by which the Warburg effect may mediate resistance to radiation therapy. Further, our studies point to dietary interventions and/or drugs targeting OGT as a route to improving outcomes from radiotherapy in the clinic.

Taken together, an implication of this work is that cancer metabolism may help drive carcinogenesis by shifting repair to NHEJ and away from HR, leading to genomic instability, as well as by overcoming barriers to transformation such as accelerated senescence to promote cell immortality. Our studies argue for renewed efforts to explore cancer metabolism as a target for prevention and therapy, with a focus on leveraging crosstalk with pathways regulating cellular responses to DNA damage.

Citation Format: Elena Efimova, Yue Liu, Julian Lutze, Tamica Collins, Amy Flor, Jacqueline Brinkman, Don Wolfgeher, Sara Warrington, Stephen J. Kron. Shutting off cancer's fountain of youth: Targeting metabolism to block repair and reverse immortality [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr SY21-03.

Reversibility of severe mitral valve regurgitation after left ventricular assist device implantation: single-centre observations from a real-life population of patients

OBJECTIVES

This study evaluates the impact of untreated preoperative severe mitral valve regurgitation (MR) on outcomes after left ventricular assist device (LVAD) implantation.

METHODS

Of the 234 patients who received LVAD therapy in our centre during a 6-year period, we selected those who had echocardiographic images of good quality and excluded those who underwent mitral valve replacement prior to or mitral valve repair during LVAD placement. The 128 patients selected were divided into 2 groups: Group A with severe MR (n = 65) and Group B with none to moderate MR (n = 63, 28 with moderate MR). We evaluated transthoracic echocardiography preoperatively [15 (7-28) days before LVAD implantation; median (interquartile range)] and postoperatively up to the last available follow-up [501 (283-848) days after LVAD]. We collected mortality, complications and clinical status indicators of the patient cohort.

RESULTS

We observed a significant decrease in the severity of MR after LVAD implantation (severe MR 51% pre- vs 6% post-LVAD implantation, P < 0.001). There was no difference between groups in terms of right heart failure, rate of urgent heart transplantation, pump thrombosis or ventricular arrhythmias. There was no difference in 1-year survival and 3-year survival (87.7% vs 88.4% and 71.8% vs 66.6% for Groups A and B, respectively, P = 0.97).

CONCLUSIONS

Preoperative severe MR resolves in the majority of patients early on after LVAD implantation and is not associated with worse clinical outcomes or intermediate-term survival.

Dynamic decoupling of biomass and wax ester biosynthesis in Acinetobacter baylyi by an autonomously regulated switch

For improving the microbial production of fuels and chemicals, gene knock-outs and overexpression are routinely applied to intensify the carbon flow from substrate to product. However, their possibilities in dynamic control of the flux between the biomass and product synthesis are limited, whereas dynamic metabolic switches can be used for optimizing the distribution of carbon and resources. The production of single cell oils is especially challenging, as the synthesis is strictly regulated, competes directly with biomass, and requires defined conditions, such as nitrogen limitation. Here, we engineered a metabolic switch for redirecting carbon flow from biomass to wax ester production in Acinetobacter baylyi ADP1 using acetate as a carbon source. Isocitrate lyase, an essential enzyme for growth on acetate, was expressed under an arabinose inducible promoter. The autonomous downregulation of the expression is based on the gradual oxidation of the arabinose inducer by a glucose dehydrogenase gcd. The depletion of the inducer, occurring simultaneously to acetate consumption, switches the cells from a biomass mode to a lipid synthesis mode, enabling the efficient channelling of carbon to wax esters in a simple batch culture. In the engineered strain, the yield and titer of wax esters were improved by 3.8 and 3.1 folds, respectively, over the control strain. In addition, the engineered strain accumulated wax esters 19% of cell dry weight, being the highest reported among microbes. The study provides important insights into the dynamic engineering of the biomass-dependent synthesis pathways for the improved production of biocompounds from low-cost and sustainable substrates.

•

Efficient conversion of acetate to storage lipids (wax ester) is demonstrated.

•

AraC-pBAD promoter coupled with glucose dehydrogenase was used as a dynamic switch.

•

The autonomous switch allowed dynamic shift from biomass to lipid synthesis mode.

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Wax ester yield and titer were improved by 3–4 folds over the wild type strain.

•

The highest amount of wax esters produced in microbes, 19% of CDW, was achieved.

Metabolic pairing of aerobic and anaerobic production in a one-pot batch cultivation

BACKGROUND

The versatility of microbial metabolic pathways enables their utilization in vast number of applications. However, the electron and carbon recovery rates, essentially constrained by limitations of cell energetics, are often too low in terms of process feasibility. Cocultivation of divergent microbial species in a single process broadens the metabolic landscape, and thus, the possibilities for more complete carbon and energy utilization.

RESULTS

In this study, we integrated the metabolisms of two bacteria, an obligate anaerobe Clostridium butyricum and an obligate aerobe Acinetobacter baylyi ADP1. In the process, a glucose-negative mutant of A. baylyi ADP1 first deoxidized the culture allowing C. butyricum to grow and produce hydrogen from glucose. In the next phase, ADP1 produced long chain alkyl esters (wax esters) utilizing the by-products of C. butyricum, namely acetate and butyrate. The coculture produced 24.5 ± 0.8 mmol/l hydrogen (1.7 ± 0.1 mol/mol glucose) and 28 mg/l wax esters (10.8 mg/g glucose).

CONCLUSIONS

The cocultivation of strictly anaerobic and aerobic bacteria allowed the production of both hydrogen gas and long-chain alkyl esters in a simple one-pot batch process. The study demonstrates the potential of 'metabolic pairing' using designed microbial consortia for more optimal electron and carbon recovery.

[Recognizing rare cardiac diseases by electrocardiogram]

A number of rare cardiac diseases can be recognized by electrocardiogram (ECG). This article illustrates the clinical importance of ECG as a key diagnostic tool to detect Wolff-Parkinson-White syndrome and channelopathies, which are frequently diagnosed late after one or more affected family members have become victims of sudden cardiac death. These channelopathies include long QT syndrome, short QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia. In addition, typical ECG findings are frequently present in patients with idiopathic ventricular tachycardia, arrhythmogenic right ventricular dysplasia, digitalis intoxication, hyperkalemia, acute cor pulmonale due to pulmonary embolism, as well as severe left ventricular hypertrophy as in hypertrophic cardiomyopathy.

Improved fatty aldehyde and wax ester production by overexpression of fatty acyl-CoA reductases

Background

Fatty aldehydes are industrially relevant compounds, which also represent a common metabolic intermediate in the microbial synthesis of various oleochemicals, including alkanes, fatty alcohols and wax esters. The key enzymes in biological fatty aldehyde production are the fatty acyl-CoA/ACP reductases (FARs) which reduce the activated acyl molecules to fatty aldehydes. Due to the disparity of FARs, identification and in vivo characterization of reductases with different properties are needed for the construction of tailored synthetic pathways for the production of various compounds.

Results

Fatty aldehyde production in Acinetobacter baylyi ADP1 was increased by the overexpression of three different FARs: a native A. baylyi FAR Acr1, a cyanobacterial Aar, and a putative, previously uncharacterized dehydrogenase (Ramo) from Nevskia ramosa. The fatty aldehyde production was followed in real-time inside the cells with a luminescence-based tool, and the highest aldehyde production was achieved with Aar. The fate of the overproduced fatty aldehydes was studied by measuring the production of wax esters by a native downstream pathway of A. baylyi, for which fatty aldehyde is a specific intermediate. The wax ester production was improved with the overexpression of Acr1 or Ramo compared to the wild type A. baylyi by more than two-fold, whereas the expression of Aar led to only subtle wax ester production. The overexpression of FARs did not affect the length of the acyl chains of the wax esters.

Conclusions

The fatty aldehyde production, as well as the wax ester production of A. baylyi, was improved with the overexpression of a key enzyme in the pathway. The wax ester titer (0.45 g/l) achieved with the overexpression of Acr1 is the highest reported without hydrocarbon supplementation to the culture. The contrasting behavior of the different reductases highlight the significance of in vivo characterization of enzymes and emphasizes the possibilities provided by the diversity of FARs for pathway and product modulation.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-0869-z) contains supplementary material, which is available to authorized users.

Production of long chain alkyl esters from carbon dioxide and electricity by a two-stage bacterial process

Microbial electrosynthesis (MES) is a promising technology for the reduction of carbon dioxide into value-added multicarbon molecules. In order to broaden the product profile of MES processes, we developed a two-stage process for microbial conversion of carbon dioxide and electricity into long chain alkyl esters. In the first stage, the carbon dioxide is reduced to organic compounds, mainly acetate, in a MES process by Sporomusa ovata. In the second stage, the liquid end-products of the MES process are converted to the final product by a second microorganism, Acinetobacter baylyi in an aerobic bioprocess. In this proof-of-principle study, we demonstrate for the first time the bacterial production of long alkyl esters (wax esters) from carbon dioxide and electricity as the sole sources of carbon and energy. The process holds potential for the efficient production of carbon-neutral chemicals or biofuels.

Myocardial voltage ratio in arrhythmogenic right ventricular dysplasia/cardiomyopathy

AIMS

This study aimed to analyze the influence of scar distribution between the endocardium and the epicardium in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C).

METHODS

Electroanatomical mapping data were derived from our ARVD/C registry. Myocardial voltage distribution between the endocardium and the epicardium was analyzed in 28 patients (18 men, 49.9 ± 13.0 years) with previous ventricular tachycardia (VT) ablation and complete right ventricular maps.

RESULTS

During the follow-up period of 28 ± 22 months after ablation, 18 of 28 patients (64.3%) remained free from VT recurrence. In univariate analysis, five variables associated with VT recurrence, i. e., advanced age, right ventricular (RV) myocardial voltage ratio ≥0.58, inducibility of VT after ablation, and longer procedure and fluoroscopy time. In binary logistic regression analysis only RV myocardial voltage ratio ≥0.58 (hazard ratio 11.667, 95% confidence interval 1.487-91.543, p = 0.012) remained associated with an increased risk of VT recurrence.

CONCLUSION

The myocardial voltage ratio (bipolar low voltage area/unipolar low voltage area) as a potential surrogate parameter for scar distribution between the endocardium and the epicardium is significantly associated with the outcome after VT ablation in ARVD/C.

Growth and wax ester production of an Acinetobacter baylyi ADP1 mutant deficient in exopolysaccharide capsule synthesis

Acinetobacter baylyi ADP1 naturally produces wax esters that could be used as a raw material in industrial applications. We attempted to improve wax ester yield of A. baylyi ADP1 by removing rmlA, a gene involved in exopolysaccharide production. Growth rate, biomass formation and wax ester yield on 4-hydroxybenzoate were not affected, but the rmlA− strain grew slower on acetate, while reaching similar biomass and wax ester yield. The rmlA− cells had malformed shape and large size and grew poorly on glucose without expression of the gene for pyruvate kinase (pykF) from Escherichia coli. The pykF-expressing rmlA− strain had similar growth rate, lowered biomass formation and improved wax ester production on glucose as compared to the wild-type strain expressing pykF. Cultivation of the pykF-expressing rmlA− strain on an elevated glucose concentration in a medium supplemented with amino acids resulted in doubled molar wax ester yield and acetate production.

Differentiating the origin of outflow tract ventricular arrhythmia using a simple, novel approach

BACKGROUND

Numerous electrocardiographic (ECG) criteria have been proposed to identify localization of outflow tract ventricular arrhythmias (OT-VAs); however, in some cases, it is difficult to accurately localize the origin of OT-VA using the surface ECG.

OBJECTIVE

The purpose of this study was to assess a simple criterion for localization of OT-VAs during electrophysiology study.

METHODS

We measured the interval from the onset of the earliest QRS complex of premature ventricular contractions (PVCs) to the distal right ventricular apical signal (the QRS-RVA interval) in 66 patients (31 men aged 53.3 ± 14.0 years; right ventricular outflow tract [RVOT] origin in 37) referred for ablation of symptomatic outflow tract PVCs. We prospectively validated this criterion in 39 patients (22 men aged 52 ± 15 years; RVOT origin in 19).

RESULTS

Compared with patients with RVOT PVCs, the QRS-RVA interval was significantly longer in patients with left ventricular outflow tract (LVOT) PVCs (70 ± 14 vs 33.4±10 ms, P < .001). Receiver operating characteristic analysis showed that a QRS-RVA interval ≥49 ms had sensitivity, specificity, and positive and negative predictive values of 100%, 94.6%, 93.5%, and 100%, respectively, for prediction of an LVOT origin. The same analysis in the validation cohort showed sensitivity, specificity, and positive and negative predictive values of 94.7%, 95%, 95%, and 94.7%, respectively. When these data were combined, a QRS-RVA interval ≥49 ms had sensitivity, specificity, and positive and negative predictive values of 98%, 94.6%, 94.1%, and 98.1%, respectively, for prediction of an LVOT origin.

CONCLUSION

A QRS-RVA interval ≥49 ms suggests an LVOT origin. The QRS-RVA interval is a simple and accurate criterion for differentiating the origin of outflow tract arrhythmia during electrophysiology study; however, the accuracy of this criterion in identifying OT-VA from the right coronary cusp is limited.

Rewiring the wax ester production pathway of Acinetobacter baylyi ADP1

Wax esters are industrially relevant high-value molecules. For sustainable production of wax esters, bacterial cell factories are suggested to replace the chemical processes exploiting expensive starting materials. However, it is well recognized that new sophisticated solutions employing synthetic biology toolbox are required to improve and tune the cellular production platform to meet the product requirements. For example, saturated wax esters with alkanol chain lengths C12 or C14 that are convenient for industrial uses are rare among bacteria. Acinetobacter baylyi ADP1, a natural producer of wax esters, is a convenient model organism for studying the potentiality and modifiability of wax esters in a natural host by means of synthetic biology. In order to establish a controllable production platform exploiting well-characterized biocomponents, and to modify the wax ester synthesis pathway of A. baylyi ADP1 in terms product quality, a fatty acid reductase complex LuxCDE with an inducible arabinose promoter was employed to replace the natural fatty acyl-CoA reductase acr1 in ADP1. The engineered strain was able to produce wax esters by the introduced synthetic pathway. Moreover, the fatty alkanol chain length profile of wax esters was found to shift toward shorter and more saturated carbon chains, C16:0 accounting for most of the alkanols. The study demonstrates the potentiality of recircuiting a biosynthesis pathway in a natural producer, enabling a regulated production of a customized bioproduct. Furthermore, the LuxCDE complex can be potentially used as a well-characterized biopart in a variety of synthetic biology applications involving the production of long-chain hydrocarbons.

Abstract 1769: Real-time imaging demonstrates cancer cells exposed to UV irradiation either repair their DNA or die

The DNA repair protein 53BP1 is re-localized in foci after DNA damage. In this study, we imaged the real-time response of 53BP1 linked to GFP to DNA damage induced by UV irradiation. Inhibition of proliferation by UV irradiation was analyzed by a clonogenic assay. The relocalization of GFP fused to the chromatin-binding domain of 53BP1 was imaged after UV irradiation of MiaPaca-2 53BP1-GFP human pancreatic cancer cells. The clonogenic assay demonstrated that UVC dose-dependently inhibited cell proliferation, while UVA and UVB showed little effect. During live-cell imaging, 53BP1-GFP foci formation was observed within 30 min after UVC irradiation. High-dose UVC also induced apoptosis within 24 h after irradiation. The cells treated with UVC irradiation appear to have two different fates: DNA repair or apoptosis. A fraction of the cells underwent apoptosis, and the other fraction repaired their DNA as evidenced by 53BP1 focus formation. The present study demonstrates that some cells may repair their DNA successfully and others can not. This has important implication for UV-based photodynamic therapy.

Citation Format: Shinji Miwa, Shuya Yano, Yukihiko Hiroshima, Yasunori Tome, Fuminori Uehara, Sumiyuki Mii, Hiroaki Kimura, Katsuro Hayashi, Hiroyuki Tsuchiya, Elena Efimova, Michelle Digman, Enrico Gratton, Robert M. Hoffman. Real-time imaging demonstrates cancer cells exposed to UV irradiation either repair their DNA or die. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1769. doi:10.1158/1538-7445.AM2013-1769

Lipid profile characterization of wastewaters from different origins

Lipids in wastewaters are potential raw material for renewable diesel, but may complicate biological treatment of wastewaters. The lipid composition of palm oil mill effluent (POME), chemithermomechanical pulp mill (CTMP) wastewater and municipal wastewater (MWW) was studied with a combination of thin-layer chromatography and nuclear magnetic resonance. Gravimetrically determined content of extracted lipids from the solids of POME and CTMP wastewater were 8.4 ± 1.2 g/L (19.6 ± 0.8% of dry weight) and 0.17-0.23 g/L (12.4-18.5%), respectively, while MWW contained 0.021 ± 0.002 g/L (9.3 ± 1.4%) of lipids. All lipid extracts contained mono-, di- and triacylglycerols (TAGs) and free fatty acids (FFAs). In POME, lipids were mostly TAGs (11.5 ± 0.2 μmol/10 mg of lipid extract). In CTMP and MWW lipid composition was more diverse than in POME containing also sterol derivatives and fatty acid methyl esters and the main lipids were FFAs.

Real-time monitoring of intracellular wax ester metabolism

BACKGROUND

Wax esters are industrially relevant molecules exploited in several applications of oleochemistry and food industry. At the moment, the production processes mostly rely on chemical synthesis from rather expensive starting materials, and therefore solutions are sought from biotechnology. Bacterial wax esters are attractive alternatives, and especially the wax ester metabolism of Acinetobacter sp. has been extensively studied. However, the lack of suitable tools for rapid and simple monitoring of wax ester metabolism in vivo has partly restricted the screening and analyses of potential hosts and optimal conditions.

RESULTS

Based on sensitive and specific detection of intracellular long-chain aldehydes, specific intermediates of wax ester synthesis, bacterial luciferase (LuxAB) was exploited in studying the wax ester metabolism in Acinetobacter baylyi ADP1. Luminescence was detected in the cultivation of the strain producing wax esters, and the changes in signal levels could be linked to corresponding cell growth and wax ester synthesis phases.

CONCLUSIONS

The monitoring system showed correlation between wax ester synthesis pattern and luminescent signal. The system shows potential for real-time screening purposes and studies on bacterial wax esters, revealing new aspects to dynamics and role of wax ester metabolism in bacteria.

Improved triacylglycerol production in Acinetobacter baylyi ADP1 by metabolic engineering

Background

Triacylglycerols are used in various purposes including food applications, cosmetics, oleochemicals and biofuels. Currently the main sources for triacylglycerol are vegetable oils, and microbial triacylglycerol has been suggested as an alternative for these. Due to the low production rates and yields of microbial processes, the role of metabolic engineering has become more significant. As a robust model organism for genetic and metabolic studies, and for the natural capability to produce triacylglycerol, Acinetobacter baylyi ADP1 serves as an excellent organism for modelling the effects of metabolic engineering for energy molecule biosynthesis.

Results

Beneficial gene deletions regarding triacylglycerol production were screened by computational means exploiting the metabolic model of ADP1. Four deletions, acr1, poxB, dgkA, and a triacylglycerol lipase were chosen to be studied experimentally both separately and concurrently by constructing a knock-out strain (MT) with three of the deletions. Improvements in triacylglycerol production were observed: the strain MT produced 5.6 fold more triacylglycerol (mg/g cell dry weight) compared to the wild type strain, and the proportion of triacylglycerol in total lipids was increased by 8-fold.

Conclusions

In silico predictions of beneficial gene deletions were verified experimentally. The chosen single and multiple gene deletions affected beneficially the natural triacylglycerol metabolism of A. baylyi ADP1. This study demonstrates the importance of single gene deletions in triacylglycerol metabolism, and proposes Acinetobacter sp. ADP1 as a model system for bioenergetic studies regarding metabolic engineering.

Behavioral impact of the regulation of the brain 2-oxoglutarate dehydrogenase complex by synthetic phosphonate analog of 2-oxoglutarate: implications into the role of the complex in neurodegenerative diseases

Decreased activity of the mitochondrial 2-oxoglutarate dehydrogenase complex (OGDHC) in brain accompanies neurodegenerative diseases. To reveal molecular mechanisms of this association, we treated rats with a specific inhibitor of OGDHC, succinyl phosphonate, or exposed them to hypoxic stress. In males treated with succinyl phosphonate and in pregnancy-sensitized females experiencing acute hypobaric hypoxia, we revealed upregulation of brain OGDHC (within 24 hours), with the activity increase presumably representing the compensatory response of brain to the OGDHC inhibition. This up-regulation of brain OGDHC was accompanied by an increase in exploratory activity and a decrease in anxiety of the experimental animals. Remarkably, the hypoxia-induced elevation of brain OGDHC and most of the associated behavioral changes were abrogated by succinyl phosphonate. The antagonistic action of hypoxia and succinyl phosphonate demonstrates potential therapeutic significance of the OGDHC regulation by the phosphonate analogs of 2-oxoglutarate.

Thermophilic biohydrogen production by an anaerobic heat treated-hot spring culture

Batch experiments were conducted to investigate the thermophilic biohydrogen production using an enrichment culture from a Turkish hot spring. Following the enrichment, the culture was heat treated at 100 degrees C for 10 min to select for spore-forming bacteria. H(2) production was accompanied by production of acetate, butyrate, lactate and ethanol. H(2) production was associated by acetate-butyrate type fermentation while accumulation of lactate and ethanol negatively affected the H(2) yield. H(2) production was highest in the temperature range from 49.6 to 54.8 degrees C and optimum values for initial pH and concentrations of iron, yeast extract and glucose were 6.5, 40 mg/l, 4-13.5 g/l, respectively. PCR-DGGE profiling showed that the heat treated culture consisted of species closely affiliated to genus Thermoanaerobacterium.

Neutron diffraction studies of structural and magnetic properties of niobium doped cobaltites

Neutron powder diffraction studies of the structural and magnetic properties of the La(1-x)Sr(x)Nb(y)Co(1-y)O(3) solid solutions (x = 0.2, 0.5; y = 0, 0.075, 0.1) have been performed. Substitution of Co(2+) by Nb(5+) prevents the formation of Co(4+) and leads to stabilization of the Co(3+) ions in the high- or intermediate-spin state. This is accompanied by the significant change of the Co-O bond length as well as Co-O-Co bond angle in the CoO(6) octahedron. The obtained data are in agreement with the negative sign of the magnetic exchange interactions Co(3+)-O-Co(3+) in a relatively wide range of the Co-O-Co bond angles. Diamagnetic dilution by the niobium ions prevents long-range magnetic ordering and strongly increases magnetoresistance at low temperature.

IG20, a MADD splice variant, increases cell susceptibility to gamma-irradiation and induces soluble mediators that suppress tumor cell growth

The IG20 gene encodes at least four splice variants, including DENN-SV and IG20. DENN-SV is constitutively expressed at higher levels in tumor tissues. Cells transfected with the DENN-SV cDNA show increased resistance to tumor necrosis factor alpha (TNFalpha), TNF-related apoptosis-inducing ligand (TRAIL), etoposide, and vinblastine treatment, whereas overexpression of IG20 enhanced susceptibility to both intrinsic (drugs) and extrinsic (e.g., TNFalpha and TRAIL) death signals. In this study, we investigated whether expression of the IG20 can render cells susceptible to gamma-irradiation. Consistent with previous results, overexpression of DENN-SV and IG20 in HeLa cells conferred resistance and susceptibility, respectively, to the effects of gamma-irradiation. HeLa IG20 cell susceptibility was attributable to enhanced apoptosis and reduced cell growth. This growth suppression was mediated by secreted soluble factors. Although HeLa DENN-SV cells grew more rapidly than control cells, replenishment with conditioned media from HeLa IG20 cells suppressed their growth. In addition, the conditioned media from HeLa IG20 cells stopped the growth of ovarian PA-1 cancer cells in the G(1)-G(0) cell cycle stage. Among an array of cytokines tested, interleukin 6 (IL-6) was found at the highest levels in HeLa IG20 culture supernatants, and IL-6 neutralization showed that it was, in part, responsible for the cell growth suppression. HeLa IG20 cells had elevated basal nuclear factor kappaB levels, a known regulator of IL-6 transcription. Finally, IG20 overexpression enhanced the combined apoptotic effects of TRAIL and gamma-irradiation on HeLa cells. These results suggest that understanding further the mechanism of action of the IG20 splice variant may help in the advancement of cancer therapies.

Nrf2 is an inhibitor of the Fas pathway as identified by Achilles' Heel Method, a new function-based approach to gene identification in human cells

Here we describe the Achilles' Heel Method (AHM), a new function-based approach for identification of inhibitors of signaling pathways, optimized for human cells. The principle of AHM is the identification of 'sensitizing' cDNAs based on their decreased abundance following selection. As a proof of principle, we have employed AHM for the identification of Fas/CD95/APO-1 pathway inhibitors. HeLa cells were transfected with an antisense cDNA expression library in an episomal vector followed by selection with a suboptimal dose of the apoptotic inducer. Antisense inactivation of Fas inhibitors rendered the cells more sensitive to apoptosis resulting in their preferential death and consequent loss of their sensitizing episomes that were identified by subtraction. We show that the resulting products were enriched for sensitizing cDNAs as seven out of eight candidates tested were confirmed as inhibitors of Fas-induced killing either by transfection or by pharmacological inhibition. Furthermore, we demonstrate by multiple approaches that one candidate, NF-E2 related factor 2 (Nrf2), is an inhibitor of Fas-induced apoptosis. Inactivation of Nrf2 by antisense or by a membrane permeable dominant-negative polypeptide sensitized cells while overexpression of Nrf2 protected cells from Fas-induced apoptosis. In addition, dicumarol, an inhibitor of the phase II detoxifying enzyme NQO1, a downstream target of Nrf2, sensitized cells. Nrf2 induces the production of Glutathione (GSH) and we demonstrated that N-acetyl L-cysteine (NAC), a precursor to GSH, protected cells from Fas-mediated killing. Taken together, AHM is a powerful approach for the identification of inhibitors of a signaling pathway with a low rate of false positives that opens new avenues for function profiling of human genes and discovery of new drug targets.