Establishment and impact of Pseudomonas fluorescens genetically modified for lactose utilization and kanamycin resistance in the rhizosphere of pea

The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell Publishing DOI : 10.1046/j.1365-2672.1998.00321.xThe impact of a Pseudomonas fluorescens strain, genetically modified for kanamycin resistance and lactose utilisation (the GMM), could be enhanced by soil amendment with lactose and kanamycin. Lactose addition decreased the shoot to root ratio of pea, and both soil amendments increased the populations of total culturable bacteria and the inoculated GMM. Only kanamycin perturbed the bacterial community structure, causing a shift towards slower growing organisms. The community structure with the GMM inocula in the presence of kanamycin showed the only impact of the GMM compared to the wild type inocula. The shift towards K strategy (slower growing organisms), found in the other kanamycin-amended treatments, was reduced with the GMM inoculation. Lactose amendment increased the acid and alkaline phosphatase, the phosphodiesterase activity and the carbon cycle enzyme activities, whereas the kanamycin addition only affected the alkaline phosphatase and phosphodiesterase activities. None of the soil enzyme activities were affected by the GMM under any of the soil amendments.Peer reviewe

Effects of Pseudomonas fluorescens F113 on Ecological Functions in the Pea Rhizosphere Are Dependent on pH

The original publication is available at www.springerlink.com . Copyright Springer DOI : 10.1007/s002489900147The aim of this microcosm study was to determine influence of the antibiotic 2,4 diacetylphloroglucinol (DAPG) on the effect of wild type and functionally modified Pseudomonas fluorescens F113 strains in a sandy loam soil of pH 5.4 planted with pea (Pisum sativum var Montana). The functional modification of strain F113 was a repressed production of DAPG, useful in plant disease control, creating the DAPG negative strain F113 G22 both were marked with a lacZY gene cassette. Lowering the soil pH to 4.4 significantly reduced the plant shoot and root weights and the root length, whereas, the bacterial inocula had no significant effect. However, both inocula significantly reduced the shoot/root ratio at pH 5.4 but this effect was not evident at the lowered or elevated (6.4) pH levels. The decrease in pH significantly increased the fungal and yeast colony forming units from the rhizosphere (root extract) but did not affect the total bacterial cfu’s. Inoculation with strain F113 in the pH 4.4 soil resulted in a significantly greater total bacterial population The fungal and yeast cfu’s were not significantly affected by the inocula under any of the pH’s studied Increasing the pH significantly increased the indigenous Pseudomonas population in comparison to the reduced pH treatment and significantly increased both the introduced and total Pseudomonas populations. The antibiotic producing strain significantly reduced the total bacterial population and the NAGase activity (related to fungal activity) at pH 6.4 where the inocula population was the greatest. Alkaline phosphatase, phosphodiesterase, aryl sulphatase, glucosidase, alkaline galactosidase and NAGase activities significantly increased with increasing in pH. The F113 inocula reduced the acid phosphatase activity at pH 5.4 and increased the acid galactosidase activity over all the pH treatments. The results presented illustrate the variation in impact with soil pH, with implications for variability in efficacy of Pseudomonas fluorescens biocontrol agents with soil pH.Peer reviewe

Effect of 2,4-Diacetylphloroglucinol Producing, Overproducing, and Nonproducing Pseudomonas fluorescens F113 in the Rhizosphere of Pea

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Functional impact of genetically modified micro-organisms on the soil ecosystem

Most attempts to monitor the effects of introductions of Genetically Modified Micro-organisms (GMMs) have centred on the enumeration of specific populations. However for a significant perturbation to be measured, changes of between 100% and 300% (0.3 and 0.5 on a log scale) are necessary for the impact to be significant. Standard population measurements, assessing the survival, dissemination and effect on total indigenous populations do not give an indication of the functioning of the ecosystem. There is very little literature regarding the functional impact of GMMs, for instance the effect upon nutrient cycling or functionally important groups of organisms. Through out this review a number of methods for the detection of perturbation in the rhizosphere/soil ecosystem are assessed. A range of non functional methods are summarised first, including molecular and non molecular genetic population diversity studies. Functional methodology, for example nutrient cycling, is then assessed for application as indicators of impact in the soil ecosystem and the significance of measuring functional impact is highlighted. These functional methods are classified into those relying upon the culturability of the target organisms and those that do not. Non culture methods discussed include biomass, respiration, nutrient cycling, mRNA studies and soil enzyme assays. Recently a range of soil enzyme assays have been used as alternatives to population measurements. The impact of a chromosomally marked Pseudomonas fluorescens (SBW25), on soil chitobiosidase, N-acetyl glucosaminidase, acid and alkaline phosphatases, phosphodiesterase, aryl sulphatase and urease were studied. Using these enzyme assays impacts of less than 20% could be detected. A series of interactions were observed which depended on whether a mixture of soil enzyme substrates were added to soil. Generally, microbial inoculation increased the enzyme activity of the biomass, but effects are likely to be 2 dependent upon the nature of the genetic modification. The environmental implications of these effects are discussed

Rhizosphere soil enzymes as indicators of perturbations caused by enzyme substrate addition and inoculation of a genetically modified strain of Pseudomonas fluorescens on wheat seed

Original article can be found at: http://www.sciencedirect.com/science/journal/00380717 Copyright Elsevier Ltd. DOI : 10.1016/S0038-0717(97)00061-8Comparative assays for determining chitobiosidase, N-acetyl glucosaminidase, acid phosphatase, alkaline phosphatase, phosphodiesterase, aryl 2 sulfatase and urease activities from small samples of soil were developed. The enzyme assays and ATP biomass assessments were used to monitor perturbations caused by the presence of Pseudomonas fluorescens in the rhizosphere of wheat. Microbial biomass as well as the measured enzyme activities decreased with depth, except for acid phosphatase activity which was similar at all depths. A combined substrate mix addition of urea, colloidal chitin and glycerophosphate significantly increased N-acetyl glucosaminidase, chitobiosidase, aryl sulfatase and urease activities but did not cause a significant difference in acid and alkaline phosphatase and phosphodiesterase activities. Inoculation of seeds with P. fluorescens resulted in significant increases in rhizosphere chitobiosidase and urease activities at 5-20 cm depth and a significant decrease in alkaline phosphatase activity. Inoculation with the bacterium in the presence of substrate mix gave opposing effects to those treatments without substrate mix addition: chitobiosidase, aryl sulfatase and urease activities were significantly lower and alkaline phosphatase was significantly higher at the 5-20cm depth interval with inoculation of bacteria. Biomass values for the combined bacteria and substrate mix treatment were significantly higher than the substrate mix alone treatment.Peer reviewe

Effect of cadmium contamination with sewage sludge and phosphate fertiliser amendments on soil enzyme activities, microbial structure and available cadmium

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Effect of biocontrol strains of Trichoderma on plant growth, Pythium ultimum populations, soil microbial communities and soil enzyme activities

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Survival and ecological fitness of Pseudomonas fluorescens genetically engineered with dual biocontrol mechanisms

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The application of waste minimisation to business management to improve environmental performance in the food and drink industry

The food and drink industry is one of the major sectors in the UK and makes a significant contribution to national and regional economies. The sector produces a large amount of waste compared to other industries and it faces increasing demands to improve resource efficiency and environmental performance through European legislation and policy and UK waste strategy. Waste minimisation is considered to be one of the best approaches for improving sustainability performance in industry, including for the food and drink industry, as it achieves environmental, economic and social benefits by reducing waste at source, achieving cost savings and creating new employment opportunities

Soil enzyme activities in the rhizosphere of field-grown sugar beet inoculated with the biocontrol agent Pseudomonas fluorescens F113

The original publication is available at www.springerlink.com . Copyright Springer DOI : 10.1007/s003740050397Pseudomonas fluorescens F113, which produces the antimicrobial compound 2,4-diacetylphloroglucinol is a prospective biocontrol agent. Soil enzyme activities were used to investigate the ecological impact of strain F113 in the rhizosphere of field-grown sugar beet. There were distinct trends in rhizosphere enzyme activities in relation to soil chemistry (studied by electro-ultrafiltration). The activities of enzymes from the phosphorus cycle (acid phosphatase, alkaline phosphatase and phosphodiesterase) and of arylsulphatase were negatively correlated with the amount of readily available P, whereas urease activity was positively correlated with the latter. Significant correlations between electro-ultrafiltration nutrient levels and enzyme activity in the rhizosphere were obtained, highlighting the usefulness of enzyme assays to document variations in soil nutrient cycling. Contrary to previous microcosm studies, which did not investigate plants grown to maturity, the biocontrol inoculant had no effect on enzyme activity or on soil chemistry in the rhizosphere. The results show the importance of homogenous soil microcosm systems, used in previous work, in risk assessment studies, where inherent soil variability is minimised, and where an effect of the pseudomonad on soil enzymology could be detected.Peer reviewe