Screening of three phenol-degrading bacteria for copper bioremoval of copper

Aim: Potential microbial isolates for bioremoval of copper were collected from phenolic and heavy metal-contaminated soils and screened in copper-containing medium for determining the maximum tolerance level for copper. Methodology: Bioremoval of copper was assessed using sodium diethyl dithiocarbamate assay. Physical and cultural conditions influencing copper bioremoval such as initial concentration, biomass dosage (inoculum volume), temperature and pH were optimised via one-factor-at-a-time. Results: The highest maximum tolerance level was displayed by Serratia sp. AQ5-03 at 600 mg l-1, while for Alcaligenes sp. AQ5-02 and Pseudomonas sp. AQ5-04 it was 500 mg l-1. The highest bioremoval for Alcaligenes sp. AQ5-02, Serratia sp. AQ5-03 and Pseudomonas sp. AQ5-04 was achieved at 20, 50 and 75 mg l-1, respectively. The optimum biomass dosage (inoculum volume) for both Serratia sp. AQ5-03 and Pseudomonas sp. AQ5-04 were 15%, whereas it was 10% for Alcaligenes sp. AQ5-02. The results also revealed that maximum bioremoval was achieved at pH 6 at an optimum temperature of 20°C for both Alcaligenes sp. AQ5-02 and Pseudomonas sp. AQ5-04, while Serratia sp. AQ5-03 showed optimum removal at pH 7 and at 30°C temperature. The maximum bioremoval efficiency for Alcaligenes sp. AQ5-02, Serratia sp. AQ5-03 and Pseudomonas sp were found to be 62, 57 and 70%, respectively. Interpretation: The results indicate that Alcaligenes sp. AQ5-02, Serratia sp. AQ5-03, Pseudomonas sp. AQ5-04 can be utilised as bioremoval agent since it possessed the highest bioremoval efficiency for copper remediation.

Phenotypic Characterization and Synthesis of Extracellular Catecholase from a Newly Isolated Bacterium Pseudomonas sp. BSC-6

Abstract Catecholase (EC 1.10.3.1), an oxidoreductase enzyme is a key member of polyphenol oxidase family which catalyze the degradation of catechol. This enzyme possesses vast applications in diverse areas and is found in bacteria, fungi, mushrooms, higher plants, arthropods, amphibians and mammals. Catechol, a phenolic compound, is used as a starting material in the synthesis of various industrial compounds such as inhibitors, antioxidants, pesticides etc. The release of this phenolic compound in the environment causes toxicity to both flora and fauna. In the present studies, emphasis has been laid on isolation, screening and characterization of catechol degrading bacterium coupled with synthesis of catecholase enzyme. Further, the selected isolated strain was phenotypically characterized and was found to be member of genus Pseudomonas. Among all the isolates, BSC-6 was found as best isolate with maximum extracellular catecholase activity of 152.32 IU/L obtained after scale up studies. The herein synthesized bacterial catecholase may be employed for wide applications particularly in bioremediation of phenol enriched polluted sites.

Enhancement the Biodegradation of Sodium Dodecyl Sulfate by Pseudomonas aeruginosa and Pseudomonas otitidis Isolated from Waste Water in Saudi Arabia

Sodium dodecyl sulfate, (SDS) is an anionic surfactant that widely utilized in industry and households. Which represent toxic effects to the health and aquatic organisms. The bacterial strains Pseudomonas aeruginosa and Pseudomonas otitidis were isolated from the water samples from waste disposal sites (Taif Governate, Kingdom of Saudi Arabia). So, in the present study, we have made an attempt to improve the biodegradation of SDS by Pseudomonas aeruginosa and Pseudomonas otitidis by different methods such as mutation (Physically and chemically), physically by exposure of bacterial strains to ultraviolet radiation (UV) and chemically by using chemicals such as ethidium bromide (EtBr), also biodegradation rate of SDS can be increased by immobilization technique. The bacterial strains were immobilized in alginate beads, and its SDS degradation efficiency was observed to increase many fold than free strains.

Extracellular synthesis of silver nanoparticles by Pseudomonas sp. THG-LS1.4 and their antimicrobial application / 药物分析学报

Silver nanoparticles (AgNPs) are known to have bacteriostatic and bactericidal effects. The present study highlights the extracellular synthesis of AgNPs and its antibacterial properties. The AgNPs were synthesized using Pseudomonas sp. THG-LS1.4 strain which had been isolated from soil. The AgNPs werecharacterized by field emission-transmission electron microscopy (FE-TEM), X-ray diffraction (XRD),Fourier transform-infrared (FT-IR) spectroscopy, and particle size distribution (DLS). The AgNPs displayed maximum absorbance at 412 nm and were irregular in shape ranging from 10 to 40 nm. The XRD spectroscopy results demonstrated the crystalline nature of nanoparticles. The AgNPs showed antimicrobial activity against Bacillus cereus, Staphylococcus aureus, Candida tropicalis, Vibrio parahaemolyticus,Escherichia coli and Pseudomonas aeruginosa. Furthermore, the AgNPs were also evaluated for their increased antibacterial activities with various antibiotics against Escherichia coli, Pseudomonas aeruginosa and Salmonella enterica. Additionally, AgNPs showd biofilm inhibition activity. The biosynthesized AgNPs were found to be a potent agent against tested pathogens. More importantly, we highlight the applications of AgNPs as an antimicrobial agent.

Regional analysis of potential polychlorinated biphenyl degrading bacterial strains from China

ABSTRACT Polychlorinated biphenyls (PCBs), the chlorinated derivatives of biphenyl, are one of the most prevalent, highly toxic and persistent groups of contaminants in the environment. The objective of this study was to investigate the biodegradation of PCBs in northeastern (Heilongjiang Province), northern (Shanxi Province) and eastern China (Shanghai municipality). From these areas, nine soil samples were screened for PCB-degrading bacteria using a functional complementarity method. The genomic 16S rDNA locus was amplified and the products were sequenced to identify the bacterial genera. Seven Pseudomonas strains were selected to compare the capacity of bacteria from different regions to degrade biphenyl by HPLC. Compared to the biphenyl content in controls of 100%, the biphenyl content went down to 3.7% for strain P9-324, 36.3% for P2-11, and 20.0% for the other five strains. These results indicate that a longer processing time led to more degradation of biphenyl. PCB-degrading bacterial strains are distributed differently in different regions of China.

Screening, stability and antibacterial potential of rhamnolipids from Pseudomonas sp., isolated from hydrocarbon contaminated soil.

Surfactant plays an important role in industrial application such as oil recovery, lubricants and emulsifier. But chemical surfactants are toxic to human and other small animals. In recent years, biological based surfactants have gained increasing attention due to their ecofriendly in nature. The present study was focused to isolate biosurfactant producing bacteria, their stability and antibacterial ability from hydrocarbon contaminated and uncontaminated soil collected from different locations in Kanchipuram, Tamil Nadu, India. Biosurfactant producing bacteria were screened by following the haemolytic activity, drop collapsing test, emulsion against kerosene and was further confirmed through surface activity. The stability of the biosurfactant was determined by different physic-chemical conditions like pH, temperature and salinity. A total of 37 strains were selected in three different samples based on cultural characters and finally only 7 strains were confirmed as positive for biosurfactant. Among these strain H11 was considered as potential based on emulsification index (44%), surface activity (34.45 x 10-3 nm-1) and surface tension (23.17 x 10-3 nm-1) and was identified as Pseudomonas sp. The emulsification activity was stable at broad range of pH (4-12), temperature (4-120°C) and salt concentration (0-10%). The biosurfactant was further characterized in HPLC and one major peak was observed at a retention time of 2.033. The antibacterial activity of biosurfactant was high against gram positive pathogenic bacteria than gram negative bacteria. The rhamnolipid produced Pseudomonas sp. may be used as a tool to manage the oil pollution and to control the disease causing bacteria.

Degradation of 2,4,6-trinitrotoluene by P. aeruginosa and characterization of some metabolites

Degradation of 2,4,6-trinitrotoluene (TNT), a nitroaromatic explosive found in the soil and ground water, was investigated using Pseudomonas aeruginosa in in vitro experiments. Biodegradable abilitiy of this bacteria was performed with 50 and 75 mg L−1 TNT concentrations in a defined liquid medium for 96 h time period. Treatment of TNT in supernatant samples taken at 0, 6, 12, 24, 48, 72 and 96 h from agitated vessels was followed by reverse-phase high-performance liquid chromatography (HPLC). In cultures supplemented with 50 and 75 mgL−1 TNT, after 96 h of incubation 46% and 59% reduction were detected respectively. Two metabolites as degradation intermediates with nitrite release into the medium, 2,4-dinitrotoluene (2,4-DNT) and 4-aminodinitrotoluene (4-ADNT), were elucidated by thin layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS). These findings clearly indicate that Pseudomonas aeruginosa can be used in bioremediation of TNT contaminated sites.

Efecto de un bioinoculante a partir de consorcios microbianos nativos fosfato solubilizadores, en el desarrollo de pastos Angleton (Dichantium aristatum) / Effect of bio-inoculant from microbial consortia phosphate solubilizing natives in development of pastures (Dichantium aristatum)

El objetivo fue evaluar la capacidad solubilizadora de fosfatos de consorcios formados por bacterias nativas de los géneros Burkholderia cepacia, Pseudomonas sp, Pseudomonas luteola y Pantoea sp, con el fin de encontrar el más eficiente. Se realizaron pruebas de antagonismo entre las cepas y se formaron consorcios probando todas las combinaciones posibles en las concentraciones de 10(6), 10(7), 10(8) UFC/mL. Se realizaron evaluaciones cualitativas y cuantitativas de la solubilización de fosfatos y teniendo en cuenta éstos resultados, se preparó un bioinoculante el cual fue evaluado en semillas de plantas de pasto angleton (Dichantium aristatum) a escala de laboratorio, utilizando un diseño estadístico completamente al azar (DCA) con 3 tratamientos y 5 repeticiones: Tratamiento 1 semillas (control), Tratamiento 2, semillas tratadas con el consorcio de microorganismos seleccionado y Tratamiento 3, semillas tratadas con fertilizantes comerciales DAP y Urea. Se evaluaron las variables número de hojas, área foliar, longitud de la planta, longitud de la raíz y peso seco de todas las plantas. Los resultados de la prueba de antagonismo indicaron que no existe inhibición en el crecimiento de las cepas evaluadas, por lo tanto se formaron consorcios los cuales mostraron mayor eficiencia en la solubilización del fósforo, destacándose el consorcio formado por Pantoea sp + Pseudomonas sp a una concentración de 10(8) UFC/mL y con índices de solubilización de 5,3 y 842 ppm. En las plantas se evidenció un incremento significativo en los parámetros peso seco y área foliar usando el consorcio microbiano, indicando mayor beneficio en comparación con el control.

The objective was to evaluate the ability of phosphate solubilizing consortium of native bacteria of the genusBurkholderia cepacia, Pseudomonas sp, Pseudomonas luteola and Pantoea sp, in order to find the most efficient. Antagonism tests were conducted between strains and consortia were formed using all possible combinations in the concentrations of 10(6), 10(7), 10(8) CFU / mL. Qualitative and quantitative determinations of the solubilization of phosphates were performed and considering these results, was prepared a bio-inoculant which was evaluated in plant seeds of grass angleton (Dichantium aristatum) laboratory scale, using a statistical completely randomized design (CRD) with 3 treatments and 5 repetitions: control Treatment 1 seeds; Treatment 2, seeds treated with the consortium of microorganisms selected and Treatment 3, seeds treated with commercial fertilizers DAP and Urea. The parameters, number of leaves, leaf area, plant length, root length and dry weights of all plants, were evaluated. The test results indicated that there is no antagonism inhibition in the growth of the strains tested thus formed consortia which showed greater efficiency phosphorus solubilization, highlighting the consortium of Pantoea sp + Pseudomonas sp at a concentration 10(8)CFU / mL and 5.3 solubilization rates and 842 ppm. In plants showed a significant increase in dry weight and leaf area parameters, indicating greater benefit with respect to the control treatment.

Efecto de rizobacterias promotoras de crecimiento vegetal solubilizadoras de fosfato en Lactuca sativa cultivar White Boston / Effect of plant growth promoting rhizobacteria phosate solubilizing Lactuca sativa cultivar White Boston

En las últimas décadas, la agricultura colombiana se ha visto afectada por la reducción de la productividad en las zonas hortícolas, el incremento de los costos de producción y la dependencia del uso de productos químicos, produciendo un daño irreversible al medio ambiente y la calidad de vida de productores y consumidores. El objetivo de investigación fue evaluar el efecto de rizobacterias promotoras del crecimiento vegetal del género Pseudomonas sp. sobre Lactuca sativa cultivar White Boston como solubilizadoras de roca fosfórica. El estudio se realizó en el Centro de Investigación Tibaitatá (Corpoica) ubicado en Mosquera (Cundinamarca-Colombia). Los resultados demostraron que las cepas tienen la capacidad intrínseca para solubilizar fuentes de fósforo de baja solubilidad como la roca fosfórica. La aplicación de inoculantes con base en las cepas: Pseudomonas fluorescens FR1, Pseudomonas sp., UVLO27 y Pseudomonas sp. LEAV18 arrojaron los mejores resultados. Las cepas Pseudomonas sp. FR2, UVLO27 y K35, tienen la capacidad de producir índoles y sideróforos. El experimento en invernadero evidenció que las cepas Pseudomonas fluorescens FR1, Pseudomonas sp. FR2 y UVLO27 incrementaron de manera significativa (P<0.05) la biomasa y el desarrollo de las plantas. El uso de rocas fosfóricas representa una alternativa económica y ecológica viable, en sistemas de agricultura sostenible.

In the last decades, Colombian agriculture has been affected by the reduction in productivity in horticultural areas, increase in production costs and the dependence of chemical products usage, causing and irreversible damage to environment and producers and consumers life quality. The aim of this research was to evaluate the effect of plant growth promoting rhizobacteria of the genus Pseudomonas sp. under Lactuca sativa cultivar White Boston as phosphate rock solubilizing bacteria. The study took place in the Research Centre Tibaitatá-Corpoica, located in Mosquera (Cundinamarca-Colombia). Results demonstrated that the strains have an intrinsic capacity to solubilize low solubility phosphorus sources as phosphate rock. Inoculants application based on: Pseudomonas fluorescensFR1, Pseudomonas sp., UVLO27 and Pseudomonas sp. LEAV18 strains displayed the best results. The strains Pseudomonas sp. FR2, UVLO27 and K35, are capable of producing indoles and siderophores. The green house experiment showd that strain Pseudomonas fluorescens FR1, Pseudomonas sp. FR2 of phosphate rocks represents a viable economic and ecological alternative in sustainable agriculture systems.

In-vitro antibacterial activity of coral reef associated bacteria and optimization of bioactive metabolite production.

This study reports the antibacterial activity of coral reef associated bacteria against bacterial pathogens and optimization of metabolite production. Twelve morphologically different bacterial were isolated from stony coral reef collected from Rameshwaram coastal area, Tamil Nadu. Cell free supernatant of all the bacterial isolates were tested against Staphylococcus aureus, Bacillus cereus, Salmonella typhi, Escherichia coli, and Klebsiella pneumoniae by agar well diffusion method. Of the 12 isolates tested, seven isolates showed antibacterial activity again at least one of the test organisms with the zone of inhibition in the range of 9-14 mm. The antibacterial compounds were extracted from the cell free supernatant using ethyl acetate and tested for antibacterial activity. In diffusion method, crude extract from strain RC12 showed 11-17 mm inhibition against all the test pathogens and the same was selected for optimization studies. Effect of culture conditions and medium components such as different carbon, nitrogen, mineral, pH, temperature on antibacterial metabolite production was studied by adopting one-factor-at-a- time method. The metabolite production was influenced by lactose, ammonium sulphate, K2HPO4 while the optimal cultivation conditions were pH 7 and 37°C. The potent strain RC12 was identified as Pseudomonas sp based on their phenotypic and biochemical characteristics. The finding of the present study concludes that coral reef bacteria found to be the best source for bioactive metabolites with broad spectrum activity.

PCR based detection of gyrB2 gene from Pseudomonas sp. affected human clinical isolates.

Detection of virulence gene is a key component in determining the pathogenicity of any isolates because these genes act multi-functionally and multi-factorially. Gyrase specific gene primer in combination of PCR technology allows precise detection of DNA gyrase subunit B2 gene (gyrB2) from different virulent microorganisms. In the present study, forward and reverse primers with a length of 20bp for both were used for detection of gyrB2 genes in clinical isolates of Pseudomonas sp. collected from patients suffering from urinary tract infection (UTI). A total of 12 isolates of Pseudomonas sp. viz., Ps1, Ps2, Ps3, Ps4, Ps5, Ps6, Ps7, Ps8, Ps9, Ps10, Ps11 and Ps12 were used in present study in which gyrB2 gene amplified in all 12 isolates and gave the expected 1130bp PCR product after visualization under gel documentation system in 1.2% agarose gel. This PCR was outstanding in the detection of gyrB2 gene in urinary tract infected patients caused by Pseudomonas sp. species.

PCR based detection of gyrB2 gene from Pseudomonas sp. affected human clinical isolates.

Detection of virulence gene is a key component in determining the pathogenicity of any isolates because these genes act multi-functionally and multi-factorially. Gyrase specific gene primer in combination of PCR technology allows precise detection of DNA gyrase subunit B2 gene (gyrB2) from different virulent microorganisms. In the present study, forward and reverse primers with a length of 20bp for both were used for detection of gyrB2 genes in clinical isolates of Pseudomonas sp. collected from patients suffering from urinary tract infection (UTI). A total of 12 isolates of Pseudomonas sp. viz., Ps1, Ps2, Ps3, Ps4, Ps5, Ps6, Ps7, Ps8, Ps9, Ps10, Ps11 and Ps12 were used in present study in which gyrB2 gene amplified in all 12 isolates and gave the expected 1130bp PCR product after visualization under gel documentation system in 1.2% agarose gel. This PCR was outstanding in the detection of gyrB2 gene in urinary tract infected patients caused by Pseudomonas sp. species.

A novel approach for the microbial production and optimization of gold nanoparticles- an alternate approach to chemical synthesis.

Nanotechnology is the application of science to control matter at the molecular level. A nanometer (nm) is one billionth of a meter, or roughly the length of three atoms side by side. A nanoparticle is a microscopic particle with atleast one dimension less than 100 nm. The applilcation of nanoscale materials and structures, usually ranging from 1 to 100 nanometer are an emerging area of nanoscience and nanotechnology. Gold nanoparticles, in particular, are of interest, due to their stability under atmospheric conditions, resistance to oxidation and biocompatibility. Microorganisms as possible eco–friendly nanofactories can exert control over size, morphology, composition and crystallographic orientation of the as–prepared metal nanostructured particles. In the area of nanotechnology, the development of techniques for the controlled synthesis of metal nanoparticles of well defined size, shape and composition is a big challenge. This work was highly focused on the Gold nanoparticles production from Pseudomonas sp. and concentrating the work towards the production at controlled size by means of various parameter optimization studies like pH, temperature and concentration. The optimization work was characterized by means of TEM. With the results of TEM, the small sized nanoparticle of about 10nm was observed at pH of 9 and 12nm was produced at the pH of 3. Low temperature of 25oC favored the small size nanoparticle at a concentration of 250 mg/l using HAuCl4.

Poly--hydroxybutyrate production by Pseudomonas sp. RZS 1 under aerobic and semi-aerobic condition.

Pseudomonas sp. RZS1 was isolated from distillery effluent and identified based on phenotypic characters and 16s rRNA sequencing. It accumulated optimum amount (703.79 g/mg of biomass) of poly--hydroxybutyrate (PHB) under aerobic process of fermentation and 75 g/mg of biomass under the anaerobic process of fermentation. Aerobic fermentation yielded 9.3-fold more PHB than semi-aerobic fermentation. Acetone alcohol method proved to be the best suitable recovery method as it gave 703.79 g PHB per mg of biomass with a percentage recovery yield of 70.37. It started to accumulate PHB at the end of lag phase (from 6 h of incubation). Optimum amount of PHB (20 g/ml) was reported during early stationary phase (30 h of incubation). Extracted PHB showed two peaks, minor one at 248 nm and major one at 365 nm. IR spectra revealed the presence of functional groups characteristics of PHB.

Formação in vitro de bioflme por Pseudomonas aeruginosa e Staphylococcus aureus na superfície de canetas odontológicas de alta rotação / In vitro biofilm formation by Pseudomonas aeruginosa and Staphylococcus aureus on the surface of high-speed dental handpieces

Em consultórios odontológicos, são utilizadas canetas de alta rotação que funcionam conectadas a circuitos de água. Estudos já demonstraram contaminação microbiana em amostras de água coletada de tubulações desses circuitos. Durante sua utilização, essas canetas entram em contato com a microbiota oral, o que pode favorecer a formação de biofilme em sua superfície e influir na qualidade e na segurança dos procedimentos. O objetivo deste trabalho foi avaliar a formação in vitro de biofilme na superfície de canetas odontológicas utilizando-se Pseudomonas aeruginosa e Staphylococcus aureus. Os experimentos foram executados em fragmentos de alumínio provenientesdo corte de canetas odontológicas e a formação do biofilme foi verificada pela contagem de bactérias viáveis (CBV)e por microscopia eletrônica de varredura (MEV). O número de células aderidas atingiu 9 × 106 ufc.cm–2 paraPseudomonas aeruginosa e 6 × 108 ufc.cm–2 para Staphylococcus aureus. A MEV mostrou a adesão de Pseudomonasaeruginosa e Staphylococcus aureus aos fragmentos e a presença de matriz polimérica a partir do sexto dia deincubação. Também foi testada a produção de biofilme por essas bactérias na superfície de placas de poliestireno, pelo método do Cristal Violeta. Ambos os micro-organismos exibiram valores de absorbância superiores ao ponto de corte estabelecido, indicando resultados positivos. Foi demonstrada, ainda, a capacidade de ambas as bactériasproduzirem cápsula, utilizando-se o método do Ágar Vermelho Congo. Nas condições testadas, os experimentosrealizados neste trabalho mostraram a formação in vitro de biofilme na superfície de material proveniente decanetas odontológicas, um evento importante considerando-se que sua presença representa um potencial risco para o estabelecimento de contaminação cruzada.

High-speed handpieces connected to running water circuits are used in dental offices. Studies have shown microbial contamination in water samples collected from the tubing of these circuits. Handpieces come in contact with oral microorganisms during use, which can promote the formation of biofilm on the handpiece and affect procedural quality and safety. The aim of this study was to evaluate in vitro biofilm formation on the surface of high-speed dental handpieces using Pseudomonas aeruginosa and Staphylococcus aureus. The assays were performed on aluminum fragments cut from dental handpieces and biofilm formation assessed by viable bacteria counting (VBC) and scanning electron microscopy (SEM). The number of adhered cells was 9 × 10(6)ufc.cm(-2) for Pseudomonas aeruginosa and 6 × 10(8)ufc.cm(-2) for Staphylococcus aureus. SEM showed the adherence of Pseudomonas aeruginosa and Staphylococcus aureus to handpiece fragments and the presence of a polymer matrix after six days of incubation. We also tested biofilm production by these bacteria on the surface of polystyrene plates using the Crystal Violet method. Both microorganisms displayed absorbance values above the established cut-off point, indicating positive results. The ability of these bacteria for capsule (slime) production was shown using the Congo Red Agar method. Within the limits of these experiments, this study demonstrated in vitro biofilm formation on the surface of material from dental handpieces, indicating a potential cross contamination risk.

Cadmium tolerance and antibiotic resistance of Pseudomonas sp. isolated from water, sludge and fish raised in wastewater-fed tropical ponds.

The numbers of Pseudomonas sp. isolated were counted in samples collected from water, sludge and intestine of fishes raised in different wastewater ponds along an effluent gradient in a sewage treatment plant. Total fish yield in the last maturation pond increased by 73% over the yield in first maturation pond or facultative pond. The number of Pseudomonas sp. isolated from the intestine of the tilapia (Oreochromis mssambicus) raised in facultative pond, was more than three times the counts (7.22 × 108/g) observed in the last maturation pond (2.025 × 108/g). The effective lethal concentration of cadmium for Pseudomonas sp. isolated from the intestine of the tilapia was 0.6 mM and 0.08-0.09 mM when the fish was procured from facultative pond and last maturation pond, respectively. The Pseudomonas sp. isolated from the intestine of the tilapia did not have resistance to any of the ten antibiotics tested. However, the bacterium isolated from raw sewage, water and sediment of the anaerobic pond was resistant to seven out of ten antibiotics tested.

Inhibition of shrimp pathogenic vibrios by extracellular compounds from a proteolytic bacterium Pseudomonas sp. W3 / Inhibición de vibrios patógenos del camarón por compuestos extracelulares de una bacterias proteolítica Pseudomonas sp.W3

Pseudomonas sp. W3, a bacterium known to produce an extracellular alkaline protease, secreted secondary metabolites that inhibited pathogenic bacteria responsible for shrimp luminous vibriosis disease. Antivibrio compounds in the culture supernatant or culture filtrates (0.45 um and 0.22 um) of the isolate W3 were tested using an agar well diffusion method on a number of pathogenic vibrios. Vibrio harveyi PSU 2015 a pathogenic isolate was the most sensitive strain. The effectiveness of preparations from the isolate W3 against V. harveyi PSU 2015, and V. cholerae PSSCMI 0062 was in the order of culture supernatant > 0.45 um culture filtrate > 0.22 um culture filtrate. These extracellular antivibrio compounds also lysed both dead and living cells of V. harveyi PSU 2015. Results of the partial characterization tests indicated that there was some particulate antivibrio compound that was destroyed by treatment with enzymes particularly alpha-chymotrypsin, autoclaving at 121ºC for 15 min and was mostly removed by filtration through a 0.22 µm filter. Most of the inhibitory compounds were of small molecular weight able to pass through a 0.22 um filter and were resistant to treatment with various enzymes, pH values between 4-8 and temperatures up to 121ºC for 30 min. The optimum pH for the antivibrio activity in the 0.45 um culture filtrate was between pH 6-7.

Isolation and characterization of an acrylamide-degrading Antarctic bacterium.

The presence of acrylamide in the environment poses a threat due to its well known neurotoxic, carcinogenic and teratogenic properties. Human activities in various geographical areas are the main anthropogenic source of acrylamide pollution. In this work, an acrylamide-degrading bacterium was isolated from Antarctic soil. The physiological characteristics and optimum growth conditions of the acrylamide-degrading bacteria were investigated. The isolate was tentatively identified as Pseudomonas sp. strain DRYJ7 based on carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. The results showed that the best carbon sources for growth was glucose and sucrose with no significant difference in terms of cellular growth between the two carbon sources (p>0.05). This was followed by fructose and maltose with fructose giving significantly higher cellular growth compared to maltose (p<0.05). Lactose and citric acid did not support growth. The optimum acrylamide concentration as a nitrogen source for cellular growth was at 500 mgl-1. At this concentration, bacterial growth showed a 2-day lag phase before degradation took place concomitant with an increase in cellular growth. The isolate exhibited optimum growth in between pH 7.5 and 8.5. The effect of incubation temperature on the growth of this isolate showed an optimum growth at 15°C. The characteristics of this isolate suggest that it would be useful in the bioremediation of acrylamide.

Breeding of High Lipolytical Bacteria by Acclimation to Jatropha Oil and Resultant Strain-catalyzed Esterification Reaction / 微生物学通报

A strain, Pseudomonas sp. X-2-45, with high and stable lipolytical activity was screened by continuously subculturing a lipase-producing bacterium P. sp. LP-1 in culture medium containing Jatropha oil as a sole carbon source. Its hydrolytic activity was 29.79 U/mL, which was increased by 288% as compared to that of parent strain. Furthermore, the growth and lipase synthesis of X-2-45, its catalytic ability to hydrolyze vegetable oils, as well as ester synthesis between fatty acids and organic alcohols were studied. Results showed that rates of bacterial growth and lipase synthesis were significantly raised. Bacterial biomass and lipase activity reached the highest level after 30 h of incubation. Moreover, growth stationary period was prolonged and lipase produced exhibited good stability in culture media during incubation period. Hydro- lytic activity of P. sp. X-2-45 lipase toward Jatropha oil was increased by 378% as compared to parent strain, suggesting that acclimation to Jatropha oil was an effective approach for improving substrate selectivity oflipase. Finally, results of ester synthesis catalyzed by P. sp. X-2-45 lipase indicated that this lipase could catalyze esterification reactions between lauric acid and n-butanol, n-octanol, 1-dodecanol or glycerol, palmitic acid or stearic acid and methanol, n-octanol, 1-dodecanol or glycerol, oleic acid and methanol, n-butanol, n-octanol, 1-dodecanol or glycerol.

Construction of Pseudomonas sp. M18 pqsR Mutant and Its Regulation on Plt Biosynthesis / 微生物学通报

Pseudomonas sp. M18 is one of plant growth-promoting rhizobacteria capable of producing two kinds of anti-fungal agents: phenazine-1-carboxilic acid (PCA) and pyoluteorin (Plt). The pqsR gene, which encodes a LysR family member PqsR, was amplified from chromosomal genome of strain M18. Using the homologous recombination technique, a chromosomal pqsR inactivated mutant strain M18PRG was constructed in Pseudomonas sp. M18. To study the effect of pqsR gene on Plt biosynthesis, the dynamic curves of Plt production by strains M18 and M18PRG was measured in KMB media. As a result, Plt production of the pqsR mutant was three to four folds higher than that of its parent strain M18. The Plt production was restored to the wild-type level when strain M18PRG was complemented with pqsR gene in trans. The regulation of pqsR gene on Plt production was further confirmed by the pltA′-′lacZ translational fusion analysis. These results indicate that pqsR gene negatively controls the Plt biosynthesis. Additionally, by analyzing the growth curves of wild type strain M18 and pqsR mutant, wecan readily find that PqsR has a negative influence on cell growth. It was also shown that the production of red pigments in strain M18 required the expression of pqsR gene. In conclusion, the data presented in this study clearly demonstrate that PqsR acts as a global regulator involved in many physiological activities in Pseudomonas sp. M18.