RESUMEN
A novel cellulose microfibril swelling (Cms) gene of Bacillus sp. AY8 was successfully cloned and sequenced using a set of primers designed based on the conserved region of the gene from the genomic database. The molecular cloning of the Cms gene revealed that the gene consisted of 679 bp sequences encoding 225 amino acids. Further in silico analysis unveiled that the Cms gene contained the NlpC/P60 conserved region that exhibited a homology of 98% with the NlpC/P60 family proteins found in both the strains, Burkholderialata sp. and Burkholderia vietnamiensis. The recombinant Cms enzyme had a significant impact on the reduction of crystallinity indices (CrI) of various substrates including a 3%, a 3.97%, a 4.66%, and a substantial 14.07% for filter paper, defatted cotton fiber, avicel, and alpha cellulose, respectively. Additionally, notable changes in the spectral features were observed among the substrates treated with recombinant Cms enzymes compared to the untreated control. Specifically, there was a decrease in band intensities within the spectral regions of 3000-3450 cm-1, 2900 cm-1, 1429 cm-1, and 1371 cm-1 for the treated filter paper, cotton fiber, avicel, and alpha cellulose, respectively. Furthermore, the recombinant Cms enzyme exhibited a maximum cellulose swelling activity at a pH of 7.0 along with a temperature of 40 °C. The molecular docking data revealed that ligand molecules, such as cellobiose, dextrin, maltose 1-phosphate, and feruloyated xyloglucan, effectively bonded to the active site of the Cms enzyme. The molecular dynamics simulations of the Cms enzyme displayed stable interactions with cellobiose and dextrin molecules up to 100 ns. It is noteworthy to mention that the conserved region of the Cms enzyme did not match with those of the bioadditives like expansins and swollenin proteins. This study is the initial report of a bacterial cellulose microfibril swellase enzyme, which could potentially serve as an additive to enhance biofuel production by releasing fermentable sugars from cellulose.
RESUMEN
Our previous study on the binding activity between Cel5H and clay minerals showed highest binding efficiency among other cellulase enzymes cloned. Here, based on previous studies, we hypothesized that the positive amino acids on the surface of Cel5H protein may play an important role in binding to clay surfaces. To examine this, protein sequences of Bacillus licheniformis Cel5H (BlCel5H) and Paenibacillus polymyxa Cel5A (PpCel5A) were analyzed and then selected amino acids were mutated. These mutated proteins were investigated for binding activity and force measurement via atomic force microscopy (AFM). A total of seven amino acids which are only present in BlCel5H but not in PpCel5A were selected for mutational studies and the positive residues which are present in both were omitted. Of the seven selected surface lysine residues, only three mutants K196A(M2), K54A(M3) and K157T(M4) showed 12%, 7% and 8% less clay mineral binding ability, respectively compared with wild-type. The probable reason why other mutants did not show altered binding efficiency might be due to relative location of amino acids on the protein surface. Meanwhile, measurement of adhesion forces on mica sheets showed a well-defined maximum at 69 ± 19 pN for wild-type, 58 ± 19 pN for M2, 53 ± 19 pN for M3, and 49 ± 19 pN for M4 proteins. Hence, our results demonstrated that relative location of surface amino acids of Cel5H protein especially positive charged amino acids are important in the process of clay mineral-protein binding interaction through electrostatic exchange of charges.
RESUMEN
The Cel genes from Bacillus licheniformis MSB03 were cloned and expressed to investigate binding ability on clay minerals and sea sand at pH ranging 3 to 9. FTIR analysis has been done to characterize bound enzymes on clay minerals. Subsequent, surveying of NCBI database for extracellular enzymes of soil bacteria was carried out. Among the five cloned Cel enzymes assayed for binding to clay minerals, only Cel5H enzyme had the binding ability. Enzyme Cel5H exhibited highest binding to montmorillonite followed by kaolinite and sea sand. Interestingly, Cel5H had higher pI value of 9.24 than other proteins (5.2-5.7). Cel5H binding to montmorillonite was shown to be negatively affected below pH 3 and above pH 9. Infrared absorption spectra of the Cel5H-montmorillonite complexes showed distinct peaks for clay minerals and bound proteins. Furthermore, database survey of soil bacterial extracellular enzymes revealed that Bacillus species enzymes had higher pI than other soil bacterial enzymes.
Asunto(s)
Bacillus licheniformis/enzimología , Celulasas/metabolismo , Arcilla , Bases de Datos de Proteínas , Punto Isoeléctrico , Minerales/metabolismo , Microbiología del Suelo , Celulasas/genética , Clonación Molecular , Hidrólisis , Unión Proteica , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismoRESUMEN
RcsA is a positive activator of extracellular polysaccharide (EPS) synthesis in the Enterobacteriaceae. The rcsA gene of the soft rot pathogen Pantoea sp. strain PPE7 in Pleurotus eryngii was cloned by PCR amplification, and its role in EPS synthesis and virulence was investigated. The RcsA protein contains 3 highly conserved domains, and the C-terminal end of the open reading frame shared significant amino acid homology to the helix-turn-helix DNA binding motif of bacterial activator proteins. The inactivation of rcsA by insertional mutagenesis created mutants that had decreased production of EPS compared to the wild-type strain and abolished the virulence of Pantoea sp. strain PPE7 in P. eryngii. The Pantoea sp. strain PPE7 rcsA gene was shown to strongly affect the formation of the disease symptoms of a mushroom pathogen and to act as the virulence factor to cause soft rot disease in P. eryngii.
RESUMEN
The study aimed to reveal the diversity of endophytic bacteria in the roots of Chinese cabbage (CC) cultivated in two areas in Korea, namely, Seosang-gun (SS) and Haenam-gun (HN), and also in a transgenic plant (TP) from the laboratory. A total of 653 colonies were isolated from the interior of CC roots, comprising 118, 302, and 233 isolates from SS, HN, and TP samples, respectively. Based on 16S rRNA gene sequence analysis, the isolates belonged to four major phylogenetic groups: high-G+C Gram-positive bacteria (HGC-GPB), low-G+C Gram-positive bacteria (LGC-GPB), Proteobacteria, and Bacteriodetes. The most dominant groups in the roots of the SS, HN, and TP cultivars were LGC-GPB (48.3%), Proteobacteria (50.2%), and HGC-GPB (38.2%), respectively. Importantly, most of the isolates that produced cell-walldegrading enzymes belonged to the genus Bacillus. Bacillus sp. (HNR03, TPR06), Bacillus pumilus (SSR07, HNR11, TPR07), and Bacillus subtilis (TPR03) showed high antagonism against the tested food-borne pathogenic bacteria. In addition, Bacillus sp. (HNR03, TPR06), Bacillus pumilus (SSR07, HNR11, HNR17, TPR11), Microbacterium oxidans (SSR09, TPR04), Bacillus cereus HNR10, Pseudomonas sp. HNR13, and Bacillus subtilis (TPR02, TPR03) showed strong antagonistic activity against the fungi Phythium ultimum, Phytophthora capsici, Fusarium oxysporum, and Rhizoctonia solani. The endophytes isolated from the TP cultivar showed the strongest antagonistic reactions against pathogens. This study is the first report on endophytic bacteria from Chinese cabbage roots.
Asunto(s)
Bacterias/clasificación , Bacterias/aislamiento & purificación , Brassica/microbiología , Antibiosis , Antifúngicos/farmacología , Bacterias/enzimología , Bacterias/genética , Biodiversidad , ADN Bacteriano/genética , Endófitos/clasificación , Endófitos/genética , Endófitos/aislamiento & purificación , Enfermedades de las Plantas/microbiología , Raíces de Plantas/microbiología , Plantas Modificadas Genéticamente/microbiología , República de Corea , Microbiología del SueloRESUMEN
BACKGROUND: Imperata cylindrica is being considered as a biomass candidate for bioethanol. This work aimed to evaluate a mild alkali pretreatment effect on the Imperata recalcitrant structure. Therefore, varied concentrations of NaOH (0, 7.5, 15, 20, and 25 g L(-1) ) were applied as treatments to Imperata at 105 °C for 10 min. RESULTS: Scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy studies revealed that 20 to 25 g L(-1) NaOH-treated Imperata exposed amorphous cellulose on surface granules composed of lignin, waxes, and partly hemicelluloses were abolished due to the comprehensive disruption of the linkages between lignin and carbohydrates. The cellulose crystalline index was increased with 7.5 to 20 g L(-1) NaOH treatments and reduced with a 25 g L(-1) NaOH treatment. In fact, the cellulose content in solids increased with the increasing NaOH concentration and was estimated to be 720 and 740 g kg(-1) for the 20 and 25 g L(-1) NaOH treatments, respectively. The yield of the reducing sugar was obtained 805 and 813 mg g(-1) from 20 and 25 g L(-1) NaOH-treated Imperata, respectively. CONCLUSION: Considering the cost of pretreatment, the 20 g L(-1) NaOH treatment is judged to be effective for disrupting Imperata recalcitrance in this pretreatment regime.
Asunto(s)
Biocombustibles/análisis , Etanol/química , Poaceae/citología , Biomasa , Pared Celular/efectos de los fármacos , Pared Celular/ultraestructura , Concentración de Iones de Hidrógeno , Hidrólisis , Hidróxido de Sodio/química , Temperatura , Factores de TiempoRESUMEN
A ß-1,3-1,4 glucanase gene of Paenibacillus sp. X4, bglc8H, was cloned and characterized. BGlc8H was predicted to be a protein of 409 amino acid residues, including a signal peptide of 31 amino acids. The mature enzyme was predicted to have 378 amino acid residues; its [corrected] molecular mass and pI were estimated as 41,561 Da and 7.61, respectively. BGlc8H belongs to glycoside hydrolase family 8 (GH8). Site-directed mutants of Glu95 and Asp156 of BGlc8H showed a near-complete loss of activity, indicating that they are catalytically-active residues. Unlike other GH8 members, BGlc8H had broad substrate specificity and hydrolyzed barley-ß-D-glucan > chitosan > carboxymethyl-cellulose > and lichenan. BGlc8H had a lower ratio of lichenase/barley-ß-D-glucanase activities compared to GH16 enzymes. BGlc8H was optimally active at pH 5 and 50 °C, except for barley-ß-D-glucanase (40 °C) and chitosanase (pH 7) activities. BGlc8H hydrolyzed cello-oligosaccharides (G3-G6) to G3 and G2 but not to G1. Ca(2+) increased the activity and thermostability of BGlc8H for lichenan suggesting its use for the saccharification of cellulosic biomass.
Asunto(s)
Glicósido Hidrolasas/metabolismo , Paenibacillus/enzimología , Especificidad por Sustrato , Secuencia de Aminoácidos , Sustitución de Aminoácidos , Clonación Molecular , Análisis por Conglomerados , Análisis Mutacional de ADN , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Ribosómico/química , ADN Ribosómico/genética , Estabilidad de Enzimas , Expresión Génica , Glicósido Hidrolasas/química , Glicósido Hidrolasas/genética , Glicósido Hidrolasas/aislamiento & purificación , Concentración de Iones de Hidrógeno , Punto Isoeléctrico , Datos de Secuencia Molecular , Peso Molecular , Mutagénesis Sitio-Dirigida , Paenibacillus/clasificación , Paenibacillus/genética , Paenibacillus/aislamiento & purificación , Filogenia , Mutación Puntual , Señales de Clasificación de Proteína , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , Homología de Secuencia de Aminoácido , Microbiología del Suelo , TemperaturaRESUMEN
Chlorpyrifos is an organophosphate pesticide that has adverse effect on animals and plants. We isolated endophytic bacterial strain, Pseudomonas sp. BF1-3, from balloon flower root which can hydrolyze chlorpyrifos. A gene (ophB) encoding a protein involved in chlorpyrifos degradation from this strain was cloned into Escherichia coli DH5α for confirming enzyme activity. After sequencing, total 1024bp nucleotide sequences were found in the open reading frame of ophB. The chlorpyrifos degradation patterns by E. coli DH5α (ophB) were observed. During incubation in minimal salt (M9) medium supplemented with chlorpyrifos (100mgL(-1)), the E. coli DH5α harboring ophB degraded about 97% initial chlorpyrifos (100mgL(-1)) and accumulated 86mgL(-1) 3,5,6-trichloro-2-pyridinol (TCP) within 9 days. In addition, optical density (OD) of E. coli DH5α (ophB) culture at 600nm was increased from 0.172 to 1.118 within 2 days of inoculation in the chlorpyrifos supplemented M9 medium. The estimated molecular weight of purified OphB protein was determined to be 31.4kDa by SDS-PAGE. The OphB enzyme was most active at pH 8 and an optimal temperature around 35°C. These results indicate that endophytic bacteria are supposed to be useful for biological control of environments contaminated with pesticides.
Asunto(s)
Arildialquilfosfatasa/genética , Cloropirifos/metabolismo , Insecticidas/metabolismo , Pseudomonas/genética , Secuencia de Aminoácidos , Arildialquilfosfatasa/aislamiento & purificación , Arildialquilfosfatasa/metabolismo , Secuencia de Bases , Biodegradación Ambiental , Endófitos/enzimología , Endófitos/genética , Escherichia coli/enzimología , Escherichia coli/crecimiento & desarrollo , Datos de Secuencia Molecular , Pseudomonas/enzimología , Piridonas/metabolismo , Proteínas Recombinantes/metabolismo , Análisis de Secuencia de ADNRESUMEN
The effect of dilute sodium hydroxide (NaOH) on reed straw structural change at 105 degreeC temperature was evaluated in this study. Various concentrations of NaOH (1% to 2.5%) were used for pretreatment of reed straw at 105 degreeC for 10min. Scanning electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy studies showed that 2% and 2.5% NaOH pretreated sample exposed more cellulose fibers compared with other treatments. The cellulose crystalline index was increased by the 1% to 2.0% NaOH treatments and slightly lowered by the 2.5% NaOH treatment due to destructing cellulose fibres. Two per cent NaOH pretreatment caused 69.9% lignin removal, whereas 2.5% NaOH pretreatment removed 72.4% lignin. Besides, reed straw, when pretreated at 2% and 2.5% NaOH, resulted 56.4% and 60.5% hemicellulose removal, respectively. However, the difference in removal of lignin and hemicellulose between 2% and 2.5% NaOH treated reed straw was very marginal. In addition, very negligible increase of cellulose level was estimated, amounting 78.8% and 76.6% in 2.5% and 2% NaOH-treated sample, respectively. Moreover, after 72 h, reducing sugar yield was 81.2% and 83.3% using enzyme loading of 15 FPU (g dry biomass)-' and 30 IU (g dry biomass)- and xylanase 4 FXU (g dry biomass)-1 from 2% and 2.5% NaOH pretreated reed straw, respectively. Reducing sugar yield was increased very marginally when NaOH concentration increased from 2% to 2.5% for reed straw pretreatment. Therefore, 2% NaOH is supposed to be effective for reed straw pretreatment at this mentioned condition.
Asunto(s)
Celulosa/química , Celulosa/ultraestructura , Componentes Aéreos de las Plantas/química , Componentes Aéreos de las Plantas/ultraestructura , Poaceae/química , Poaceae/ultraestructura , Hidróxido de Sodio/química , Álcalis/química , Concentración de Iones de Hidrógeno , Ensayo de MaterialesRESUMEN
Two cas genes were isolated from Pectobacterium carotovorum subsp. carotovorum LY34 (Pcc LY34). Sequence analysis of the 4873 bp cloned DNA fragment (accession number AY866383) revealed two open reading frames (casF and casB) that are predicted to encode 658 and 467 amino acid proteins, respectively. The CasF protein is similar to other PTS enzyme II components. casB encodes ß-glucosidase, a member of the glycosyl hydrolase family 1. An inverted repeat sequence was identified in the casB promoter region, and was hypothesized to have a negative effect on casB transcription. Replacement of the casB promoter of Pcc LY34 with the bglB promoter activated the casB gene, consistent with the repeats inhibiting expression of casB. Purified CasB enzyme was estimated to be 53,000 Da by SDS-PAGE, and hydrolyzed salicin, arbutin, pNPG, and MUG. CasB exhibited maximal activity toward pNPG at pH 7.0 and 40 °C, and Mg(2+) is essential for its activity. Two conserved glutamate residues (Glu(177) and Glu(366)) were shown to be important for CasB activity.
Asunto(s)
Pectobacterium carotovorum/enzimología , Pectobacterium carotovorum/genética , Activación Transcripcional , beta-Glucosidasa/genética , beta-Glucosidasa/metabolismo , ADN Bacteriano/química , ADN Bacteriano/genética , Estabilidad de Enzimas , Concentración de Iones de Hidrógeno , Secuencias Invertidas Repetidas , Ingeniería Metabólica , Datos de Secuencia Molecular , Peso Molecular , Sistemas de Lectura Abierta , Regiones Promotoras Genéticas , Recombinación Genética , Análisis de Secuencia de ADN , Especificidad por Sustrato , Temperatura , Transcripción Genética , beta-Glucosidasa/químicaRESUMEN
This work was conducted to evaluate the effect of dilute sodium hydroxide (NaOH) on barley straw at boiling temperature and fractionation of its biomass components into lignin, hemicellulose, and reducing sugars. To this end, various concentrations of NaOH (0.5% to 2%) were applied for pretreatment of barley straw at 105 degrees C for 10 min. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy studies revealed that 2% NaOHpretreated barley straw exposed cellulose fibers on which surface granules were abolished due to comprehensive removal of lignin and hemicellulose. The X-ray diffractometer (XRD) result showed that the crystalline index was increased with increased concentration of NaOH and found a maximum 71.5% for 2% NaOH-pretreated sample. The maximum removal of lignin and hemicellulose was 84.8% and 79.5% from 2% NaOH-pretreated liquor, respectively. Reducing sugar yield was 86.5% from 2% NaOH-pretreated sample using an enzyme dose containing 20 FPU of cellulase, 40 IU of beta-glucosidase, and 4 FXU of xylanase/g substrate. The results of this study suggest that it is possible to produce the bioethanol precursor from barley straw using 2% NaOH at boiling temperature.
Asunto(s)
Hordeum/efectos de los fármacos , Lignina/química , Lignina/ultraestructura , Hidróxido de Sodio/química , beta-Glucosidasa/metabolismo , Biocombustibles , Biomasa , Biotecnología/métodos , Hordeum/química , Hordeum/enzimología , Calor , Concentración de Iones de Hidrógeno , Hidrólisis , Microscopía de Fuerza Atómica , Polisacáridos/química , Polisacáridos/ultraestructura , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
We evaluated the effect of dilute sodium hydroxide (NaOH) on wheat straw at boiling temperature for removing lignin and increasing the yield of reducing sugar. Various concentrations of NaOH (0.5% to 2%) were used for pretreating wheat straw at 105 °C for 10 min. Scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy studies revealed that the 2% NaOH-pretreated sample exposed more cellulose fiber. The maximum respective removal of lignin and hemicellulose was 70.3% and 68.2% from the 2% NaOH-pretreated liquor. The reducing sugar yield was 84.6% using an enzyme dose containing 20 FPU of cellulase, 40 IU of ß-glucosidase and 4 FXU of xylanase/g of substrate. However, 2% NaOH-treated wheat straw had the lowest crystalline index of 52.5%, due to destructured cellulose fibers. The results indicate the effectiveness of producing the bioethanol precursor from wheat straw by using 2% NaOH at boiling temperature.
Asunto(s)
Biocombustibles , Etanol/metabolismo , Hidróxido de Sodio/farmacología , Temperatura de Transición , Triticum/efectos de los fármacos , Triticum/metabolismo , Celulosa/metabolismo , Etanol/química , Hidrólisis/efectos de los fármacos , Cinética , Lignina/metabolismo , Polisacáridos/metabolismo , Triticum/química , Triticum/enzimologíaRESUMEN
This study was conducted to assess the gene duplication and diversification of tandem cellulase genes in thermophilic bacteria. The tandem cellulase genes cel5C and cel5D were cloned from Thermotoga maritima MSB8, and a survey of the thermophilic bacterial genome for tandem cel genes from the databases was carried out. A clone having 2.3 kb fragment from T. maritima MSB8 showed cellulase activity, which had two open reading frames in tandem (cel5C and cel5D). The cel5C gene has 954 bp, which encodes a protein of 317 amino acid residues with a signal peptide of 23 amino acids, and the other gene cel5D consisting of 990 bp encoding a protein of 329 amino acid residues. These two proteins have similarity with the enzymes of glycosyl hydrolase family 5. From the enzyme assay, it was observed that Cel5C was extracellular and Cel5D was intracellular cellulase. Phylogenetic and homology matrix analyses of DNA and protein sequences revealed that family 12 cellulase enzymes Cel12A and Cel12B displayed higher homology (>50 %), but Cel5C and Cel5D enzymes belong to family 5 displayed lower homology (<30 %). In addition, repeated and mirror sequences in tandem genes are supposed to show the existence of gene duplication and recombination.
Asunto(s)
Celulasas/genética , Duplicación de Gen , Recombinación Genética , Thermotoga maritima/enzimología , Thermotoga maritima/genética , Celulasas/química , Clonación Molecular , ADN Bacteriano/genética , Evolución Molecular , Espacio Extracelular/enzimología , Glicósido Hidrolasas/genética , Espacio Intracelular/enzimología , Modelos Moleculares , Filogenia , Conformación Proteica , Thermotoga maritima/citologíaRESUMEN
XynX of Thermoanaerobacterium sp. [corrected] is a large, multimodular xylanase of 116 kDa. An Escherichia coli transformant carrying the entire xynX produced three active truncated xylanase species of 105, 85, and 64 kDa intracellularly. The Bacillus subtilis WB700 transformant with the xynX, a strain deficient in seven proteases including Vpr, secreted two active truncated xylanase species of 65 and 44 kDa. The B. subtilis WB800 transformant with xynX, a strain deficient in eight proteases including Vpr and WprA, secreted more active enzymes, 8.46 U ml(-1), mostly in the form of 105 and 85 kDa, than the WB700 transformant, 6.93 U ml(-1). This indicates that the additional deletion of wprA enabled the WB800 to secrete XynX in its intact form. B. subtilis WB800 produced more total enzyme activity than E. coli (1,692 ± 274 U vs. 141.9 ± 27.1 U), and, more importantly, secreted almost all the enzyme activity. The results suggest the potential use of B. subtilis WB800 as a host system for the production of large multimodular proteins.
Asunto(s)
Bacillus subtilis/enzimología , Bacillus subtilis/genética , Clostridium thermocellum/enzimología , Endo-1,4-beta Xilanasas/biosíntesis , Ingeniería Genética/métodos , Péptido Hidrolasas/deficiencia , Clostridium thermocellum/genética , Endo-1,4-beta Xilanasas/genética , Endo-1,4-beta Xilanasas/aislamiento & purificación , Escherichia coli/genéticaRESUMEN
The gene encoding an esterase enzyme was cloned from a metagenomic library of cow rumen bacteria. The esterase gene (est5S) was 1,026 bp in length, encoding a protein of 366 amino acid residues with a calculated molecular mass of 40,168 Da. The molecular mass of the enzyme was estimated to be 40,000 Da. The Est5S protein contains the Gly-X-Ser-X-Gly motif found in most bacterial and eukaryotic serine hydrolases. However, the Asp or Glu necessary for the catalytic triad [Ser-Asp-(Glu)-His] was not present, indicating Est5S represents a novel member of the GHSQG family of esterolytic enzymes. BlastP in the NCBI database analysis of Est5S revealed homology to hypothetical proteins and it had no homology to previous known lipases and esterases. Est5S was optimally active at pH 7.0 and 40 degrees C. Among the p-nitrophenyl acylesters tested, high enzymatic activities were observed on the short-chain p-nitrophenyl acylesters, such as p-nitrophenyl acetate, etc. The conserved serine residue (Ser190) was shown to be important for Est5S activity. The primers that amplified the est5S gene did not show any relative band with 49 species of culturable rumen bacteria. This implies that a new group esterase gene, est5S, may have come from a noncultured cow rumen bacterium.
Asunto(s)
Bacterias/enzimología , Esterasas/genética , Esterasas/metabolismo , Rumen/microbiología , Animales , Proteínas Bacterianas/genética , Proteínas Bacterianas/aislamiento & purificación , Proteínas Bacterianas/metabolismo , Bovinos , Clonación Molecular , ADN Bacteriano/química , ADN Bacteriano/genética , Estabilidad de Enzimas , Esterasas/química , Esterasas/aislamiento & purificación , Concentración de Iones de Hidrógeno , Cinética , Datos de Secuencia Molecular , Peso Molecular , Análisis de Secuencia de ADN , Homología de Secuencia de Aminoácido , Especificidad por Sustrato , TemperaturaRESUMEN
ß-Glucosidases are widespread in bacteria and involved in the metabolism of various carbohydrate substrates. Studying of ß-glucoside utilization (bgl) operons on operon of Pectobacterium carotovorum subsp. carotovorum LY34 (Pcc LY34) will help us understanding how ß-glucoside utilization (bgl) operon can cooperate with other systems in bacterium caused soft-rot disease. Pcc LY34 causes soft-rot disease in plants and expresses multiple enzymatic forms of ß-glucosidases. To fully explore the ß-glucoside utilization system in Pcc LY34, we have isolated a bgl operon from a genomic library for screening of ß-glucosidase activities. Sequence analysis of a 3050bp cloned DNA fragment (accession number AY870655) shows two open reading frames (bglY and bglK) that are predicted to encode proteins of 474 and 278 amino acid residues, respectively. Pair wise similarity analysis suggests BglY is a beta-glucosidase (a member of glycosyl hydrolase family 1) and BglK is a transcriptional antiterminator protein. bglY promoter region contains an inverted repeat sequence similar to transcriptional terminator. Different from other four ß-glucoside utilization operons of Pcc LY34 strain, BglY contains signal peptide sequences as extracellular ß-glucosidase. Comparisons of five ß-glucoside utilization operons of Pcc LY34 strain showed that bglYK operon does not have phosphotransferase system domain which are responsible for sugar transportation. BglY shares 33-44% identity with other four ß-glucosidases of Pcc LY34 strain. Enzyme assay showed that purified BglY enzyme hydrolyzed salicin, arbutin, pNPG, and MUG, and exhibited maximal activity at pH 7.0 and 40°C. This activity was enhanced Mg(2+). Site-directed mutagenesis revealed E166 and E371 are critical of BglY's ß-glucosidase activity.
Asunto(s)
Glucósidos/metabolismo , Redes y Vías Metabólicas/genética , Operón , Pectobacterium carotovorum/genética , Pectobacterium carotovorum/metabolismo , Secuencia de Aminoácidos , Secuencia de Bases , Clonación Molecular , ADN Bacteriano/química , ADN Bacteriano/genética , Datos de Secuencia Molecular , Sistemas de Lectura Abierta , Enfermedades de las Plantas/microbiología , Análisis de Secuencia de ADN , Homología de Secuencia de AminoácidoRESUMEN
A gene encoding an extracellular xylanase was cloned from a compost metagenomic library. The xylanase gene, xyn10J, was 1,137 bp in length and was predicted to encode a protein of 378 amino acid residues with a putative signal peptide of 27 amino acid residues. The molecular mass of the mature Xyn10J was calculated to be 39,882 Da with a pI of 6.09. Xyn10J had a motif GVKVHFTEMDI characteristic of most members of glycosyl hydrolase family 10. The amino acid sequence of Xyn10J showed 60.0% identity to that of XynH, a xylanase from an uncultured soil bacterium and 55% identity to XylC of Cellvibrio mixtus. Site-directed mutagenesis of the expected active site based on the sequence analysis indicated that an aspartic acid residue (Asp207), in addition to the identified catalytic residues Glu165 and Glu270, plays a crucial role for the catalytic activity. The purified Xyn10J had a mass of about 40 kDa and was optimally active at pH 7.0 and 40 °C. Xyn10J hydrolyzed beechwood xylan > birchwood xylan > oat spelt xylan > arabinoxylan. Xyn10J hydrolyzed xylotetraose and xylohexaose exclusively to xylobiose, xylopentaose, and xylotriose mainly to xylobiose with transglycosylation activity. The saccharification of reed (Phragmites communis) powder by commercial enzymes was significantly increased by the addition of a small amount of Xyn10J to the commercial preparation. Xyn10J is the first xylanase screened directly from a compost metagenomic library, and the enzyme has the potential to be used in the conversion of biomass to fermentable sugars for biofuel production.
Asunto(s)
Endo-1,4-beta Xilanasas/genética , Endo-1,4-beta Xilanasas/metabolismo , Biblioteca de Genes , Metagenómica , Microbiología del Suelo , Secuencia de Aminoácidos , Biomasa , Celulosa/metabolismo , Clonación Molecular , Endo-1,4-beta Xilanasas/química , Endo-1,4-beta Xilanasas/aislamiento & purificación , Evolución Molecular , Fermentación , Glicosilación , Datos de Secuencia Molecular , FilogeniaRESUMEN
A chitinolytic bacterium, designated strain SK16(T), was isolated from a mud flat in Suncheon Bay, Republic of Korea. Strain SK16(T) is Gram-negative, strictly aerobic, motile by a polar flagellum, and short rod-shaped. Phylogenetic analyses based on 16S rRNA gene sequences showed that the strain belonged to the genus Chitinibacter and was most closely related to Chitinibacter tainanensis S1(T) (98.2% similarity). DNA-DNA hybridization analyses showed a low association value of 20.45±4.08% between them. The major cellular fatty acids, the G+C content of the genomic DNA, and the predominant quinone of the strain were summed feature 3 (iso-C(15:0) 2-OH and/or C(16:1) ω7c; 50.5%) and C(12:0) (12.5%), 52.26 mol%, and Q-8, respectively. Based on the phylogenetic, chemotaxonomic, and phenotypic properties, strain SK16(T) represents a novel species of the genus Chitinibacter, for which the name Chitinibacter suncheonensis sp. nov. is proposed. The type strain is SK16(T) (=KCTC 23839(T) =DSM 25421(T)).
Asunto(s)
Neisseriaceae/clasificación , Neisseriaceae/genética , Microbiología del Suelo , Ácidos Grasos/química , Datos de Secuencia Molecular , Neisseriaceae/química , Neisseriaceae/aislamiento & purificación , Fenotipo , Filogenia , ARN Ribosómico 16S , República de CoreaRESUMEN
An experiment was done to determine the efficacy of waste bottom ash as an effective microbial carrier. Bottom ash found to be a suitable microbial carrier. The average of viable cells of Paenibacillus polymyxa GS01 (as a test biocontrol agent) in bottom ash samples was about 10(8) cfu/10 ± 2 mg. The surface of bottom ash coated with 5% PVA w/v was most effective for improvement of cell viability. TSB medium containing 50 mg/L of MnSO(4) · H(2)O was the best for spore production of P. polymyxa GS01. Thus waste bottom ash coating with 5% PVA is likely to be suitable for use as a microbial carrier.