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GrainGenes Reference Report: MCE-41-290

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Reference	MCE-41-290
Title	Monitoring population size, activity, and distribution of gfp-luxAB-tagged Pseudomonas fluorescens SBW25 during colonization of wheat
Journal	Microbial Ecology
Year	2001
Volume	41
Pages	290-300
Author	Unge A Jansson J
Abstract	Summary: Increasingly, focus has been directed towards the use of microorganisms as biological control agents to combat fungal disease, as an alternative to chemical fungicides. Pseudomonas fluorescens SBW25 is one bacterial strain that has been demonstrated to promote plant growth by biocontrol of pathogenic fungi. To understand the mode of action of this bacterium, information regarding its localization and metabolic activity on plants is important. In this study, a gfp/luxAB-tagged derivative of P. fluorescens SBW25, expressing the green fluorescent protein (GFP) and bacterial luciferase, was monitored during colonization of wheat starting from seed inoculation. Since bacterial luciferase is dependent on cellular energy reserves for phenotypic expression, metabolically active cells were detected using this marker. In contrast, the stable GFP fluorescence phenotype was used to detect the cells independently of their metabolic status. The combination of these two markers enabled P. fluorescens SBW25 cells to be monitored on wheat plants to determine their specific location and metabolic activity. Studies on homogenized wheat plant parts demonstrated that the seed was the preferred location of P. fluorescens SBW25 during the 65-day time period studied, but the leaves and roots were also colonized. Interestingly, the bacteria were also found to be metabolically active on all plant parts examined. In situ localization of P. fluorescens SBW25 using a combination of different microscopic techniques confirmed the preference for the cells to colonize specific regions of the seed. We speculate that the colonization pattern of P. fluorescens SBW25 can be linked to the mechanism of protection of plants from fungal infection
Keyword	[ Hide all but 1 of 51 ] bacteria bacterial biocontrol biological control biological control agents cell colonization disease ecology energy fluorescence fluorescens fungal fungal infection fungi fungicides gene transfer gfp green green fluorescent protein growth in situ infection inoculation its localization luciferase marker mechanism metabolic activity microorganisms mode of action monitoring pathogen pattern phenotype phytosphere population protection protein pseudomonas pseudomonas fluorescens region rhizosphere root seed seed inoculation strain sugar beet survival wheat plants

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