Chromobacterium Sp Research Articles

Chromobacterium biopesticide overcomes insecticide resistance in malaria vector mosquitoes.

Vector mosquito control is an integral part of malaria control. The global emergence of insecticide resistance in malaria-transmitting Anophelines has become an impediment and has created an urgent need for novel mosquito control approaches. Here, we show that a biopesticide derived from the soil-dwelling bacterium Chromobacterium sp. Panama (Csp_P) kills insecticide-resistant Anopheles mosquitoes, regardless of their resistance mechanisms. In addition, sublethal dose of Csp_P acts as a synergist to now used chemical insecticides across multiple classes. Moreover, Csp_P reduces host-seeking behavior and malaria parasite infection in vector mosquitoes in ways that further decrease transmission. Mosquito glutathione S-transferases are essential for Csp_P's mosquito-killing mechanism. Enclosed field trials in Burkina Faso, conducted in diverse ecological settings and supported by a mathematical model, have now demonstrated its potential for malaria control in settings with widespread insecticide resistance.

Halotolerant Bacteria from Genus Nesterenkonia sandarakina VSA9 as a Potential Polyhydroxyalkanoate Producer.

Nesterenkonia sandarakina VSA9 pigmented bacteria isolated from Sargassum is being reported to produce polyhydroxyalkanoates (PHA) deduced through detecting the presence of pha C gene using the molecular method. The PHA synthase gene was of type I which has been concluded from the phylogenetic tree and multiple sequence analysis. The amino acid analysis of pha C gene confirms the involvement of the lipase box having a sequence of G-Y-C-I-G-G with cysteine as the active center of the PHA synthase. Homology modeling predicted the 3D protein structure which is similar to the PHA synthase of Chromobacterium sp. USM2. The solvent extract of N. sandarakina VSA9 showed the presence of Carotenoid compound with maximum wavelength at 475nm. The study's findings could have far-reaching implications, contributing to advancements in the biotechnology, industrial processes, and sustainable practices. The simultaneous production of carotenoids and PHAs by N. sandarakina VSA9 presents exciting opportunities for the development of innovative and environmentally friendly applications.

Directed evolution of cholesterol oxidase with improved thermostability using error-prone PCR.

Cholesterol oxidase is industrially important as it is frequently used as a biosensor in food and agriculture industries and measurement of cholesterol. Although, most natural enzymes show low thermostability, which limits their application. Here, we obtained an improved variant of Chromobacterium sp. DS1 cholesterol oxidase (ChOS) with enhanced thermostability by random mutant library applying two forms of error-prone PCR (serial dilution and single step). Wild-type ChOS indicated an optimal temperature and pH of 70 ºC and pH 7.5, respectively. The best mutant ChOS-M acquired three amino acid substitutions (S112T, I240V and A500S) and enhanced thermostability (at 50°C for 5h) by 30%. The optimum temperature and pH in the mutant were not changed. In comparison to wild type, circular dichroism disclosed no significant secondary structural alterations in mutants. These findings show that error-prone PCR is an effective method for enhancing enzyme characteristics and offers a platform for the practical use of ChOS as a thermal-resistance enzyme in industrial fields and clinical diagnosis.

Characterization and Homology Modeling of Catalytically Active Recombinant PhaCAp Protein from Arthrospira platensis.

Polyhydroxybutyrate (PHB) is a biocompatible and biodegradable polymer that has the potential to replace fossil-derived polymers. The enzymes involved in the biosynthesis of PHB are β-ketothiolase (PhaA), acetoacetyl-CoA reductase (PhaB), and PHA synthase (PhaC). PhaC in Arthrospira platensis is the key enzyme for PHB production. In this study, the recombinant E. cloni®10G cells harboring A. platensis phaC (rPhaCAp) was constructed. The overexpressed and purified rPhaCAp with a predicted molecular mass of 69 kDa exhibited Vmax, Km, and kcat values of 24.5 ± 2 μmol/min/mg, 31.3 ± 2 µM and 412.7 ± 2 1/s, respectively. The catalytically active rPhaCAp was a homodimer. The three-dimensional structural model for the asymmetric PhaCAp homodimer was constructed based on Chromobacterium sp. USM2 PhaC (PhaCCs). The obtained model of PhaCAp revealed that the overall fold of one monomer was in the closed, catalytically inactive conformation whereas the other monomer was in the catalytically active, open conformation. In the active conformation, the catalytic triad residues (Cys151-Asp310-His339) were involved in the binding of substrate 3HB-CoA and the CAP domain of PhaCAp involved in the dimerization.

Extended Spectrum Beta-Lactamase Expressing <i>Chromobacterium</i> Sp. Dyh27s2016 Strain is Capable of Metal Leaching in Electronic Waste

Printed circuit boards (PCBs) contain many precious and hazardous metals, and the disposal of a large number of electronic wastes (e-waste) has been a serious environmental concern. The conventional metallurgy methods used to recover metals from e-wastes require higher energy expenditure besides contributing to significant environmental pollution. This necessitated an alternative approach, such as using cyanogenic and other environmental bacteria to recover metals from e-waste. Hence, the current study is aimed to explore the feasibility of Chromobacterium sp. Dyh27s2016 strain in mobilising metals from e-waste. A two-step bioleaching process was employed with the ATCC culture Chromobacteriumviolecium Bergonzini (12472TM) used as a control. The metal content in the supernatant was analysed using the inductively coupled plasma - optical emission spectrometry (ICP-OES) technique. Meanwhile, the metal concentration in PCBs was also assessed using the acid reflux method followed by the ICP-OES analysis. Besides, the Chromobacterium sp. Dyh27s2016 strain was also assessed for the beta-lactam antibiotics resistance and the gene expression for extended spectrum beta-lactamase (ESBL). It was observed that Chromobacterium sp. Dyh27s2016 strain mobilises 80, 94, 52 and 56% of Cu, Fe, Zn and Ag respectively from e-waste. However, this strain was found resistant to penicillin G sodium, ampicillin sodium and ticarcillin disodium but susceptible to cefotaxime sodium antibiotics. The molecular analysis showed that this strain possessed the ESBL genes, TEM and CTX-M. The findings from this study enable potential industrial applications for recycling electronic trash using Chromobacterium Dyh27s2016 strains in future.

Bacterial survey of skin ulcers in Anguilla anguilla L. females during artificial maturation under controlled conditions

Controlled indoor reproduction of European eel is commonly recognized as a prospective tool to prevent extinction of this fish species. There is a little information about diversity of bacterial microflora of European eel during long maturation under controlled but changing thermal and salinity conditions. Characteristics of the composition of the bacterial microflora inhabiting the body surface of fish kept firstly in fresh and then in salt water, may help enhance the survival of spawners and spawning efficiency. Knowledge about the presence of potentially pathogenic bacterial species and their antibiotic resistance is particularly important. Methods: This study analyzed the bacterial microflora of two types of necrotic changes on the skin of eel females during artificial maturation under fresh and saltwater conditions. Results: A total of two hundred and forty bacterial strains were isolated from necrotic dermal changes on fish in freshwater and saltwater conditions. Both the bacterial number and biodiversity were greater in freshwater than in saltwater. Psychrophilic bacterial strains in freshwater were twice as abundant as in saltwater, especially among isolates which were cultured from the mucus or from ulcerative changes around the chip injection point (up to 1010 cfu/mL). 16 S ribosomal RNA gene sequencing of isolates from the freshwater conditions revealed the presence of twenty genera of bacteria, including: Pseudomonas sp., Comamonas sp., Escherichia sp., Aeromonas sp., Citrobacter sp., Burkholderia sp., Pantoea sp., Enterobacter sp., Yersinia sp., Edwardsiella sp., Serratia sp., Bordetella sp., Morganella sp. and Chromobacterium sp. In saltwater conditions, five genera of bacteria were found dominantly: Pseudomonas sp., Aeromonas sp., Yersinia sp., Vibrio sp., Edwardsiella sp. In freshwater conditions, the bacteria were mostly resistant or resistant to all tested antimicrobial drugs. Conclusions: Changes in bacterial microflora during controlled indoor reproduction of European eel predispose fish to bacterial infection especially during the first freshwater step of female maturation. New, alternative to antibiotic therapy, methods should be adopted to prevent infections and enhance spawning efficiency.

Class I Polyhydroxyalkanoate (PHA) Synthase Increased Polylactic Acid Production in Engineered Escherichia Coli.

Polylactic acid (PLA), a homopolymer of lactic acid (LA), is a bio-derived, biocompatible, and biodegradable polyester. The evolved class II PHA synthase (PhaC1 Ps6-19) was commonly utilized in the de novo biosynthesis of PLA from biomass. This study tested alternative class I PHA synthase (PhaC Cs ) from Chromobacterium sp. USM2 in engineered Escherichia coli for the de novo biosynthesis of PLA from glucose. The results indicated that PhaC Cs had better performance in PLA production than that of class II synthase PhaC1 Ps6-19. In addition, the sulA gene was engineered in PLA-producing strains for morphological engineering. The morphologically engineered strains present increased PLA production. This study also tested fused propionyl-CoA transferase and lactate dehydrogenase A (fused Pct Cp /LdhA) in engineered E. coli and found that fused Pct Cp /LdhA did not apparently improve the PLA production. After systematic engineering, the highest PLA production was achieved by E. coli MS6 (with PhaC Cs and sulA), which could produce up to 955.0 mg/L of PLA in fed-batch fermentation with the cell dry weights of 2.23%, and the average molecular weight of produced PLA could reach 21,000 Da.

Expression and characterization of cholesterol oxidase with high thermal and pH stability from Janthinobacterium agaricidamnosum

Cholesterol oxidases (COXases) have a diverse array of applications including analysis of blood cholesterol levels, synthesis of steroids, and utilization as an insecticidal protein. The COXase gene from Janthinobacterium agaricidamnosum was cloned and expressed in Escherichia coli. The purified COXase showed an optimal temperature of 60 °C and maintained about 96 and 72% of its initial activity after 30 min at 60 and 70 °C, respectively. In addition, the purified COXase exhibited a pH optimum at 7.0 and high pH stability over the broad pH range of 3.0–12.0. The pH stability of the COXase at pH 12.0 was higher than that of highly stable COXase from Chromobacterium sp. DS-1. The COXase oxidized cholesterol and β-cholestanol at higher rates than other 3β-hydroxysteroids. The Km, Vmax, and kcat values for cholesterol were 156 μM, 13.7 μmol/min/mg protein, and 14.4 s−1, respectively. These results showed that this enzyme could be very useful in the clinical determination of cholesterol in serum and the production of steroidal compounds. This is the first report to characterize a COXase from the genus Janthinobacterium.

Polyhydroxyalkanoate synthase (PhaC): The key enzyme for biopolyester synthesis

• The structure of PHA synthase (PhaC) consists of an N-terminal domain and a C-terminal catalytic domain. • The N-terminal domain plays a role in many aspects including the formation and stability of the dimer, the enzymatic activity, the substrate specificity, the molecular weight of PHA produced, the expression of PhaC and its ability to bind to PHA granules and other PHA-related proteins. • The C-terminal catalytic domain consists of a cap subdomain, a substrate entrance channel, an active site, and a product egress tunnel. Polyhydroxyalkanoates (PHAs) are considered good candidates in replacing commercial petrochemical plastics in certain applications like single-use packaging since they are biodegradable, biocompatible and share similar properties with conventional plastics. PHA synthase (PhaC) is the key enzyme in PHA biosynthesis. There are four classes of PhaC, namely, class I, class II, class III and class IV, each with their distinct characteristics. To date, there are two PhaCs with successfully solved catalytic domain structures. They are PhaC from C. necator (PhaC Cn -CAT) (Ser201–Ala589) and PhaC from Chromobacterium sp. USM2 (PhaC C s -CAT) (Phe175–Asn567). Generally, the structure of PhaC consists of an N-terminal domain and a C-terminal catalytic domain. The N-terminal domain is flexible and has not been successfully visualized in any existing structures of PhaC. It is suggested to affect the dimerization and stability of the PhaC dimer, enzymatic activity, substrate specificity, molecular weight of PHA produced, expression of PhaC, and its ability to bind to PHA granules and PHA-related proteins. The C-terminal catalytic domain contains the cap subdomain, substrate entrance channel, active site, and product egress tunnel.

Biosynthesis of Poly(3HB-co-3HP) with Variable Monomer Composition in Recombinant Cupriavidus necator H16.

Polyhydroxyalkanoates are attractive alternatives to traditional plastics. However, although polyhydroxybutyrate (PHB) is produced in large quantities by Cupriavidus necator H16, its properties are far from ideal for the manufacture of plastic products. These properties may be improved through its coproduction with 3-hydroxypropionate (3HP), which leads to the formation of the copolymer poly(3-hydroxybutyrate-co-3-hydroxypropionate) (poly(3HB-co-3HP). To achieve this, a pathway was designed to enable C.necator H16 to convert β-alanine to 3HP. The initial low levels of incorporation of 3HP into the copolymer were overcome by the overproduction of the native propionyl-CoA transferase together with PHA synthase from Chromobacterium sp. USM2. Following optimization of 3HP incorporation into the copolymer, the molar fraction of 3HP could be controlled by cultivation in medium containing different concentrations of β-alanine. Between 0 and 80 mol % 3HP could be achieved. Further supplementation with 2 mM cysteine increased the maximum 3HP molar fraction to 89%. Additionally, the effect of deletions of the phaA and phaB1 genes of the phaCAB operon on 3HP molar fraction were investigated. A phaAB1 double knockout resulted in a copolymer containing 91 mol % 3HP without the need for cysteine supplementation.

Evaluation of Microbial Loads and Physico-Chemicals of Cassava Mill Effluent Simulated Soil

Evaluation of microbial loads and physico-chemicals of cassava mill effluent simulated soil was carried out using standard microbiological and biochemical techniques. This was to determine the effect of cassava mill effluent (CME) on rhizosphere microbial loads, physicochemical properties, nitrogenous salt and heavy metals. The results showed that CME effect on the physicochemical determinants (pH, Ca, Mg, K) and heavy metal determinant (Fe, Zn, Co, Ni, Pb and Mn) was concentration dependents. The nitrogenous salts (NO3, NH4+ and NO2) levels progressively increased with no significant differences (p>0.05 ANOVA). The microbial isolates were: Saccharomyces sp, Mucorindicus, Fusarium sp and Gliocladium sp for the fungal group. The bacterial group were Chromobacterium sp, Corynebacterium sp, Bacillus sp, Acinetobacter sp and Escherichia coli while the nitrogen-fixing bacterial group were Azotobacter sp., Azospirillum sp., Frankia sp., Bradyrhizobium sp., Hebaspirillum sp., Cyanobacteria (or blue green algae), Anabaena sp, Nostoc sp., Clostridium sp. and Rhizobium sp. There was no significant differences (p>0.05) in the rhizosphere microbial load across the concentration gradient at the CME-simulated plot phyto-remediated by Centrosema pubesscens and Calopogonium mucunoides. Agricultural wastes such as cassava mill effluent should be properly treated before discharging to the environment in other to prevent the loss of nitrogen-fixing bacteria and total heterotrophic bacterial genera that could be of immense importance to man.

Display of Microbial Glucose Dehydrogenase and Cholesterol Oxidase on the Yeast Cell Surface for the Detection of Blood Biochemical Parameters.

High levels of blood glucose are always associated with numerous complications including cholesterol abnormalities. Therefore, it is important to simultaneously monitor blood glucose and cholesterol levels in patients with diabetes during the management of chronic diseases. In this study, a glucose dehydrogenase from Aspergillus oryzae TI and a cholesterol oxidase from Chromobacterium sp. DS-1 were displayed on the surface of Saccharomyces cerevisiae, respectively, using the yeast surface display system at a high copy number. In addition, two whole-cell biosensors were constructed through the immobilization of the above yeast cells on electrodes, for electrochemical detection of glucose and cholesterol. The assay time was 8.5 s for the glucose biosensors and 30 s for the cholesterol biosensors. Under optimal conditions, the cholesterol biosensor exhibited a linear range from 2 to 6 mmol·L−1. The glucose biosensor responded efficiently to the presence of glucose at a concentration range of 20–600 mg·dL−1 (1.4–33.3 mmol·L−1) and showed excellent anti-xylose interference properties. Both biosensors exhibited good performance at room temperature and remained stable over a three-week storage period.

Asymmetric Open-Closed Dimer Mechanism of Polyhydroxyalkanoate Synthase PhaC.

SummaryBiodegradable polyester polyhydroxyalkanoate (PHA) is a promising bioplastic material for industrial use as a replacement for petroleum-based plastics. PHA synthase PhaC forms an active dimer to polymerize acyl moieties from the substrate acyl-coenzyme A (CoA) into PHA polymers. Here we present the crystal structure of the catalytic domain of PhaC from Chromobacterium sp. USM2, bound to CoA. The structure reveals an asymmetric dimer, in which one protomer adopts an open conformation bound to CoA, whereas the other adopts a closed conformation in a CoA-free form. The open conformation is stabilized by the asymmetric dimerization and enables PhaC to accommodate CoA and also to create the product egress path. The bound CoA molecule has its β-mercaptoethanolamine moiety extended into the active site with the terminal SH group close to active center Cys291, enabling formation of the reaction intermediate by acylation of Cys291.

Bakteri Agens Hayati Potensial terhadap Patogen Penting pada Padi

Saat ini teknologi pengendalian hayati penyakit utama padi terus berkembang. Dalam pengembangan teknologi pengendalian hayati, mekanisme penghambatan patogen dalam perkembangan penyakit pada suatu populasi tumbuhan dalam area tertentu menjadi hal yang penting. Penelitian bertujuan mendapatkan bakteri agens hayati potensial dalam pengendalian penyakit penting padi di antaranya yang disebabkan Pyricularia oryzae, Xanthomnas oryzae pv. oryzae, Rhizoctonia solani, Burkholderia glumae, dan Drechlera oryzae, berdasarkan mekanisme antagonisme, kemampuan menginduksi ketahanan dan mendukung kebugaran tanaman, serta kompatibilitas antaragens hayati. Ralstonia pickettii TT47, Pseudomonas fluorescens P12, Chromobacterium sp. T51118, Bacillus subtilis 451 dan 154, serta Streptomyces sp. T51105 dibuktikan memiliki mekanisme antibiosis dengan menghasilkan metabolit sekunder dan senyawa volatil. Berdasarkan uji produksi enzim kitinolitik Chromobacterium sp. dan Streptomyces sp. memiliki mekanisme lisis. Aktivitas antibiotik R. pickettii dan P. fluorescens tergolong kuat terhadap P. oryzae dengan penekanan secara berurutan sebesar 79.68% dan 77.59% pada uji biakan ganda. Penekanan pertumbuhan miselium P. oryzae dan R. solani pada uji volatil mencapai 100% oleh Chromobacterium sp. Semua agens hayati umumnya mampu menginduksi ketahanan dan mendukung kebugaran tanaman. Uji kompatibilitas menunjukan R. pickettii, P. fluorescens, dan Chromobacterium sp. bersifat kompatibel. Dari hasil penelitian diperoleh tiga bakteri agens hayati dengan kategori unggul, yaitu P. fluorescens P12, R. pickettii TT47, dan Chromobacterium sp. T51118. Ketiganya mampu menekan pertumbuhan patogen, menginduksi ketahanan dan mendukung kebugaran tanaman, memiliki patogen sasaran yang lebih beragam, serta bersifat kompatibel.

Intervensi Pemupukan dan Mikroba terhadap Pertumbuhan, Produksi, dan Mutu Benih Padi IPB 3S di Lahan Rawa Lebak

Swamp land ecology is a potential land to increase the crop production, especially rice. The research was aimed to increase the production and seed quality of IPB 3S rice variety in swamp land ecology. The research was arranged in Factorial Randomized Complete Block Design with three replications. The first factor was dose of Zinc, consist of 0 kg ha-1, 15 kg ha-1, 30 kg ha-1, and 45 kg ha-1. The second factor was seed treatment by probiotic microbial, consist of control, Bacillus sp, Bacillus sp (+), Chromobacterium sp, Chromobacterium sp (+). Zinc fertilization couldn’t increase the yield characters and seed quality of IPB 3S rice variety. Microbia fertilization could increase the highest yield characters (plant height, tillers, productive tillers, panicle length, weiht per plant, and seed weight per grove), and Bacillus microbial increased the seed quality (Vigor index). Interaction of zinc fertilization (15 kg ha-1) and Chromobacterium increased the yield characters (flag leaf length, panicle length, and seed weight per grove), and the interaction of zink fertilization (30 kg ha-1) and Bacillus increased seed quality (vigour index).

A novel antimicrobial protein of the endophytic Bacillus amyloliquefaciens and its control effect against Fusarium chlamydosporum

Fusarium chlamydosporum is the causal agent of stem rot in Jacaranda acutifolia. Bacillus amyloliquefaciens is an endophytic bacterium that shows promising biological control activity against F. chlamydosporum. In this study, B. amyloliquefaciens was cultured in a fermentation broth, and the main antimicrobial substance in the fermentation broth was isolated using the ammonium sulfate precipitation method and purified by DEAE sepharose fast flow weak anion exchange chromatography and sephadex G-50 molecular sieve chromatography. Polyacrylamide gel electrophoresis revealed a single antimicrobial protein with a molecular weight of approximately 29.0 kDa. The antimicrobial protein is a strong antagonist against F. chlamydosporum, leading to mycelial deformity, unclear mycelial septa, and isolated and granulated intracellular protoplasm. The N-terminal eight-amino acid sequence, NH2-Gly-Arg-Pro-Leu-Pro-Leu-Ala-Ala, was determined using the automatic Edman degradation method. BLAST analysis indicated that the amino acid residue sequence at positions 154–161 shows 100% homology to the hypothetical protein of Chromobacterium sp. LK1. However, no known homologous antimicrobial protein was identified, indicating that we have isolated a novel antimicrobial protein.

Expression optimization, purification, and functional characterization of cholesterol oxidase from Chromobacterium sp. DS1.

Cholesterol oxidase is a bifunctional bacterial flavoenzyme which catalyzes oxidation and isomerization of cholesterol. This valuable enzyme has attracted a great deal of attention because of its wide application in the clinical laboratory, synthesis of steroid derived drugs, food industries, and its potentially insecticidal activity. Therefore, development of an efficient protocol for overproduction of cholesterol oxidase could be valuable and beneficial in this regard. The present study examined the role of various parameters (host strain, culture media, induction time, isopropyl ß-D-1-thiogalactopyranoside concentration, as well as post-induction incubation time and temperature) on over-expression of cholesterol oxidase from Chromobacterium sp. DS1. Applying the optimized protocol, the yield of recombinant cholesterol oxidase significantly increased from 92 U/L to 2115 U/L. Under the optimized conditions, the enzyme was produced on a large-scale, and overexpressed cholesterol oxidase was purified from cell lysate by column nickel affinity chromatography. Km and Vmax values of the purified enzyme for cholesterol were estimated using Lineweaver-Burk plot. Further, the optimum pH and optimum temperature for the enzyme activity were determined. This study reports a straightforward protocol for cholesterol oxidase production which can be performed in any laboratory.

Anti-hypertensive mechanisms of cyclic depsipeptide inhibitor ligands for Gq/11 class G proteins

Augmented vasoconstriction is a hallmark of hypertension and is mediated partly by hyper-stimulation of G protein couple receptors (GPCRs) and downstream signaling components. Although GPCR blockade is a key component of current anti-hypertensive strategies, whether hypertension is better managed by directly targeting G proteins has not been thoroughly investigated. Here, we tested whether inhibiting Gq/11 proteins in vivo and ex vivo using natural cyclic depsipeptide, FR900359 (FR) from the ornamental plant, Ardisia crenata, and YM-254890 (YM) from Chromobacterium sp. QS3666, or it’s synthetic analog, WU-07047 (WU), was sufficient to reverse hypertension in mice. All three inhibitors blocked G protein-dependent vasoconstriction, but to our surprise YM and WU and not FR inhibited K+-induced Ca2+ transients and vasoconstriction of intact vessels. However, each inhibitor blocked whole-cell L-type Ca2+ channel current in vascular smooth muscle cells. Subcutaneous injection of FR or YM (0.3 mg/kg, s.c.) in normotensive and hypertensive mice elicited bradycardia and marked blood pressure decrease, which was more severe and long lasting after the injection of FR relative to YM (FRt1/2 ≅ 12 h vs. YMt1/2 ≅ 4 h). In deoxycorticosterone acetate (DOCA)-salt hypertension mice, chronic injection of FR (0.3 mg/kg, s.c., daily for seven days) reversed hypertension (vehicle SBP: 149 ± 5 vs. FR SBP: 117 ± 7 mmHg), without any effect on heart rate. Our results together support the hypothesis that increased LTCC and Gq/11 activity is involved in the pathogenesis of hypertension, and that dual targeting of both proteins can reverse hypertension and associated cardiovascular disorders.

Control of Ginseng Damping-Off Disease Using Chitinolytic Bacterial Mixtures

An effective bioformulation of mixtures of chitin-degrading bacteria has been used successfully to control plant diseases and nematodes. In this study, the bioformulation approach was assessed to control dampingoff disease of ginseng. In pot experiments with soils infested with dapming-off pathogens of ginseng, rootdrenchings of Chrobacterium sp. C-61, Lysobacterium enzymogenes C-3, and mixture of two bacterial strains grown in chitin minimal medium were signficantly increased emergence of seeds and reduced dampingoff disease incidence of seedlings. Efficacy of the bioformulated product depended on the dose and timing of application. In two-year-old ginseng field, the high control efficacies were achieved by soil drenching of two times with an undiluted product or three times with a 10-fold diluted product. In a To-jik nursery (self soil nursery), biocontrol efficacy of the undiluted product against damping-off disease were similar to that of a seed dressing with fungicide, Tolclofos-methyl WP. These results suggest that the bioformulated product containing Chromobacterium sp. C-61 and L. enzymogenes C-3 could be an effective approach to control of ginseng damping-off disease.

PHA synthase (PhaC): interpreting the functions of bioplastic-producing enzyme from a structural perspective.

Polyhydroxyalkanoates (PHAs) are biopolymers synthesized by a wide range of bacteria, which serve as a promising candidate in replacing some conventional petrochemical-based plastics. PHA synthase (PhaC) is the key enzyme in the polymerization of PHA, and the crystal structures were successfully determined using the catalytic domain of PhaC from Cupriavidus necator (PhaCCn-CAT) and Chromobacterium sp. USM2 (PhaCCs-CAT). Here, we review the beneficial mutations discovered in PhaCs from a structural perspective. The structural comparison of the residues involved in beneficial mutation reveals that the residues are near to the catalytic triad, but not inside the catalytic pocket. For instance, Ala510 of PhaCCn is near catalytic His508 and may be involved in the open-close regulation, which presumably play an important role in substrate specificity and activity. In the class II PhaC1 from Pseudomonas sp. 61-3 (PhaC1Ps), Ser325 stabilizes the catalytic cysteine through hydrogen bonding. Another residue, Gln508 of PhaC1Ps is located in a conserved hydrophobic pocket which is next to the catalytic Asp and His. A class I, II-conserved Phe420 of PhaCCn is one of the residues involved in dimerization and its mutation to serine greatly reduced the lag phase. The current structural analysis shows that the Phe362 and Phe518 of PhaC from Aeromonas caviae (PhaCAc) are assisting the dimer formation and maintaining the integrity of the core beta-sheet, respectively. The structure-function relationship of PhaCs discussed in this review will serve as valuable reference for future protein engineering works to enhance the performance of PhaCs and to produce novel biopolymers.