Altering the Substrate Specificity of Organophosphorus Hydrolase for Enhanced Hydrolysis of Chlorpyrifos

ABSTRACT Chlorpyrifos is one of the most popular pesticides used for agriculture crop protection, and widespread contamination is a potential concern. However, chlorpyrifos is hydrolyzed almost 1,000-fold slower than the preferred substrate, paraoxon, by organophosphorus hydrolase (OPH), an enzyme that can degrade a broad range of organophosphate pesticides. We have recently demonstrated that directed evolution can be used to generate OPH variants with up to 25-fold improvement in hydrolysis of methyl parathion. The obvious question and challenge are whether similar success could be achieved with this poorly hydrolyzed substrate, chlorpyrifos. For this study, five improved variants were selected from two rounds of directed evolution based on the formation of clear haloes on Luria-Bertani plates overlaid with chlorpyrifos. One variant, B3561, exhibited a 725-fold increase in the k cat/Km value for chlorpyrifos hydrolysis as well as enhanced hydrolysis rates for several other OP compounds tested. Considering that wild-type OPH hydrolyzes paraoxon at a rate close to the diffusion control limit, the 39-fold improvement in hydrolysis of paraoxon by B3561 suggests that this variant is one of the most efficient enzymes available to attack a wide spectrum of organophosphate nerve agents.

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Development of Improved Cellulase Variants for the Conversion of Spent Mushroom Substrate Supplemented with Wheat Straw by Directed Evolution

10.21203/rs.3.rs-763119/v1 ◽

2021 ◽

Author(s):

Valentina Mauriello ◽

Anna Pennacchio ◽

Irantzu Alegria Dallo ◽

Laura Garcia Saez ◽

Petri Ihalainen ◽

...

Keyword(s):

Directed Evolution ◽

Wheat Straw ◽

Recombinant Expression ◽

Scale Up ◽

Wild Type ◽

Spent Mushroom Substrate ◽

Glucose Yield ◽

Hydrolysis Of ◽

Selection Of

Abstract To improve the Spent mushroom substrate (SMS) saccharification, cloning, recombinant expression in Escherichia coli and characterization of two new GH5 family cellulases (Cel1 and Cel2) were performed. Based on enzymes properties, Cel2 was selected for the generation of 30,000 random mutants by directed evolution in order to develop improved biocatalysts. Error-prone Polymerase Chain Reaction was used for diversity generation in cel2 gene and the screening for activity of mutants allowed selection of 63 improved variants that were subjected to a scale up production. Among these, 13 clones exhibited two-fold higher activity than Cel2 and a higher thermoresistance after 72h. The performances of these mutants in the hydrolysis of pretreated SMS/ wheat straw (40/60) were compared to the wild type Cel2 in conjunction with a commercial enzymatic mixture (MetZyme® SUNO™ BOOSTER 144). All the mutants exhibited a glucose yield two-fold or four fold higher than wild-type Cel2 after 72h of incubation.

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Evolutionary dynamics of asexual hypermutators adapting to a novel environment

10.1101/2021.07.28.454222 ◽

2021 ◽

Author(s):

Wei-Chin Ho ◽

Megan G. Behringer ◽

Samuel F. Miller ◽

Jadon Gonzales ◽

Amber Nguyen ◽

...

Keyword(s):

Adaptive Evolution ◽

Evolutionary Biology ◽

Evolutionary Dynamics ◽

Fold Increase ◽

Luria Bertani ◽

Mutation Rates ◽

Wild Type ◽

Novel Environment ◽

Luria Bertani Broth ◽

Nucleotide Mutation

How microbes adapt to a novel environment is a central question in evolutionary biology. While adaptive evolution must be fueled by beneficial mutations, whether higher mutation rates facilitate the rate of adaptive evolution remains unclear. To address this question, we cultured Escherichia coli hypermutating populations, in which a defective methyl-directed mismatch repair pathway causes a 140-fold increase in single-nucleotide mutation rates. In parallel with wild-type E. coli, populations were cultured in tubes containing Luria-Bertani broth, a complex medium known to promote the evolution of subpopulation structure. After 900 days of evolution, in three transfer schemes with different population-size bottlenecks, hypermutators always exhibited similar levels of improved fitness as controls. Fluctuation tests revealed that the mutation rates of hypermutator lines converged evolutionarily on those of wild-type populations, which may have contributed to the absence of fitness differences. Further genome-sequence analysis revealed that, although hypermutator populations have higher rates of genomic evolution, this largely reflects the effects of genetic draft under strong linkage. Despite these linkage effects, the evolved populations exhibit parallelism in fixed mutations, including those potentially related to biofilm formation, transcription regulation, and mutation-rate evolution. Together, these results generally negate the presumed relationship between high mutation rates and high adaptive speed of evolution, providing insight into how clonal adaptation occurs in novel environments.

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Directed Evolution and Structural Analysis of Alkaline Pectate Lyase from the Alkaliphilic Bacterium Bacillus sp. Strain N16-5 To Improve Its Thermostability for Efficient Ramie Degumming

Applied and Environmental Microbiology ◽

10.1128/aem.01017-15 ◽

2015 ◽

Vol 81 (17) ◽

pp. 5714-5723 ◽

Cited By ~ 27

Author(s):

Cheng Zhou ◽

Jintong Ye ◽

Yanfen Xue ◽

Yanhe Ma

Keyword(s):

Directed Evolution ◽

Textile Industry ◽

Specific Activity ◽

High Specific Activity ◽

Pectate Lyase ◽

Fold Increase ◽

Site Directed Mutagenesis ◽

Wild Type ◽

Content Type ◽

Alkaline Pectate Lyase

ABSTRACTThermostable alkaline pectate lyases have potential applications in the textile industry as an alternative to chemical-based ramie degumming processes. In particular, the alkaline pectate lyase fromBacillussp. strain N16-5 (BspPelA) has potential for enzymatic ramie degumming because of its high specific activity under extremely alkaline conditions without the requirement for additional Ca2+. However, BspPelA displays poor thermostability and is inactive after incubation at 50°C for only 30 min. Here, directed evolution was used to improve the thermostability of BspPelA for efficient and stable degumming. After two rounds of error-prone PCR and screening of >12,000 mutants, 10 mutants with improved thermostability were obtained. Sequence analysis and site-directed mutagenesis revealed that single E124I, T178A, and S271G substitutions were responsible for improving thermostability. Structural and molecular dynamic simulation analysis indicated that the formation of a hydrophobic cluster and new H-bond networks was the key factor contributing to the improvement in thermostability with these three substitutions. The most thermostable combined mutant, EAET, exhibited a 140-fold increase in thet50(time at which the enzyme loses 50% of its initial activity) value at 50°C, accompanied by an 84.3% decrease in activity compared with that of wild-type BspPelA, while the most advantageous combined mutant, EA, exhibited a 24-fold increase in thet50value at 50°C, with a 23.3% increase in activity. Ramie degumming with the EA mutant was more efficient than that with wild-type BspPelA. Collectively, our results suggest that the EA mutant, exhibiting remarkable improvements in thermostability and activity, has the potential for applications in ramie degumming in the textile industry.

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Functional expression of a yeast mitochondrial intron-encoded protein requires RNA processing at a conserved dodecamer sequence at the 3' end of the gene.

Molecular and Cellular Biology ◽

10.1128/mcb.9.4.1507 ◽

1989 ◽

Vol 9 (4) ◽

pp. 1507-1512 ◽

Cited By ~ 22

Author(s):

H Zhu ◽

H Conrad-Webb ◽

X S Liao ◽

P S Perlman ◽

R A Butow

Keyword(s):

Genetic Analysis ◽

Rna Processing ◽

Fold Increase ◽

Functional Expression ◽

Rrna Gene ◽

Yeast Mitochondria ◽

Wild Type ◽

Site Specific ◽

Var1 Gene ◽

A Site

All mRNAs of yeast mitochondria are processed at their 3' ends within a conserved dodecamer sequence, 5'-AAUAAUAUUCUU-3'. A dominant nuclear suppressor, SUV3-I, was previously isolated because it suppresses a dodecamer deletion at the 3' end of the var1 gene. We have tested the effects of SUV3-1 on a mutant containing two adjacent transversions within a dodecamer at the 3' end of fit1, a gene located within the 1,143-base-pair intron of the 21S rRNA gene, whose product is a site-specific endonuclease required in crosses for the quantitative transmission of that intron to 21S alleles that lack it. The fit1 dodecamer mutations blocked both intron transmission and dodecamer cleavage, neither of which was suppressed by SUV3-1 when present in heterozygous or homozygous configurations. Unexpectedly, we found that SUV3-1 completely blocked cleavage of the wild-type fit1 dodecamer and, in SUV3-1 homozygous crosses, intron conversion. In addition, SUV3-1 resulted in at least a 40-fold increase in the amount of excised intron accumulated. Genetic analysis showed that these phenotypes resulted from the same mutation. We conclude that cleavage of a wild-type dodecamer sequence at the 3' end of the fit1 gene is essential for fit1 expression.

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The TonB system in Aeromonas hydrophila NJ-35 is essential for MacA2B2 efflux pump-mediated macrolide resistance

Veterinary Research ◽

10.1186/s13567-021-00934-w ◽

2021 ◽

Vol 52 (1) ◽

Author(s):

Yuhao Dong ◽

Qing Li ◽

Jinzhu Geng ◽

Qing Cao ◽

Dan Zhao ◽

...

Keyword(s):

Aeromonas Hydrophila ◽

Efflux Pump ◽

Fold Increase ◽

Activity Level ◽

Macrolide Resistance ◽

Wild Type ◽

Iron Deprivation ◽

Pump Activity ◽

Tonb System ◽

Increased Sensitivity

AbstractThe TonB system is generally considered as an energy transporting device for the absorption of nutrients. Our recent study showed that deletion of this system caused a significantly increased sensitivity of Aeromonas hydrophila to the macrolides erythromycin and roxithromycin, but had no effect on other classes of antibiotics. In this study, we found the sensitivity of ΔtonB123 to all macrolides tested revealed a 8- to 16-fold increase compared with the wild-type (WT) strain, but this increase was not related with iron deprivation caused by tonB123 deletion. Further study demonstrated that the deletion of tonB123 did not damage the integrity of the bacterial membrane but did hinder the function of macrolide efflux. Compared with the WT strain, deletion of macA2B2, one of two ATP-binding cassette (ABC) types of the macrolide efflux pump, enhanced the sensitivity to the same levels as those of ΔtonB123. Interestingly, the deletion of macA2B2 in the ΔtonB123 mutant did not cause further increase in sensitivity to macrolide resistance, indicating that the macrolide resistance afforded by the MacA2B2 pump was completely abrogated by tonB123 deletion. In addition, macA2B2 expression was not altered in the ΔtonB123 mutant, indicating that any influence of TonB on MacA2B2-mediated macrolide resistance was at the pump activity level. In conclusion, inactivation of the TonB system significantly compromises the resistance of A. hydrophila to macrolides, and the mechanism of action is related to the function of MacA2B2-mediated macrolide efflux.

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Nonrecombinant meiosis I nondisjunction in Saccharomyces cerevisiae induced by tRNA ochre suppressors.

Genetics ◽

10.1093/genetics/123.1.81 ◽

1989 ◽

Vol 123 (1) ◽

pp. 81-95 ◽

Cited By ~ 1

Author(s):

E J Louis ◽

J E Haber

Keyword(s):

Saccharomyces Cerevisiae ◽

Mitotic Chromosome ◽

Stop Codon ◽

Fold Increase ◽

Wild Type ◽

Yeast Saccharomyces Cerevisiae ◽

Nonsense Mutations ◽

Chromosome Iii ◽

Meiosis I ◽

Chromosome Nondisjunction

Abstract The presence of the tRNA ochre suppressors SUP11 and SUP5 is found to induce meiosis I nondisjunction in the yeast Saccharomyces cerevisiae. The induction increases with increasing dosage of the suppressor and decreases in the presence of an antisuppressor. The effect is independent of the chromosomal location of SUP11. Each of five different chromosomes monitored exhibited nondisjunction at frequencies of 0.1%-1.1% of random spores, which is a 16-160-fold increase over wild-type levels. Increased nondisjunction is reflected by a marked increase in tetrads with two and zero viable spores. In the case of chromosome III, for which a 50-cM map interval was monitored, the resulting disomes are all in the parental nonrecombinant configuration. Recombination along chromosome III appears normal both in meioses that have no nondisjunction and in meioses for which there was nondisjunction of another chromosome. We propose that a proportion of one or more proteins involved in chromosome pairing, recombination or segregation are aberrant due to translational read-through of the normal ochre stop codon. Hygromycin B, an antibiotic that can suppress nonsense mutations via translational read-through, also induces nonrecombinant meiosis I nondisjunction. Increases in mistranslation, therefore, increase the production of aneuploids during meiosis. There was no observable effect of SUP11 on mitotic chromosome nondisjunction; however some disomes caused SUP11 ade2-ochre strains to appear white or red, instead of pink.

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Phosphoglycolate has profound metabolic effects but most likely no role in a metabolic DNA response in cancer cell lines

Biochemical Journal ◽

10.1042/bcj20180435 ◽

2019 ◽

Vol 476 (4) ◽

pp. 629-643 ◽

Cited By ~ 1

Author(s):

Isabelle Gerin ◽

Marina Bury ◽

Francesca Baldin ◽

Julie Graff ◽

Emile Van Schaftingen ◽

...

Keyword(s):

Dna Damage ◽

Cell Lines ◽

Oxidative Dna Damage ◽

Fold Increase ◽

Metabolic Effects ◽

Phosphoglycerate Mutase ◽

Wild Type ◽

Metabolic Disturbances ◽

Phosphoglycolate Phosphatase ◽

Damage Repair

Abstract Repair of a certain type of oxidative DNA damage leads to the release of phosphoglycolate, which is an inhibitor of triose phosphate isomerase and is predicted to indirectly inhibit phosphoglycerate mutase activity. Thus, we hypothesized that phosphoglycolate might play a role in a metabolic DNA damage response. Here, we determined how phosphoglycolate is formed in cells, elucidated its effects on cellular metabolism and tested whether DNA damage repair might release sufficient phosphoglycolate to provoke metabolic effects. Phosphoglycolate concentrations were below 5 µM in wild-type U2OS and HCT116 cells and remained unchanged when we inactivated phosphoglycolate phosphatase (PGP), the enzyme that is believed to dephosphorylate phosphoglycolate. Treatment of PGP knockout cell lines with glycolate caused an up to 500-fold increase in phosphoglycolate concentrations, which resulted largely from a side activity of pyruvate kinase. This increase was much higher than in glycolate-treated wild-type cells and was accompanied by metabolite changes consistent with an inhibition of phosphoglycerate mutase, most likely due to the removal of the priming phosphorylation of this enzyme. Surprisingly, we found that phosphoglycolate also inhibits succinate dehydrogenase with a Ki value of <10 µM. Thus, phosphoglycolate can lead to profound metabolic disturbances. In contrast, phosphoglycolate concentrations were not significantly changed when we treated PGP knockout cells with Bleomycin or ionizing radiation, which are known to lead to the release of phosphoglycolate by causing DNA damage. Thus, phosphoglycolate concentrations due to DNA damage are too low to cause major metabolic changes in HCT116 and U2OS cells.

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degS Is Necessary for Virulence and Is among Extraintestinal Escherichia coli Genes Induced in Murine Peritonitis

Infection and Immunity ◽

10.1128/iai.71.6.3088-3096.2003 ◽

2003 ◽

Vol 71 (6) ◽

pp. 3088-3096 ◽

Cited By ~ 40

Author(s):

Peter Redford ◽

Paula L. Roesch ◽

Rodney A. Welch

Keyword(s):

Escherichia Coli ◽

Urinary Tract Infection ◽

Urinary Tract ◽

Tract Infection ◽

Luria Bertani ◽

Broth Culture ◽

Wild Type ◽

E Coli ◽

Virulence Attenuation

ABSTRACT Extraintestinal Escherichia coli strains cause meningitis, sepsis, urinary tract infection, and other infections outside the bowel. We examined here extraintestinal E. coli strain CFT073 by differential fluorescence induction. Pools of CFT073 clones carrying a CFT073 genomic fragment library in a promoterless gfp vector were inoculated intraperitoneally into mice; bacteria were recovered by lavage 6 h later and then subjected to fluorescence-activated cell sorting. Eleven promoters were found to be active in the mouse but not in Luria-Bertani (LB) broth culture. Three are linked to genes for enterobactin, aerobactin, and yersiniabactin. Three others are linked to the metabolic genes metA, gltB, and sucA, and another was linked to iha, a possible adhesin. Three lie before open reading frames of unknown function. One promoter is associated with degS, an inner membrane protease. Mutants of the in vivo-induced loci were tested in competition with the wild type in mouse peritonitis. Of the mutants tested, only CFT073 degS was found to be attenuated in peritoneal and in urinary tract infection, with virulence restored by complementation. CFT073 degS shows growth similar to that of the wild type at 37°C but is impaired at 43°C or in 3% ethanol LB broth at 37°C. Compared to the wild type, the mutant shows similar serum survival, motility, hemolysis, erythrocyte agglutination, and tolerance to oxidative stress. It also has the same lipopolysaccharide appearance on a silver-stained gel. The basis for the virulence attenuation is unclear, but because DegS is needed for σE activity, our findings implicate σE and its regulon in E. coli extraintestinal pathogenesis.

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Enhancement of the Efficiency of Secretion of Heterologous Lipase in Escherichia coli by Directed Evolution of the ABC Transporter System

Applied and Environmental Microbiology ◽

10.1128/aem.71.7.3468-3474.2005 ◽

2005 ◽

Vol 71 (7) ◽

pp. 3468-3474 ◽

Cited By ~ 19

Author(s):

Gyeong Tae Eom ◽

Jae Kwang Song ◽

Jung Hoon Ahn ◽

Yeon Soo Seo ◽

Joon Shick Rhee

Keyword(s):

Escherichia Coli ◽

Directed Evolution ◽

Abc Transporter ◽

Microtiter Plate ◽

Single Amino Acid ◽

Wild Type ◽

E Coli ◽

Single Amino Acid Change ◽

Secretion Efficiency

ABSTRACT The ABC transporter (TliDEF) from Pseudomonas fluorescens SIK W1, which mediated the secretion of a thermostable lipase (TliA) into the extracellular space in Escherichia coli, was engineered using directed evolution (error-prone PCR) to improve its secretion efficiency. TliD mutants with increased secretion efficiency were identified by coexpressing the mutated tliD library with the wild-type tliA lipase in E. coli and by screening the library with a tributyrin-emulsified indicator plate assay and a microtiter plate-based assay. Four selected mutants from one round of error-prone PCR mutagenesis, T6, T8, T24, and T35, showed 3.2-, 2.6-, 2.9-, and 3.0-fold increases in the level of secretion of TliA lipase, respectively, but had almost the same level of expression of TliD in the membrane as the strain with the wild-type TliDEF transporter. These results indicated that the improved secretion of TliA lipase was mediated by the transporter mutations. Each mutant had a single amino acid change in the predicted cytoplasmic regions in the membrane domain of TliD, implying that the corresponding region of TliD was important for the improved and successful secretion of the target protein. We therefore concluded that the efficiency of secretion of a heterologous protein in E. coli can be enhanced by in vitro engineering of the ABC transporter.

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Engineering Desiccation Tolerance inEscherichia coli

Applied and Environmental Microbiology ◽

10.1128/aem.66.4.1680-1684.2000 ◽

2000 ◽

Vol 66 (4) ◽

pp. 1680-1684 ◽

Cited By ~ 60

Author(s):

Daniela Billi ◽

Deborah J. Wright ◽

Richard F. Helm ◽

Todd Prickett ◽

Malcolm Potts ◽

...

Keyword(s):

Escherichia Coli ◽

Phase Transition ◽

Freeze Drying ◽

Fold Increase ◽

Inescherichia Coli ◽

Vibration Frequencies ◽

Wild Type ◽

Air Drying ◽

Phase Transition Temperatures ◽

Cell Dehydration

ABSTRACT Recombinant sucrose-6-phosphate synthase (SpsA) was synthesized inEscherichia coli BL21DE3 by using the spsA gene of the cyanobacterium Synechocystis sp. strain PCC 6803. Transformants exhibited a 10,000-fold increase in survival compared to wild-type cells following either freeze-drying, air drying, or desiccation over phosphorus pentoxide. The phase transition temperatures and vibration frequencies (PO stretch) in phospholipids suggested that sucrose maintained membrane fluidity during cell dehydration.

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