Oxidative foliar photo-necrosis produced by the bacteria Pseudomonas cedrina

BACKGROUND: Although bioactive metabolites capable of causing oxidative photo-necrosis in plant tissues have been identified in fungi, little is known about this type of mechanism in bacteria. These metabolites act as photosensitizers that generate reactive oxygen species (ROS) capable of causing damage to cells. In addition, these metabolites can pass into an energetically excited state when they receive some luminous stimulus, a condition in which they interact with other molecules present in the environment, such as molecular oxygen (O2), also known as triplet oxygen (3 O2), generating ROS. RESULTS: The suspension of the bacterial culture of Pseudomonas cedrina was shown to produce foliar necrosis in papaya leaves (Carica papaya L.) only in the presence of sunlight, which is evidence of photosensitizing mechanisms that generate singlet oxygen (1 O2). From the chemical study of extracts obtained from this bacteria, 3-(4-(2-carboxipropyl) phenyl) but-2-enoic acid (1) was isolated. This compound, in the presence of light and triplet oxygen (3 O2), was able to oxidize ergosterol to its peroxide, since it acted as a photosensitizer producing 1 O2, with which it was corroborated that a photosensitization reaction occurs, mechanism by which this bacterium could prove to cause oxidative foliar photo-necrosis. CONCLUSIONS: P. cedrina was able to induce oxidative foliar photo-necrosis because of its potential ability to produce photosensitizing metabolites that generate singlet oxygen in the plants it colonizes. Based on the above, it can be proposed that some bacteria can cause oxidative foliar photo-necrosis as an important mechanism in the pathogenesis of host species.

Alginate overproduction and biofilm formation by psychrotolerant Pseudomonas mandelii depend on temperature in Antarctic marine sediments

Background: In recent years, Antarctica has become a key source of biotechnological resources. Native microorganisms have developed a wide range of survival strategies to adapt to the harsh Antarctic environment, including the formation of biofilms. Alginate is the principal component of the exopolysaccharide matrix in biofilms produced by Pseudomonas, and this component is highly demanded for the production of a wide variety of commercial products. There is a constant search for efficient alginate-producing organisms. Results: In this study, a novel strain of Pseudomonas mandelii isolated from Antarctica was characterized and found to overproduce alginate compared with other good alginate producers such as Pseudomonas aeruginosa and Pseudomonas fluorescens. Alginate production and expression levels of the alginate operon were highest at 4°C. It is probable that this alginate-overproducing phenotype was the result of downregulated MucA, an anti-sigma factor of AlgU. Conclusion: Because biofilm formation is an efficient bacterial strategy to overcome stressful conditions, alginate overproduction might represent the best solution for the successful adaptation of P. mandelii to the extreme temperatures of the Antarctic. Through additional research, it is possible that this novel P. mandelii strain could become an additional source for biotechnological alginate production.

Draft genome sequence of a caprolactam degrader bacterium: Pseudomonas taiwanensis strain SJ9

Abstract Pseudomonas taiwanensis strain SJ9 is a caprolactam degrader, isolated from industrial wastewater in South Korea and considered to have the potential for caprolactam bioremediation. The genome of this strain is approximately 6.2 Mb (G + C content, 61.75%) with 6,010 protein-coding sequences (CDS), of which 46% are assigned to recognized functional genes. This draft genome of strain SJ9 will provide insights into the genetic basis of its caprolactam-degradation ability.

Degradation of polynuclear aromatic hydrocarbons by two strains of Pseudomonas

ABSTRACT The goal of this investigation was to isolate competent polynuclear aromatic hydrocarbons degraders that can utilize polynuclear aromatic hydrocarbons of former industrial sites at McDoel Switchyard in Bloomington, Indiana. Using conventional enrichment method based on soil slurry, we isolated, screened and purified two bacterial species strains PB1 and PB2. Applying the ribotyping technique using the 16S rRNA gene analysis, the strains were assigned to the genus Pseudomonas (Pseudomonas plecoglossicida strain PB1 and Pseudomonas sp. PB2). Both isolates showed promising metabolic capacity on pyrene sprayed MS agar plates during the preliminary investigations. Using time course studies in the liquid cultures at calculated concentrations 123, 64, 97 and 94 ppm for naphthalene, chrysene, fluroanthene and pyrene, P. plecoglossicida strain PB1 and Pseudomonas sp. PB2 showed partial utilization of the polynuclear aromatic hydrocarbons. Naphthalene was degraded between 26% and 40%, chrysene 14% and 16%, fluroanthene 5% and 7%; pyrene 8% and 13% by P. plecoglossicida strain PB1 and Pseudomonas sp. PB2 respectively. Based on their growth profile, we developed a model R2 = 1 to predict the degradation rate of slow polynuclear aromatic hydrocarbon-degraders where all the necessary parameters are constant. From this investigation, we confirm that the former industrial site soil microbial communities may be explored for the biorestoration of the industrial site.

Analysis for the presence of determinants involved in the transport of mercury across bacterial membrane from polluted water bodies of India

Abstract Mercury, which is ubiquitous and recalcitrant to biodegradation processes, threatens human health by escaping to the environment via various natural and anthropogenic activities. Non-biodegradability of mercury pollutants has necessitated the development and implementation of economic alternatives with promising potential to remove metals from the environment. Enhancement of microbial based remediation strategies through genetic engineering approaches provides one such alternative with a promising future. In this study, bacterial isolates inhabiting polluted sites were screened for tolerance to varying concentrations of mercuric chloride. Following identification, several Pseudomonas and Klebsiella species were found to exhibit the highest tolerance to both organic and inorganic mercury. Screened bacterial isolates were examined for their genetic make-up in terms of the presence of genes (merP and merT) involved in the transport of mercury across the membrane either alone or in combination to deal with the toxic mercury. Gene sequence analysis revealed that the merP gene showed 86–99% homology, while the merT gene showed >98% homology with previously reported sequences. By exploring the genes involved in imparting metal resistance to bacteria, this study will serve to highlight the credentials that are particularly advantageous for their practical application to remediation of mercury from the environment.

Carbazole degradation in the soil microcosm by tropical bacterial strains

In a previous study, three bacterial strains isolated from tropical hydrocarbon-contaminated soils and phylogenetically identified as Achromobacter sp. strain SL1, Pseudomonas sp. strain SL4 and Microbacterium esteraromaticum strain SL6 displayed angular dioxygenation and mineralization of carbazole in batch cultures. In this study, the ability of these isolates to survive and enhance carbazole degradation in soil were tested in field-moist microcosms. Strain SL4 had the highest survival rate (1.8 x 107 cfu/g) after 30 days of incubation in sterilized soil, while there was a decrease in population density in native (unsterilized) soil when compared with the initial population. Gas chromatographic analysis after 30 days of incubation showed that in sterilized soil amended with carbazole (100 mg/kg), 66.96, 82.15 and 68.54% were degraded by strains SL1, SL4 and SL6, respectively, with rates of degradation of 0.093, 0.114 and 0.095 mg kg−1 h−1. The combination of the three isolates as inoculum in sterilized soil degraded 87.13% carbazole at a rate of 0.121 mg kg−1 h−1. In native soil amended with carbazole (100 mg/kg), 91.64, 87.29 and 89.13% were degraded by strains SL1, SL4 and SL6 after 30 days of incubation, with rates of degradation of 0.127, 0.121 and 0.124 mg kg−1 h−1, respectively. This study successfully established the survivability (> 106 cfu/g detected after 30 days) and carbazole-degrading ability of these bacterial strains in soil, and highlights the potential of these isolates as seed for the bioremediation of carbazole-impacted environments.

Indole acetic acid production by fluorescent Pseudomonas spp. from the rhizosphere of Plectranthus amboinicus (Lour.) Spreng. and their variation in extragenic repetitive DNA sequences.

Fluorescent Pseudomonas (FP) is a heterogenous group of growth promoting rhizobacteria that regulate plant growth by releasing secondary metabolic compounds viz., indole acetic acid (IAA), siderophores, ammonia and hydrogen cyanide. In the present study, IAA producing FPs from the rhizosphere of Plectranthus amboinicus were characterized morphologically, biochemically and at the molecular level. Molecular identification of the isolates were carried out using Pseudomonas specific primers. The effect of varying time (24, 48, 72 and 96 h), Trp concentrations (100, 200, 300, 400 and 500 µg.ml-1), temperature (10, 26, 37 and 50±2 °C) and pH (6, 7 and 8) on IAA production by 10 best isolates were studied. Results showed higher IAA production at 72 h incubation, at 300 µg.ml-1 Trp concentration, temperature 26±2 °C and pH 7. TLC with acidified ethyl acetate extract showed that the IAA produced has a similar Rf value to that of the standard IAA. Results of TLC were confirmed by HPLC analysis. Genetic diversity of the isolates was also studied using 40 RAPD and 4 Rep primers. Genetic diversity parameters such as dominance, Shannon index and Simpson index were calculated. Out of 40 RAPD primers tested, 9 (2 OP-D series and 7 OP-E series) were shortlisted for further analysis. Studies using RAPD, ERIC, BOX, REP and GTG5 primers revealed that isolates exhibit significant diversity in repetitive DNA sequences irrespective of the rhizosphere.

Production of biocontrol traits by banana field fluorescent Pseudomonads and comparison with chemical fungicide.

Pseudomonas aeruginosa isolated from banana field rhizosphere produced different antifungal metabolites like bactriocin, hydrogen cyanide and siderophore. Bacteriocinogenic, siderophoregenic, and HCN rich broth of isolate inhibited the growth of phytopathogen like Aspergilus niger, Aspergilus flavus, Fusarium oxysporum and Alternaria alternata. The isolate exhibited more antifungal activity and comparatively low MIC vis-a-vis commonly used copper based systemic chemical fungicide;bil cop.

Search for endophytic diazotrophs in barley seeds

Eight endophytic isolates assigned to Pseudomonas, Azospirillum, and Bacillus genera according to pheno-genotypic features were retrieved from barley seeds under selective pressure for nitrogen-fixers. Genetic relationships among related isolates were investigated through RAPD. Six isolates displayed nitrogen-fixing ability, while all could biosynthesize indolacetic acid in vitro and showed no antibiosis effects against Azospirillum brasilense Az39, a recognized PGPR.

The Effect of Temperature on Nitrate and Phosphate Uptake from Synthetic Wastewater by Selected Bacteria Species.

Aim: The aim of this study was to ascertain the effect of temperature on nutrient uptake ability of four bacterial species. Methodology: A total of four bacterial species (Klebsiella sp., Pseudomonas sp., Lysinibacillus sp. and Staphylococcus sp.) were used for the study. The media used for the investigation was synthetic wastewater. Four different temperatures (25ºC, 30ºC, 35ºC and 40ºC) were used for the investigation. The study was carried out under shake flasks conditions. Immediate after inoculation with the respective test bacterial species and every 24 h for a 96 h incubation time, aliquot wastewater samples were removed from the flasks for the estimation of total phosphate, nitrate, pH and growth rate, using standard procedures. Results: The results revealed phosphate and nitrate removal ranges of 10.84 % to 55.55 % and 90.67 % to 97.27 %, respectively in the presence of the Klebsiella sp. In the presence of the Pseudomonas sp, Lysinibacillus sp. and Staphylococcus sp., phosphate removals ranges of 0.36 % to 46.98 %, 11.89 % to 50.80 % and 2.74 % to 51.21 % were observed, respectively. For nitrate concentrations, removal levels that ranged from 2.19 % to 92.95 %, 0.97 % to 23.12 % and 7.56 % to 91.66 % were observed in the presence of Pseudomonas sp, Lysinibacillu ssp. and Staphylococcus sp., respectively. All the test bacterial species showed some measure of efficiency in phosphate removal. For nitrate removal, the Lysinibacillus sp. did not exhibit remarkable nitrate removal ability at any of the temperatures. In addition, the optimum temperatures for phosphate removals were observed to be 30ºC to 40ºC for the Klebsiella sp. and Pseudomonas sp; and 30ºC to 35ºC for the Lysinibacillus sp. and Staphylococcus sp. For nitrate removal, optimum temperatures for removal were observed to be 25ºC to 40ºC, for the Klebsiella sp and 25ºC to 35ºC, for the Pseudomonas sp. and Staphylococcus sp. Conclusion: The study was able to reveal the optimum temperatures for phosphate and nitrate uptake in synthetic wastewater by the test bacterial species.

Colonization and plant growth promoting characterization of endophytic Pseudomonas chlororaphis strain Zong1 isolated from Sophora alopecuroides root nodules

The endophytic strain Zong1 isolated from root nodules of the legume Sophora alopecuroides was characterized by conducting physiological and biochemical tests employing gfp-marking, observing their plant growth promoting characteristics (PGPC) and detecting plant growth parameters of inoculation assays under greenhouse conditions. Results showed that strain Zong1 had an effective growth at 28 ºC after placed at 4-60 ºC for 15 min, had a wide range pH tolerance of 6.0-11.0 and salt tolerance up to 5% of NaCl. Zong1 was resistant to the following antibiotics (µg/mL): Phosphonomycin (100), Penicillin (100) and Ampicillin (100). It could grow in the medium supplemented with 1.2 mmol/L Cu, 0.1% (w/v) methylene blue and 0.1-0.2% (w/v) methyl red, respectively. Zong1 is closely related to Pseudomonas chlororaphis based on analysis the sequence of 16S rRNA gene. Its expression of the gfp gene indicated that strain Zong1 may colonize in root or root nodules and verified by microscopic observation. Furthermore, co-inoculation with Zong1 and SQ1 (Mesorhizobium sp.) showed significant effects compared to single inoculation for the following PGPC parameters: siderophore production, phosphate solubilization, organic acid production, IAA production and antifungal activity in vitro. These results suggest strains P. chlororaphi Zong1 and Mesorhizobium sp. SQ1 have better synergistic or addictive effect. It was noteworthy that each growth index of co-inoculated Zong1+SQ1 in growth assays under greenhouse conditions is higher than those of single inoculation, and showed a significant difference (p < 0.05) when compared to a negative control. Therefore, as an endophyte P. chlororaphis Zong1 may play important roles as a potential plantgrowth promoting agent.

Biological control of potato black scurf by rhizosphere associated bacteria

The present work was carried out to study the potential of plant rhizosphere associated bacteria for the biocontrol of potato black scurf disease caused by Rhizoctonia solani Khun AG-3. A total of twenty-eight bacteria isolated from diseased and healthy potato plants grown in the soil of Naran and Faisalabad, Pakistan were evaluated for their antagonistic potential. Nine bacterial strains were found to be antagonistic in vitro, reduced the fungal growth and caused the lysis of sclerotia of R. solani in dual culture assay as well as in extracellular metabolite efficacy test. The selected antagonistic strains were further tested for the production and efficacy of volatile and diffusible antibiotics, lytic enzymes and siderophores against R. solani. Selected antagonistic bacteria were also characterized for growth promoting attributes i.e., phosphate solubilization, nitrogen fixation and indole acetic acid production. Biocontrol efficacy and percent yield increase by these antagonists was estimated in greenhouse experiment. Statistical analysis showed that two Pseudomonas spp. StT2 and StS3 were the most effective with 65.1 and 73.9 percent biocontrol efficacy, as well as 87.3 and 98.3 percent yield increase, respectively. Potential antagonistic bacterial strain StS3 showed maximum homology to Pseudomonas sp. as determined by 16S rRNA gene sequencing. These results suggest that bacterial isolates StS3 and StT2 have excellent potential to be used as effective biocontrol agents promoting plant growth with reduced disease incidence.

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, molecular characterization and growth-promotion activities of a cold tolerant bacterium Pseudomonas sp. NARs9 (MTCC9002) from the Indian Himalayas

A bacterium that grows and expresses plant growth promotion traits at 4°C was isolated from the rhizospheric soil of Amaranth, cultivated at a high altitude location in the North Western Indian Himalayas. The isolate was Gram negative and the cells appeared as rods (2.91 x 0.71 μm in size). It grew at temperatures ranging from 4 to 30°C, with a growth optimum at 28°C. It exhibited tolerance to a wide pH range (5-10; optimum 8.0) and salt concentrations up to 6 percent (wt/vol). Although it was sensitive to Rifampicin (R 20 μg mi-1), Gentamicin (G 3 μg mi-1), and Streptomycin (S 5 μg mi-1), it showed resistance to higher concentrations of Ampicillin (A 500 μg mi-1), Penicillin (P 300 μg mi-1), Polymixin B sulphate (Pb 100 μg mi-1) and Chloramphenicol (C 200 μg mi-1). The 16S rRNA sequence analysis revealed maximum identity with Pseudomonas lurida. The bacterium produced indole Acetic Acid (IAA) and solubilizes phosphate at 4, 15 and 28°C. It also retained its ability to produce rhamnolipids and siderophores at 15°C. Seed bacterization with the isolate enhanced the germination, shoot and root lengths of thirty-day-old wheat seedlings by 19.2, 30.0 & 22.9 percent respectively, as compared to the un-inoculated controls.

Toxicity assessment and microbial degradation of azo dyes.

Toxic effluents containing azo dyes are discharged from various industries and they adversely affect water resources, soil fertility, aquatic organisms and ecosystem integrity. They pose toxicity (lethal effect, genotoxicity, mutagenicity and carcinogenicity) to aquatic organisms (fish, algae, bacteria, etc.) as well as animals. They are not readily degradable under natural conditions and are typically not removed from waste water by conventional waste water treatment systems. Benzidine based dyes have long been recognized as a human urinary bladder carcinogen and tumorigenic in a variety of laboratory animals. Several microorganisms have been found to decolourize, transform and even to completely mineralize azo dyes. A mixed culture of two Pseudomonas strains efficiently degraded mixture of 3-chlorobenzoate (3-CBA) and phenol/cresols. Azoreductases of different microorganisms are useful for the development of biodegradation systems as they catalyze reductive cleavage of azo groups (-N=N-) under mild conditions. In this review, toxic impacts of dyeing factory effluents on plants, fishes, and environment, and plausible bioremediation strategies for removal of azo dyes have been discussed.

Degradation of microcystins by adsorbed bacteria on a granular active carbon (GAC) filter during the water treatment process.

The degradation of microcystin by adsorbed bacteria on GAC (granular active carbon) filter from a water treatment facility was investigated. Dominant bacteria isolated from GAC were indigenous microorganisms, Psuedomonas sp. and Flavobacterium sp. The direct exposure of dominant GAC bacteria to microcystins resulted in a significant reduction of microcystin levels in both shaking and static conditions (t-test; p < 0.01). In bacteria-treatments, the half-life of microcystin was 2.6-3.5 days in both conditions. Based on this result, approximately 9-10 days would be estimated for 90% or up to 18-21 days of 99% of toxin to be degraded. This biological degradation by the GAC bacteria in combination with existing purification systems has potential to increase the efficiency of water purification.

Growth of Brassica juncea under chromium stress: influence of siderophores and indole 3 acetic acid producing rhizosphere bacteria.

Plant growth promoting rhizobacterial (PGPR) strains A3 and S32 have been shown to promote the growth of Brassica juncea under chromium stress which has been related to the microbial production of siderophores and indole 3 acetic acid (IAA). The aim of the present study is to evaluate the importance of siderophores and IAA producing PGPR on the growth of Brassica juncea under chromium stress. The production of IAA and siderophores were observed in the strains A3 and S32, respectively. Both PGPR strains promote the growth of Brassica juncea under chromium stress. The maximum growth was observed in plants inoculated with siderophores producing strain 32. Both the bacterial inoculum did not influence the uptake of chromium by plants. The present observation showed that PGPR isolates A3 and S32 are capable of protecting the plants against the inhibitory effects of chromium by producing the siderophores and IAA.

Biosorption of heavy metals from waste water using Pseudomonas sp

Biosorption experiments for Cr(VI), Cu(II), Cd(II) and Ni(II) were investigated in this study using nonliving biomass of different Pseudomonas species. The applicability of the Langmuir and Freundlich models for the different biosorbent was tested. The coefficient of determination (R²) of both models were mostly greater than 0.9. In case of Ni(II) and Cu(II), their coefficients were found to be close to one. This indicates that both models adequately describe the experimental data of the biosorption of these metals. The maximum adsorption capacity was found to be the highest for Ni followed by Cd(II), Cu(II) and Cr(VI). Whereas the Freundlich constant k in case of Cd(II) was found to be greater than the other metals. Maximum Cr(VI) removal reached around 38 percent and its removal increased with the increase of Cr(VI) influent. Cu(II) removal was at its maximum value in presence of Cr(VI) as a binary metal, which reached 93 percent of its influent concentration. Concerning to Cd(II) and Ni(II) similar removal ratios were obtained, since it was ranged between 35 to 88 percent and their maximum removal were obtained in the case of individual Cd(II) and Ni(II).

Production of glycolipids containing biosurfactant by Pseudomonas species.

Microorganisms, that degrade hydrocarbon were isolated and screened for their biosurfactant activity. A total of 68 strains were isolated and tested for their glycolipid activity of which 4 isolates showed good glycolipid activity. Isolate K10 gave the maximum biosurfactant production in medium A (containing kerosene as a sole carbon source) as compared to medium B (containing glucose as a sole carbon source). Characterization of isolate K10 showed that it belongs to Pseudomonas species.

Sistemas de resistencia a metales en pseudomonas / Systems of resistence to metals in pseudomonas

Varios sistemas genéticos que confieren resistencia a metales pesados, codificados en el cromosoma o en plásmidos, han sido estudiados en bacterias del género pseudomonas y en microorganismos relacionados. Algunos de estos sistemas de tolerancia se conocen ahora a nivel molecular mientras que otros mecanismos no se han analizado aún con detalle. Entre los primeros se encuentran los genes que determinan la resistencia a los cationes derivados de mercurio, cadmio y cobre y los aniones de arsénico y cromo. Excepto para el mercurio, que involucra una transformación redox, las estrategias de resistencia más comunes se basan en la expulsión de los iones tóxicos del citoplasma bacteriano