Potential Of Pseudomonas Research Articles

The genome of a steinernematid-associated Pseudomonas piscis bacterium encodes the biosynthesis of insect toxins.

Several species of soil-dwelling Steinernema nematodes are used in the biocontrol of crop pests, due to their natural capacity to kill diverse lepidopteran species. Although this insect-killing trait is known to be augmented by the nematodes' Xenorhabdus endosymbionts, the role of other steinernematid-associated bacterial genera in the nematode lifecycle remains unclear. This genomic study aimed to determine the potential of Pseudomonas piscis to contribute to the entomopathogenicity of its Steinernema host. Insect larvae were infected with three separate Steinernema cultures. From each of the three treatments, the prevalent bacteria in the haemocoel of cadavers, four days post-infection, were isolated. These three bacterial isolates were morphologically characterised. DNA was extracted from each of the three bacterial isolates and used for long-read genome sequencing and assembly. Assemblies were used to delineate species and identify genes that encode insect toxins, antimicrobials, and confer antibiotic resistance. We assembled three complete genomes. Through digital DNA-DNA hybridisation analyses, we ascertained that the haemocoels of insect cadavers previously infected with Steinernema sp. Kalro, Steinernema sp. 75, and Steinernema sp. 97 were dominated by Xenorhabdus griffiniae Kalro, Pseudomonas piscis 75, and X. griffiniae 97, respectively. X. griffiniae Kalro and X. griffiniae 97 formed a subspecies with other X. griffiniae symbionts of steinernematids from Kenya. P. piscis 75 phylogenetically clustered with pseudomonads that are characterised by high insecticidal activity. The P. piscis 75 genome encoded the production pathway of insect toxins such as orfamides and rhizoxins, antifungals such as pyrrolnitrin and pyoluteorin, and the broad-spectrum antimicrobial 2,4-diacetylphloroglucinol. The P. piscis 75 genome encoded resistance to over ten classes of antibiotics, including cationic lipopeptides. Steinernematid-associated P. piscis bacteria hence have the biosynthetic potential to contribute to nematode entomopathogenicity.

Potential of Pseudomonas and Trichoderma from the Brazilian Amazon as Biocontrol Agents against the Wheat Blast Disease

Blast is one of the most significant wheat diseases, causing high yield losses in susceptible varieties under favorable conditions in Latin America, Southeastern Asia and Eastern Africa. The disease is caused by the ascomycetous fungal pathogen Pyricularia oryzae Triticum lineage (PoTl). Chemical control with fungicides has been used as a management strategy; however, the effectiveness of the major classes of high-risk site-specific systemic fungicides has been reduced due to the widespread prevalence of resistance, especially in Brazil. Biological control is seen as a highly important and sustainable strategy to minimize the impact of yield losses associated with wheat blast in areas where fungicides are ineffective. In our study, we specifically aimed to determine the biological control potential of the three isolates of fluorescent Pseudomonas and three of Trichoderma as the antagonists of PoTl, both in in vitro and under greenhouse conditions. Additionally, we aimed to describe the ultrastructural interactions among the biocontrol agents and the pathogen in vitro by means of scanning electron microscopy (SEM). Fluorescent P. wayambapalatensis ‘Amana’ or Pseudomonas sp. nov. ‘Yara’, both from the P. putida group, and Trichoderma koningiopsis ‘Cachara’ significantly reduced PoTl in vitro mycelial growth and the blast disease severity on wheat plants. The SEM analyses revealed ultrastructural antagonistic mechanisms: biofilm formation, direct antagonism and mycoparasitism. Further research on the topic should include the development of stable formulations of the Pseudomonas- and Trichoderma-based biocontrol agents selected in our study for managing the wheat blast disease and the field tests of the biofungicide formulations obtained thereafter.

Lipoproteolytic capacity and potential of Pseudomonas spp. isolated from cold raw milk.

The objective of the work described in this research communication was to determine the lipoproteolytic capacity and potential of Pseudomonas spp. from the microbiota of refrigerated raw milk. The influence of temperature and bacterial population on these activities was also evaluated. Pseudomonas spp. (PS) counts (30 °C/48 h) were confirmed by PCR. Proteolytic (10% milk agar) and lipolytic capacities (PLC) (tributyrin agar) were evaluated (21 °C/72 h). Proteolytic (PP) and lipolytic potential (LP) were assessed by measuring the diameter of the halos and were categorized as low or high. A total of 91.3% PS possessed PLC. The PP of 64.16% isolates was high and was frequently observed in PS from milk samples with higher counts and lower temperatures. The LP of 70.52% isolates was low, and higher LP was associated with low microbiological counts and temperatures. Genetic studies evaluating Pseudomonas spp. strains in the milking environment and investigating the origin of these isolates could be useful to improve the quality and shelf life of dairy products.

Removal of Bisphenol-A from Aqueous Solutions by Pseudomonas aeruginosa in Batch Reactors: Effect of Carbon Source, Temperature and Concentrations

AbstractThis study was carried out to investigate the potential ofPseudomonas aeruginosafor the removal of bisphenol-A (BPA) from synthetic wastewater. To achieve this, BPA removal capability ofP. aeruginosawith respect to BPA concentration, and temperature were examined in batch reactors. Experiments were conducted in the presence/absence of glucose, as a carbon source. The first set of experiments consisted of evaluating the kinetic of removal of BPA at different concentrations (5, 10, 20, and 30 mg BPA/L) without glucose. In the second set of experiments, three different glucose concentrations (0.5, 1.0, and 2.0 glucose/L) with BPA concentrations were tested. After settlement of theP. aeruginosabiomass in the shakers, supernatants and control groups were filtered and analyzed for BPA using high performance liquid chromatography. In the biotic study, BPA removal rates were between 63 % and 100 %. All concentrations of BPA under 20 mg/L were completely degraded at 25 and 35 ºC at first step. However, 30 mgBPA/L was decreased to 8.56 mg/L byP. aeruginosaat first step at 25 ºC. At the second step, all concentrations of BPA were completely degraded by the cells at the presence of glucose. Hence, it can be summarized that bisphenol A can be used byP. aeruginosaas an external carbon source in the wastewater environments.

English

English

Potential of Pseudomonas and Bacillus Isolates as Biocontrol Agents Against Fusarium Wilt of Eggplant

ABSTRACTPlant growth-promoting rhizobacteria (PGPR) are beneficial bacteria found on plant roots that induce growth by a wide variety of mechanisms. Ten isolates of Pseudomonas and Bacillus were isolated from eggplant rhizosphere soil and evaluated for their volatile compound efficacy against mycelial growth of Fusarium oxysporum f. sp. melongenae (Fomg) and tested for their ability to colonize eggplant (Solanum melongena L.) roots in vitro. PGPR strains inhibited mycelial growth of the target pathogen and the percentage of inhibition varied from 38% to 72% by means of inhibitory activities. Pseudomanas aeruginosa (P07–1) and P. putida (P11–4) were determined to be successful colonizers in eggplant seedlings. Also, a pot experiment was conducted to assess the induced resistance to Fusarium wilt of eggplant by PGPR strains. Among the PGPR isolates, P. aeruginosa (P07–1), P. putida (P11–4), P. aeruginosa (85A-2), Bacillus amyloliquefaciens (76A-1) and B. cereus (B10a) significantly reduced Fusarium wilt disease incidence by up to 85%. However, their combination was not more effective in suppressing the disease than the application of those isolates alone. The induction of peroxidase (POX, EC 1.11.1.7) and polyphenol oxidase (PPO, EC 1.14.18.1) enzymes was found to be significantly higher in comparison with the control group. Similarly, the proline levels in eggplants showed an increasing trend with the above isolates. However, catalase (CAT, 1.11.1.6) activity was not found to significantly contribute to the induced resistance mechanism. This study revealed that the promising PGPR isolates could be potentially very useful for the biocontrol of Fomg via enhancing disease resistance in eggplant plants.

Pseudomonas aeruginosa Cystic Fibrosis Isolates from Individual Patients Demonstrate a Range of Levels of Lethality in Two Drosophila melanogaster Infection Models

Recently, two Drosophila melanogaster models of infection, fly feeding and fly nicking, have been developed that allow a determination of pathogenic potential of Pseudomonas aeruginosa isolates. In this study, control strains, isolates from burn wounds, and isolates from the sputa of cystic fibrosis (CF) patients were used to compare the two infection models to determine whether any of the isolates might be better adapted to either of the models. In addition, our goal was to determine the variability of isolates from individual CF patients. Three of four control strains (PAO1, PAK, and PA14) caused significant mortality in the flies in both models of infection. The remaining control strain, PA103, was lethal to flies in the nicking model but lacked significant lethality in the feeding model. The burn wound isolates had a high level of lethality in both models. Interestingly, the CF isolates had the largest diversity of lethality in both models of infection. The range of pathogenic potentials of the CF isolates occurred across a cohort of patients, both at the patient level and down to the level of individual sputum samples. The majority of all isolates had similar levels of lethality in both fly infection models. However, two CF isolates were significantly more lethal in the nicking model, and three CF isolates were significantly more lethal in the feeding model. In conclusion, the two Drosophila infection models were useful for the analysis of the diversity of pathogenic potentials of P. aeruginosa isolates.

Increased resistance toFusarium oxysporumf. sp.radicis-lycopersiciin tomato plants treated with the endophytic bacteriumPseudomonas fluorescensstrain 63-28

The potential ofPseudomonas fluorescensstrain 63-28 for inducing defence reactions in tomato plants inoculated with the vascular fungusFusarium oxysporumf.sp.radicis-lycopersiciwas studied by light and transmission electron microcopy, and further investigated by gold cytochemistry. In non-bacterized tomato plants the pathogen multiplied abundantly through much of the root tissues, causing severe damage including cell disorganization and cell wall alterations. Marked changes in the rate and extent ofFusariumcolonization were observed in bacterized plants. The intensity of colonization was appreciably reduced compared to that observed in control plants, and pathogen growth was restricted to the outer root tissues with preferential localization in the intercellular spaces. The accumulation of an electron-dense material in epidermal and outer cortical cells and the coating of most intercellular spaces with similar substances were among the most typical features of host reactions. Cytochemical labelling of chitin showed that disorganization ofFusariumhyphae colonizing bacterized roots correlated with chitin degradation. These observations provided indirect evidence for the production of plant chitinases. Another noticeable change occurring during pathogen ingress in the outer root cortex was the elaboration of callose-enriched wall appositions at sites of attempted fungal penetration. These appositions were slightly labelled by the gold-complexed β-glucosidase, whereas gold particles were mainly concentrated over the more opaque regions lining the host cell walls and at the periphery of the electron-dense deposits accumulating in the intercellular spaces. The present ultrastructural observations confirm thatP. fluorescensstrain 63-28 may function as an inducer of plant disease resistance.

A toxicological screen to determine in vitro survival and competition of environmentally applied pseudomonads with mouse fecal microbiota

Engineered bacterial strains have been developed for several environmental uses, including bioremediation and application as biopesticides. Previous in vivo work in this laboratory examined the colonization and competition potential of Pseudomonas spp., isolated from a commercial product for PCB degradation with the intestinal flora of CD-1 mice. In the present study, the same pseudomonads and two additional Escherichia coli strains were evaluated by an in vitro tier testing approach developed to screen environmentally relevant microorganisms for their ability to colonize the mammalian intestinal tract and compete with the normal intestinal tract flora. In the initial tier, the competitor strains were tested for their ability to survive in anaerobic pure culture. Next, they were cultured anaerobically in the presence of mouse fecal microbiota. Finally, serial transfers were performed to monitor the survival and competition potential of each strain with the fecal microbiota. All of the tested strains survived for 48 h in pure culture, and all survived for 24 h in culture with the mouse fecal microbiota. Escherichia coli strains survived serial transfer through five cultures, although in declining numbers. Environmental Pseudomonas spp. survived transfer through three cultures but were not detected after four transfers. No effects of the competitor strains on the fecal microbiota were found. This in vitro system eventually will be used with human fecal microbiota. The potential consequences of human exposure to environmentally released microorganisms can then be extrapolated by comparison of human in vitro results with rodent in vitro and in vivo results in a parallelogram approach.

Biosynthesis of Poly-β-Hydroxyalkanoates from Pentoses by Pseudomonas pseudoflava

The potential of Pseudomonas pseudoflava to produce poly-beta-hydroxyalkanoates (PHAs) from pentoses was studied. This organism was able to use a hydrolysate from the hemicellulosic fraction of poplar wood as a carbon and energy source for its growth. However, in batch cultures, growth was inhibited completely at hydrolysate concentrations higher than 30% (vol/vol). When P. pseudoflava was grown on the major sugars present in hemicelluloses in batch cultures, poly-beta-hydroxybutyric acid (PHB) accumulated when glucose, xylose, or arabinose was the sole carbon source, with the final PHB content varying from 17% (wt/wt) of the biomass dry weight on arabinose to 22% (wt/wt) of the biomass dry weight on glucose and xylose. Specific growth rates were 0.58 h on glucose, 0.13 h on xylose, and 0.10 h on arabinose, while the specific PHB production rates based on total biomass ranged from 0.02 g g h on arabinose to 0.11 g g h on glucose. PHB weight-average molecular weights were 640,000 on arabinose and 1,100,000 on glucose and xylose. The absolute amount of PHB in the cells decreased markedly when nitrogen limitation was relaxed by feeding ammonium sulfate at the end of the PHB accumulation stage of the arabinose and xylose fermentations. Copolymers of beta-hydroxybutyric and beta-hydroxyvaleric acids were produced when propionic acid was added to shake flasks containing 10 g of glucose liter. The beta-hydroxyvaleric acid monomer content attained a maximum of 45 mol% when the initial propionic acid concentration was 2 g liter.