scholarly journals Efficient anaerobic consumption of D-xylose by E. coli BL21(DE3) via xylR adaptive mutation

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Jung Min Heo ◽  
Hyun Ju Kim ◽  
Sang Jun Lee
Keyword(s):  
Consumption Rate ◽  
Xylose Isomerase ◽  
Fold Increase ◽  
Adaptive Mutation ◽  
Growth Media ◽  
Missense Mutations ◽  
Xylose Consumption ◽  
E Coli ◽  
Fermentation Technology ◽  
Xylose Transporter

Abstract Background Microorganisms can prioritize the uptake of different sugars depending on their metabolic needs and preferences. When both D-glucose and D-xylose are present in growth media, E. coli cells typically consume D-glucose first and then D-xylose. Similarly, when E. coli BL21(DE3) is provided with both D-glucose and D-xylose under anaerobic conditions, glucose is consumed first, whereas D-xylose is consumed very slowly. Results When BL21(DE3) was adaptively evolved via subculture, the consumption rate of D-xylose increased gradually. Strains JH001 and JH019, whose D-xylose consumption rate was faster, were isolated after subculture. Genome analysis of the JH001 and JH019 strains revealed that C91A (Q31K) and C740T (A247V) missense mutations in the xylR gene (which encodes the XylR transcriptional activator), respectively, controlled the expression of the xyl operon. RT-qPCR analyses demonstrated that the XylR mutation caused a 10.9-fold and 3.5-fold increase in the expression of the xylA (xylose isomerase) and xylF (xylose transporter) genes, respectively, in the adaptively evolved JH001 and JH019 strains. A C91A adaptive mutation was introduced into a new BL21(DE3) background via single-base genome editing, resulting in immediate and efficient D-xylose consumption. Conclusions Anaerobically-adapted BL21(DE3) cells were obtained through short-term adaptive evolution and xylR mutations responsible for faster D-xylose consumption were identified, which may aid in the improvement of microbial fermentation technology.

scholarly journals Efficient Anaerobic Consumption of D-xylose by E. coli BL21(DE3) via xylR Adaptive Mutation

2021 ◽  
Author(s):  
Jung Min Heo ◽  
Hyun Ju Kim ◽  
Sang Jun Lee
Keyword(s):  
Consumption Rate ◽  
Xylose Isomerase ◽  
Fold Increase ◽  
Adaptive Mutation ◽  
Growth Media ◽  
Missense Mutations ◽  
Xylose Consumption ◽  
E Coli ◽  
Fermentation Technology ◽  
Xylose Transporter

Abstract Background: Microorganisms can prioritize the uptake of different sugars depending on their metabolic needs and preferences. When both D-glucose and D-xylose are present in growth media, E. coli cells typically consume D-glucose first and then D-xylose. Similarly, when E. coli BL21(DE3) is provided with both glucose and xylose under anaerobic conditions, glucose is consumed first, whereas xylose is consumed very slowly.Results: When BL21(DE3) was adaptively evolved via subculture, the consumption rate of D-xylose increased gradually. Strains JH001 and JH019, whose D-xylose consumption rate was faster, were isolated after subculture. Genome analysis of the JH001 and JH019 strains revealed that C91A (Q31K) and C740T (A247V) missense mutations in the xylR gene (which encodes the XylR transcriptional activator), respectively, controlled the expression of the xyl operon. RT-qPCR analyses demonstrated that the XylR mutation caused a 10.9-fold and 3.5-fold increase in the expression of the xylA (xylose isomerase) and xylF (xylose transporter) genes, respectively, in the adaptively evolved JH001 and JH019 strains. A C91A adaptive mutation was introduced into a new BL21(DE3) background via single-base genome editing, resulting in immediate and efficient D-xylose consumption. Conclusions: We obtained anaerobically-adapted BL21(DE3) cells through short-term adaptive evolution and identified xylR mutations responsible for faster xylose consumption, which may facilitate the improvement of microbial fermentation technology.

Evidence That Selected Amplification of a Bacterial lac Frameshift Allele Stimulates Lac+ Reversion (Adaptive Mutation) With or Without General Hypermutability

Genetics ◽  
2002 ◽  
Vol 161 (3) ◽  
pp. 945-956 ◽  
Author(s):  
E Susan Slechta ◽  
Jing Liu ◽  
Dan I Andersson ◽  
John R Roth
Keyword(s):  
Model Selection ◽  
Direct Effect ◽  
Mutation Rate ◽  
Side Effect ◽  
Copy Number ◽  
Fold Increase ◽  
Genetic System ◽  
Adaptive Mutation ◽  
E Coli ◽  
Frameshift Mutant

Abstract In the genetic system of Cairns and Foster, a nongrowing population of an E. coli lac frameshift mutant appears to specifically accumulate Lac+ revertants when starved on medium including lactose (adaptive mutation). This behavior has been attributed to stress-induced general mutagenesis in a subpopulation of starved cells (the hypermutable state model). We have suggested that, on the contrary, stress has no direct effect on mutability but favors only growth of cells that amplify their leaky mutant lac region (the amplification mutagenesis model). Selection enhances reversion primarily by increasing the mutant lac copy number within each developing clone on the selection plate. The observed general mutagenesis is attributed to a side effect of growth with an amplification—induction of SOS by DNA fragments released from a tandem array of lac copies. Here we show that the S. enterica version of the Cairns system shows SOS-dependent general mutagenesis and behaves in every way like the original E. coli system. In both systems, lac revertants are mutagenized during selection. Eliminating the 35-fold increase in mutation rate reduces revertant number only 2- to 4-fold. This discrepancy is due to continued growth of amplification cells until some clones manage to revert without mutagenesis solely by increasing their lac copy number. Reversion in the absence of mutagenesis is still dependent on RecA function, as expected if it depends on lac amplification (a recombination-dependent process). These observations support the amplification mutagenesis model.

scholarly journals Engineering of a Xylose Metabolic Pathway in Corynebacterium glutamicum

2006 ◽  
Vol 72 (5) ◽  
pp. 3418-3428 ◽  
Author(s):  
Hideo Kawaguchi ◽  
Alain A. Vert�s ◽  
Shohei Okino ◽  
Masayuki Inui ◽  
Hideaki Yukawa
Keyword(s):  
Carbon Source ◽  
Corynebacterium Glutamicum ◽  
Xylose Isomerase ◽  
Mineral Medium ◽  
Gene Encoding ◽  
Xylose Consumption ◽  
E Coli ◽  
High Copy Number Plasmid ◽  
Sugar Mixture ◽  
Pentose Sugar

ABSTRACT The aerobic microorganism Corynebacterium glutamicum was metabolically engineered to broaden its substrate utilization range to include the pentose sugar xylose, which is commonly found in agricultural residues and other lignocellulosic biomass. We demonstrated the functionality of the corynebacterial xylB gene encoding xylulokinase and constructed two recombinant C. glutamicum strains capable of utilizing xylose by cloning the Escherichia coli gene xylA encoding xylose isomerase, either alone (strain CRX1) or in combination with the E. coli gene xylB (strain CRX2). These genes were provided on a high-copy-number plasmid and were under the control of the constitutive promoter trc derived from plasmid pTrc99A. Both recombinant strains were able to grow in mineral medium containing xylose as the sole carbon source, but strain CRX2 grew faster on xylose than strain CRX1. We previously reported the use of oxygen deprivation conditions to arrest cell replication in C. glutamicum and divert carbon source utilization towards product production rather than towards vegetative functions (M. Inui, S. Murakami, S. Okino, H. Kawaguchi, A. A. Vert�s, and H. Yukawa, J. Mol. Microbiol. Biotechnol. 7:182-196, 2004). Under these conditions, strain CRX2 efficiently consumed xylose and produced predominantly lactic and succinic acids without growth. Moreover, in mineral medium containing a sugar mixture of 5% glucose and 2.5% xylose, oxygen-deprived strain CRX2 cells simultaneously consumed both sugars, demonstrating the absence of diauxic phenomena relative to the new xylA-xylB construct, albeit glucose-mediated regulation still exerted a measurable influence on xylose consumption kinetics.

scholarly journals Development and characterization of efficient xylose utilization strains of Zymomonas mobilis

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Jiyun Lou ◽  
Jingwen Wang ◽  
Yongfu Yang ◽  
Qing Yang ◽  
Runxia LI ◽  
...  
Keyword(s):  
Recombinant Strain ◽  
Consumption Rate ◽  
Xylose Isomerase ◽  
Xylose Utilization ◽  
Rna Seq ◽  
Strain Development ◽  
Genome Resequencing ◽  
Xylose Consumption ◽  
Genes Encoding ◽  
Lignocellulosic Biofuels

Abstract Background Efficient use of glucose and xylose is a key for the economic production of lignocellulosic biofuels and biochemicals, and different recombinant strains have been constructed for xylose utilization including those using Zymomonas mobilis as the host. However, the xylose utilization efficiency still needs to be improved. In this work, the strategy of combining metabolic engineering and adaptive laboratory evolution (ALE) was employed to develop recombinant Z. mobilis strains that can utilize xylose efficiently at high concentrations, and NGS-based genome resequencing and RNA-Seq transcriptomics were performed for strains evolved after serial transfers in different media to understand the impact of xylose and differences among strains with different xylose-utilization capabilities at molecular level. Results Heterologous genes encoding xylose isomerase and xylulokinase were evaluated, which were then introduced into xylose-utilizing strain Z. mobilis 8b to enhance its capacity of xylose utilization. The results demonstrated that the effect of three xylose isomerases on xylose utilization was different, and the increase of copy number of xylose metabolism genes can improve xylose utilization. Among various recombinant strains constructed, the xylose utilization capacity of the recombinant strain 8b-RsXI-xylB was the best, which was further improved through continuous adaption with 38 transfers over 100 days in 50 g/L xylose media. The fermentation performances of the parental strain 8b, the evolved 8b-S38 strain with the best xylose utilization capability, and the intermediate strain 8b-S8 in different media were compared, and the results showed that only 8b-S38 could completely consume xylose at 50 g/L and 100 g/L concentrations. In addition, the xylose consumption rate of 8b-S38 was faster than that of 8b at different xylose concentrations from 50 to 150 g/L, and the ethanol yield increased by 16 ~ 40%, respectively. The results of the mixed-sugar fermentation also demonstrated that 8b-S38 had a higher xylose consumption rate than 8b, and its maximum ethanol productivity was 1.2 ~ 1.4 times higher than that of 8b and 8b-S8. Whole-genome resequencing identified three common genetic changes in 8b-S38 compared with 8b and 8b-S8. RNA-Seq study demonstrated that the expression levels of genes encoding chaperone proteins, ATP-dependent proteases, phage shock proteins, ribosomal proteins, flagellar operons, and transcriptional regulators were significantly increased in xylose media in 8b-S38. The up-regulated expression of these genes may therefore contribute to the efficient xylose utilization of 8b-S38 by maintaining the normal cell metabolism and growth, repairing cellular damages, and rebalancing cellular energy to help cells resist the stressful environment. Conclusions This study provides gene candidates to improve xylose utilization, and the result of expressing an extra copy of xylose isomerase and xylulokinase improved xylose utilization also provides a direction for efficient xylose-utilization strain development in other microorganisms. In addition, this study demonstrated the necessity to combine metabolic engineering and ALE for industrial strain development. The recombinant strain 8b-S38 can efficiently metabolize xylose for ethanol fermentation at high xylose concentrations as well as in mixed sugars of glucose and xylose, which could be further developed as the microbial biocatalyst for the production of lignocellulosic biofuels and biochemicals.

scholarly journals Regulating General Mutation Rates: Examination of the Hypermutable State Model for Cairnsian Adaptive Mutation

Genetics ◽  
2003 ◽  
Vol 163 (4) ◽  
pp. 1483-1496 ◽  
Author(s):  
John R Roth ◽  
Eric Kofoid ◽  
Frederick P Roth ◽  
Otto G Berg ◽  
Jon Seger ◽  
...  
Keyword(s):  
Fold Increase ◽  
Genetic System ◽  
Selective Advantage ◽  
State Model ◽  
Adaptive Mutation ◽  
E Coli ◽  
Term Evolution ◽  
Mutation System ◽  
Response To Stress

Abstract In the lac adaptive mutation system of Cairns, selected mutant colonies but not unselected mutant types appear to arise from a nongrowing population of Escherichia coli. The general mutagenesis suffered by the selected mutants has been interpreted as support for the idea that E. coli possesses an evolved (and therefore beneficial) mechanism that increases the mutation rate in response to stress (the hypermutable state model, HSM). This mechanism is proposed to allow faster genetic adaptation to stressful conditions and to explain why mutations appear directed to useful sites. Analysis of the HSM reveals that it requires implausibly intense mutagenesis (105 times the unselected rate) and even then cannot account for the behavior of the Cairns system. The assumptions of the HSM predict that selected revertants will carry an average of eight deleterious null mutations and thus seem unlikely to be successful in long-term evolution. The experimentally observed 35-fold increase in the level of general mutagenesis cannot account for even one Lac+ revertant from a mutagenized subpopulation of 105 cells (the number proposed to enter the hypermutable state). We conclude that temporary general mutagenesis during stress is unlikely to provide a long-term selective advantage in this or any similar genetic system.

Potentiation by L-cysteine of the bactericidal effect of hydrogen peroxide in Escherichia coli

1982 ◽  
Vol 152 (1) ◽  
pp. 81-88
Author(s):  
E H Berglin ◽  
M B Edlund ◽  
G K Nyberg ◽  
J Carlsson
Keyword(s):  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Metal Ion ◽  
Chelating Agent ◽  
Fold Increase ◽  
Bactericidal Effect ◽  
Anaerobic Conditions ◽  
Dna Breakage ◽  
E Coli ◽  
K 12

Under anaerobic conditions an exponentially growing culture of Escherichia coli K-12 was exposed to hydrogen peroxide in the presence of various compounds. Hydrogen peroxide (0.1 mM) together with 0.1 mM L-cysteine or L-cystine killed the organisms more rapidly than 10 mM hydrogen peroxide alone. The exposure of E. coli to hydrogen peroxide in the presence of L-cysteine inhibited some of the catalase. This inhibition, however, could not fully explain the 100-fold increase in hydrogen peroxide sensitivity of the organism in the presence of L-cysteine. Of other compounds tested only some thiols potentiated the bactericidal effect of hydrogen peroxide. These thiols were effective, however, only at concentrations significantly higher than 0.1 mM. The effect of L-cysteine and L-cystine could be annihilated by the metal ion chelating agent 2,2'-bipyridyl. DNA breakage in E. coli K-12 was demonstrated under conditions where the organisms were killed by hydrogen peroxide.

scholarly journals Dynamic regulation of extracellular ATP in Escherichia coli

2017 ◽  
Vol 474 (8) ◽  
pp. 1395-1416 ◽  
Author(s):  
Cora Lilia Alvarez ◽  
Gerardo Corradi ◽  
Natalia Lauri ◽  
Irene Marginedas-Freixa ◽  
María Florencia Leal Denis ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Atpase Activity ◽  
Atp Release ◽  
Membrane Vesicles ◽  
Fold Increase ◽  
Extracellular Atp ◽  
Outer Membrane Vesicles ◽  
Dynamic Regulation ◽  
E Coli

We studied the kinetics of extracellular ATP (ATPe) in Escherichia coli and their outer membrane vesicles (OMVs) stimulated with amphipatic peptides melittin (MEL) and mastoparan 7 (MST7). Real-time luminometry was used to measure ATPe kinetics, ATP release, and ATPase activity. The latter was also determined by following [32P]Pi released from [γ-32P]ATP. E. coli was studied alone, co-incubated with Caco-2 cells, or in rat jejunum segments. In E. coli, the addition of [γ-32P]ATP led to the uptake and subsequent hydrolysis of ATPe. Exposure to peptides caused an acute 3-fold (MST7) and 7-fold (MEL) increase in [ATPe]. In OMVs, ATPase activity increased linearly with [ATPe] (0.1–1 µM). Exposure to MST7 and MEL enhanced ATP release by 3–7 fold, with similar kinetics to that of bacteria. In Caco-2 cells, the addition of ATP to the apical domain led to a steep [ATPe] increase to a maximum, with subsequent ATPase activity. The addition of bacterial suspensions led to a 6–7 fold increase in [ATPe], followed by an acute decrease. In perfused jejunum segments, exposure to E. coli increased luminal ATP 2 fold. ATPe regulation of E. coli depends on the balance between ATPase activity and ATP release. This balance can be altered by OMVs, which display their own capacity to regulate ATPe. E. coli can activate ATP release from Caco-2 cells and intestinal segments, a response which in vivo might lead to intestinal release of ATP from the gut lumen.

scholarly journals A Novel Gene Encoding Xanthan Lyase of Paenibacillus alginolyticus Strain XL-1

2000 ◽  
Vol 66 (9) ◽  
pp. 3945-3950 ◽  
Author(s):  
Harald J. Ruijssenaars ◽  
Sybe Hartmans ◽  
Jan C. Verdoes
Keyword(s):  
Signal Sequence ◽  
Fold Increase ◽  
Side Chain ◽  
Cloning And Sequencing ◽  
Gene Encoding ◽  
E Coli ◽  
Mature Enzyme ◽  
Locust Bean ◽  
Encoding Gene ◽  
Amino Acid Signal

ABSTRACT Xanthan-modifying enzymes are powerful tools in studying structure-function relationships of this polysaccharide. One of these modifying enzymes is xanthan lyase, which removes the terminal side chain residue of xanthan. In this paper, the cloning and sequencing of the first xanthan lyase-encoding gene is described, i.e., thexalA gene, encoding pyruvated mannose-specific xanthan lyase of Paenibacillus alginolyticus XL-1. ThexalA gene encoded a 100,823-Da protein, including a 36-amino-acid signal sequence. The 96,887-Da mature enzyme could be expressed functionally in Escherichia coli. Like the native enzyme, the recombinant enzyme showed no activity on depyruvated xanthan. Compared to production by P. alginolyticus, a 30-fold increase in volumetric productivity of soluble xanthan lyase was achieved by heterologous production in E. coli. The recombinant xanthan lyase was used to produce modified xanthan, which showed a dramatic loss of the capacity to form gels with locust bean gum.

scholarly journals Quinolone-resistant mutants of escherichia coli DNA topoisomerase IV parC gene.

1996 ◽  
Vol 40 (3) ◽  
pp. 710-714 ◽  
Author(s):  
Y Kumagai ◽  
J I Kato ◽  
K Hoshino ◽  
T Akasaka ◽  
K Sato ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Dna Gyrase ◽  
Mutant Gene ◽  
Missense Mutations ◽  
Topoisomerase Iv ◽  
Dna Topoisomerase ◽  
E Coli ◽  
A Subunit ◽  
Resistant Strains ◽  
Mutant Genes

Escherichia coli quinolone-resistant strains with mutations of the parC gene, which codes for a subunit of topoisomerase IV, were isolated from a quinolone-resistant gyrA mutant of DNA gyrase. Quinolone-resistant parC mutants were also identified among the quinolone-resistant clinical strains. The parC mutants became susceptible to quinolones by introduction of a parC+ plasmid. Introduction of the multicopy plasmids carrying the quinolone-resistant parC mutant gene resulted in an increase in MICs of quinolones for the parC+ and quinolone-resistant gyrA strain. Nucleotide sequences of the quinolone-resistant parC mutant genes were determined, and missense mutations at position Gly-78, Ser-80, or Glu-84, corresponding to those in the quinolone-resistance-determining region of DNA gyrase, were identified. These results indicate that topoisomerase IV is a target of quinolones in E. coli and suggest that the susceptibility of E. coli cells to quinolones is determined by sensitivity of the targets, DNA gyrase and topoisomerase IV.

scholarly journals EXPLORATION OF BROTH CHICKEN GUT AS GROWTH MEDIA OF Escherichia coli BL21 pET-Endo FOR ENDO-Β-1,4-D-XYLANASE PRODUCTION

2017 ◽  
Vol 13 (2) ◽  
pp. 191
Author(s):  
Anak Agung Istri Ratnadewi ◽  
Moch. Yoris Alidion ◽  
Agung Budi Santoso ◽  
Ika Oktavianawatia
Keyword(s):  
Large Scale ◽  
Incubation Temperature ◽  
Specific Activity ◽  
Hydrolytic Enzyme ◽  
Optimal Growth ◽  
Good Alternative ◽  
Growth Media ◽  
Gene Encoding ◽  
Xylanase Production ◽  
E Coli

<p>Endo-β-1,4-D-xylanase is a hydrolytic enzyme that breakdown the 1.4 chain of xylan polysaccharide. We have succes to transform the plasmid pET-Endo gene encoding endo-1,4-β-D-xylanase from Bacillus sp. originally from termites abdominal to E. coli BL21. The clone was ready for large scale of enzyme production. To reduce production cost, we look for subtitute media for the expensive Luria Berthani broth. Chicken guts broth is good alternative while rich of protein and very cheap. The content of N dissolved chicken guts broth reaches 87 % of LB broth. Growth of E. Coli BL21 in Chicken guts broth and LB broth (as control) was observed by Optical Density (OD) using spectrofotometer. Concentration of glucose added in broth and incubation temperature was varied. The result showed that optimal growth was in addition of 1.5 % glucose and incubated at  37 <sup>o</sup>C for 16 h. This optimal condition was used to grow E. coli BL21 pET-Endo for xylanase production. Enzyme purification was done by Ni-NTA affinity chromatography. Highest protein yield was 0.076 mg/mL obtained in 100 mM imidazole elucidation. The activity and specific activity of xylanase were estimated as 0.042 U/mL and 0.556 U/µg, respectively. The purification factor was 3.16 time and the molecular weight of enzyme was ± 30, 000 Dalton</p>

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