scholarly journals Functional dissection and modulation of the BirA protein for improved autotrophic growth of gas‐fermenting Clostridium ljungdahlii

2021 ◽  
Author(s):  
Can Zhang ◽  
Xiaoqun Nie ◽  
Huan Zhang ◽  
Yuwei Wu ◽  
Huiqi He ◽  
...  
Keyword(s):  
Autotrophic Growth ◽  
Clostridium Ljungdahlii

scholarly journals The Rnf Complex of Clostridium ljungdahlii Is a Proton-Translocating Ferredoxin:NAD+ Oxidoreductase Essential for Autotrophic Growth

mBio ◽  
2012 ◽  
Vol 4 (1) ◽  
Author(s):  
Pier-Luc Tremblay ◽  
Tian Zhang ◽  
Shabir A. Dar ◽  
Ching Leang ◽  
Derek R. Lovley
Keyword(s):  
Energy Conservation ◽  
Atp Synthesis ◽  
Proton Motive Force ◽  
Motive Force ◽  
Proton Gradient ◽  
Heterotrophic Growth ◽  
Deficient Mutant ◽  
Autotrophic Growth ◽  
Content Type ◽  
Clostridium Ljungdahlii

ABSTRACTIt has been predicted that the Rnf complex ofClostridium ljungdahliiis a proton-translocating ferredoxin:NAD+oxidoreductase which contributes to ATP synthesis by an H+-translocating ATPase under both autotrophic and heterotrophic growth conditions. The recent development of methods for genetic manipulation ofC. ljungdahliimade it possible to evaluate the possible role of the Rnf complex in energy conservation. Disruption of theC. ljungdahlii rnfoperon inhibited autotrophic growth. ATP synthesis, proton gradient, membrane potential, and proton motive force collapsed in the Rnf-deficient mutant with H2as the electron source and CO2as the electron acceptor. Heterotrophic growth was hindered in the absence of a functional Rnf complex, as ATP synthesis, proton gradient, and proton motive force were significantly reduced with fructose as the electron donor. Growth of the Rnf-deficient mutant was also inhibited when no source of fixed nitrogen was provided. These results demonstrate that the Rnf complex ofC. ljungdahliiis responsible for translocation of protons across the membrane to elicit energy conservation during acetogenesis and is a multifunctional device also implicated in nitrogen fixation.IMPORTANCEMechanisms for energy conservation in the acetogenClostridium ljungdahliiare of interest because of its potential value as a chassis for the production of biocommodities with novel electron donors such as carbon monoxide, syngas, and electrons derived from electrodes. Characterizing the components implicated in the chemiosmotic ATP synthesis during acetogenesis byC. ljungdahliiis a prerequisite for the development of highly productive strains. The Rnf complex has been considered the prime candidate to be the pump responsible for the formation of an ion gradient coupled with ATP synthesis in multiple acetogens. However, experimental evidence for a proton-pumping Rnf complex has been lacking. This study establishes theC. ljungdahliiRnf complex as a proton-translocating ferredoxin:NAD+oxidoreductase and demonstrates thatC. ljungdahliihas the potential of becoming a model organism to study proton translocation, electron transport, and other functions of the Rnf complex in energy conservation or other processes.

scholarly journals Metabolic engineering of Moorella thermoacetica for thermophilic bioconversion of gaseous substrates to a volatile chemical

AMB Express ◽  
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Junya Kato ◽  
Kaisei Takemura ◽  
Setsu Kato ◽  
Tatsuya Fujii ◽  
Keisuke Wada ◽  
...  
Keyword(s):  
Carbon Flux ◽  
Cost Effective ◽  
Gas Composition ◽  
Autotrophic Growth ◽  
Acetyl Coenzyme A ◽  
Volatile Chemicals ◽  
Moorella Thermoacetica ◽  
Gas Fermentation ◽  
Dry Cell ◽  
Co Gas

AbstractGas fermentation is one of the promising bioprocesses to convert CO2 or syngas to important chemicals. Thermophilic gas fermentation of volatile chemicals has the potential for the development of consolidated bioprocesses that can simultaneously separate products during fermentation. This study reports the production of acetone from CO2 and H2, CO, or syngas by introducing the acetone production pathway using acetyl–coenzyme A (Ac-CoA) and acetate produced via the Wood–Ljungdahl pathway in Moorella thermoacetica. Reducing the carbon flux from Ac-CoA to acetate through genetic engineering successfully enhanced acetone productivity, which varied on the basis of the gas composition. The highest acetone productivity was obtained with CO–H2, while autotrophic growth collapsed with CO2–H2. By adding H2 to CO, the acetone productivity from the same amount of carbon source increased compared to CO gas only, and the maximum specific acetone production rate also increased from 0.04 to 0.09 g-acetone/g-dry cell/h. Our development of the engineered thermophilic acetogen M. thermoacetica, which grows at a temperature higher than the boiling point of acetone (58 °C), would pave the way for developing a consolidated process with simplified and cost-effective recovery via condensation following gas fermentation.

scholarly journals Lactose-Inducible System for Metabolic Engineering of Clostridium ljungdahlii

2014 ◽  
Vol 80 (8) ◽  
pp. 2410-2416 ◽  
Author(s):  
Areen Banerjee ◽  
Ching Leang ◽  
Toshiyuki Ueki ◽  
Kelly P. Nevin ◽  
Derek R. Lovley
Keyword(s):  
Ethanol Production ◽  
Genetic Manipulation ◽  
Electron Flow ◽  
Model Organism ◽  
Inducible Expression ◽  
Carbon Flow ◽  
Wild Type ◽  
Content Type ◽  
Microbial Electrosynthesis ◽  
Clostridium Ljungdahlii

ABSTRACTThe development of tools for genetic manipulation ofClostridium ljungdahliihas increased its attractiveness as a chassis for autotrophic production of organic commodities and biofuels from syngas and microbial electrosynthesis and established it as a model organism for the study of the basic physiology of acetogenesis. In an attempt to expand the genetic toolbox forC. ljungdahlii, the possibility of adapting a lactose-inducible system for gene expression, previously reported forClostridium perfringens, was investigated. The plasmid pAH2, originally developed forC. perfringenswith agusAreporter gene, functioned as an effective lactose-inducible system inC. ljungdahlii. Lactose induction ofC. ljungdahliicontaining pB1, in which the gene for the aldehyde/alcohol dehydrogenase AdhE1 was downstream of the lactose-inducible promoter, increased expression ofadhE130-fold over the wild-type level, increasing ethanol production 1.5-fold, with a corresponding decrease in acetate production. Lactose-inducible expression ofadhE1in a strain in whichadhE1and theadhE1homologadhE2had been deleted from the chromosome restored ethanol production to levels comparable to those in the wild-type strain. Inducing expression ofadhE2similarly failed to restore ethanol production, suggesting thatadhE1is the homolog responsible for ethanol production. Lactose-inducible expression of the four heterologous genes necessary to convert acetyl coenzyme A (acetyl-CoA) to acetone diverted ca. 60% of carbon flow to acetone production during growth on fructose, and 25% of carbon flow went to acetone when carbon monoxide was the electron donor. These studies demonstrate that the lactose-inducible system described here will be useful for redirecting carbon and electron flow for the biosynthesis of products more valuable than acetate. Furthermore, this tool should aid in optimizing microbial electrosynthesis and for basic studies on the physiology of acetogenesis.

scholarly journals Metagenomics-guided analysis of microbial chemolithoautotrophic phosphite oxidation yields evidence of a seventh natural CO2fixation pathway

2017 ◽  
Vol 115 (1) ◽  
pp. E92-E101 ◽  
Author(s):  
Israel A. Figueroa ◽  
Tyler P. Barnum ◽  
Pranav Y. Somasekhar ◽  
Charlotte I. Carlström ◽  
Anna L. Engelbrektson ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
16S Rrna ◽  
Carbon Fixation ◽  
Community Analysis ◽  
Metabolic Model ◽  
Rrna Gene ◽  
Autotrophic Growth ◽  
Anaerobic Wastewater Treatment ◽  
Natural Carbon ◽  
Environmental Relevance

Dissimilatory phosphite oxidation (DPO), a microbial metabolism by which phosphite (HPO32−) is oxidized to phosphate (PO43−), is the most energetically favorable chemotrophic electron-donating process known. Only one DPO organism has been described to date, and little is known about the environmental relevance of this metabolism. In this study, we used 16S rRNA gene community analysis and genome-resolved metagenomics to characterize anaerobic wastewater treatment sludge enrichments performing DPO coupled to CO2reduction. We identified an uncultivated DPO bacterium,CandidatusPhosphitivorax (Ca.P.) anaerolimi strain Phox-21, that belongs to candidate order GW-28 within theDeltaproteobacteria, which has no known cultured isolates. Genes for phosphite oxidation and for CO2reduction to formate were found in the genome ofCa.P. anaerolimi, but it appears to lack any of the known natural carbon fixation pathways. These observations led us to propose a metabolic model for autotrophic growth byCa.P. anaerolimi whereby DPO drives CO2reduction to formate, which is then assimilated into biomass via the reductive glycine pathway.

scholarly journals Comparison of Conventional and Novel Pre-treatment Methods for Bioethanol Production from Fruit and Vegetable Wastes

2020 ◽  
Vol 33 (4) ◽  
pp. 471-483
Author(s):  
Tugba Keskin
Keyword(s):  
Saccharomyces Cerevisiae ◽  
The Other ◽  
Yeast Fermentation ◽  
Bioethanol Production ◽  
Fruit And Vegetable ◽  
Bacterial Fermentation ◽  
Waste Gas ◽  
Clostridium Ljungdahlii ◽  
Vegetable Wastes ◽  
Pre Treatment

In this study, novel and conventional techniques for the production of bioethanol from fruit and vegetable wastes (FVWs) by yeast and bacterial fermentation were investigated experimentally. Different pretreatment techniques (acid, heat, acid/heat, and microwave) for yeast fermentation were compared. Maximum ethanol concentrations of 11.7 and 11.8 g L–1 were observed from acid/heat and microwave pretreatment, respectively, by using Saccharomyces cerevisiae. On the other hand, biochar production from FVWs and syngas fermentation from the waste gas of this process were integrated. From waste gas with 12 % CO content, 5.5 g L–1 and 2.5 g L–1 ethanol production was observed by using anaerobic mixed culture and Clostridium ljungdahlii, respectively. The overall results emphasize the potential of bioethanol production from FVWs by economically feasible and environmentally friendly methods.

scholarly journals A Heterodimeric Reduced-Ferredoxin-Dependent Methylenetetrahydrofolate Reductase from Syngas-Fermenting Clostridium ljungdahlii

2021 ◽  
Author(s):  
Jihong Yi ◽  
Haiyan Huang ◽  
Jiyu Liang ◽  
Rufei Wang ◽  
Ziyong Liu ◽  
...  
Keyword(s):  
Methylenetetrahydrofolate Reductase ◽  
Environmental Benefits ◽  
Steel Mill ◽  
Domestic Waste ◽  
Content Type ◽  
Waste Gas ◽  
Clostridium Ljungdahlii ◽  
Main Component ◽  
Mill Waste

Syngas, a mixture of CO, CO 2 , and H 2 , is the main component of steel mill waste gas and also can be generated by the gasification of biomass and urban domestic waste. Its fermentation to biofuels and biocommodities has attracted attention due to the economic and environmental benefits of this process. Clostridium ljungdahlii is one of the superior acetogens used in the technology.

scholarly journals Identification and molecular characterization of a Chlamydomonas reinhardtii mutant that shows a light intensity dependent progressive chlorophyll deficiency

F1000Research ◽  
2013 ◽  
Vol 2 ◽  
pp. 142
Author(s):  
Phillip B Grovenstein ◽  
Darryel A Wilson ◽  
Kathryn D Lankford ◽  
Kelsey A Gaston ◽  
Surangi Perera ◽  
...  
Keyword(s):  
Light Intensity ◽  
Insertional Mutagenesis ◽  
Protoporphyrin Ix ◽  
Model Organism ◽  
Genomic Region ◽  
Oxygenic Photosynthesis ◽  
Autotrophic Growth ◽  
Wild Type ◽  
Light Intensities ◽  
In The Wild

The green micro-alga Chlamydomonas reinhardtii is an elegant model organism to study all aspects of oxygenic photosynthesis. Chlorophyll (Chl) and heme are major tetrapyrroles that play an essential role in energy metabolism in photosynthetic organisms. These tetrapyrroles are synthesized via a common branched pathway that involves mainly nuclear encoded enzymes. One of the enzymes in the pathway is Mg chelatase (MgChel) which inserts Mg2+ into protoporphyrin IX (PPIX, proto) to form Magnesium-protoporphyrin IX (MgPPIX, Mgproto), the first biosynthetic intermediate in the Chl branch. The GUN4 (genomes uncoupled 4) protein is not essential for the MgChel activity but has been shown to significantly stimulate its activity. We have isolated a light sensitive mutant, 6F14, by random DNA insertional mutagenesis. 6F14 cannot tolerate light intensities higher than 90-100 μmol photons m-2 s-1. It shows a light intensity dependent progressive photo-bleaching. 6F14 is incapable of photo-autotrophic growth under light intensity higher than 100 μmol photons m-2 s-1. PCR based analyses show that in 6F14 the insertion of the plasmid outside the GUN4 locus has resulted in a genetic rearrangement of the GUN4 gene and possible deletions in the genomic region flanking the GUN4 gene. Our gun4 mutant has a Chl content very similar to that in the wild type in the dark and is very sensitive to fluctuations in the light intensity in the environment unlike the earlier identified Chlamydomonas gun4 mutant. Complementation with a functional copy of the GUN4 gene restored light tolerance, Chl biosynthesis and photo-autotrophic growth under high light intensities in 6F14. 6F14 is the second gun4 mutant to be identified in C. reinhardtii. Additionally, we show that our two gun4 complements over-express the GUN4 protein and show a higher Chl content per cell compared to that in the wild type strain.

Investigation of the diversity of homoacetogenic bacteria in mesophilic and thermophilic anaerobic sludges using the formyltetrahydrofolate synthetase gene

2008 ◽  
Vol 57 (5) ◽  
pp. 675-680 ◽  
Author(s):  
P. Ryan ◽  
C. Forbes ◽  
E. Colleran
Keyword(s):  
Granular Sludge ◽  
Anaerobic Sludge ◽  
Heterotrophic Growth ◽  
Autotrophic Growth ◽  
Gene Encoding ◽  
Formyltetrahydrofolate Synthetase ◽  
Homoacetogenic Bacteria ◽  
Wide Range ◽  
Key Enzyme ◽  
Acetyl Coa Pathway

Homoacetogenic bacteria are strict anaerobes capable of autotrophic growth on H2/CO2 or CO, and of heterotrophic growth on a wide range of sugars, alcohols, methoxylated aromatic compounds and one carbon compounds, yielding acetate as their sole metabolic end-product. Batch activity tests on anaerobic granular sludge, using H2/CO2 as a substrate and 2-bromoethanesulfonate (BES) as a specific methanogenic inhibitor revealed that H2/CO2 conversion and concomitant acetate production commenced only after a lag period of 60–100 h. This finding suggests that the homoacetogenic population of digester sludge could be maintained by heterotrophic growth on sugars or other organic compounds, rather than by autotrophic growth on H2/CO2. In the present study, two upflow anaerobic sludge bed (UASB) reactors were operated at 37°C and 55°C for two distinct trial periods, each characterised by the application of influents designed to enrich for homoacetogenic bacteria. Specific primers designed for the amplification of the functional gene encoding formyltetrahydrofolate synthetase (FTHFS), a key enzyme in the acetyl-CoA pathway of acetogenesis, were used as a specific probe for acetogenic bacteria. The diversity of acetogens in the granular sludge cultivated in each reactor was revealed by application of FTHFS targeted PCR. Results show that biomass acetogenic composition was dependent upon the operational temperature of the reactor and the substrate supplied as influent.

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