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Divining Rods: Pseudomonas putida as a microbiosensor of fine-scale osmotic potentials in soil.
Herron, Patrick*,1, Gage, Daniel2, Cardon, Zoe1, 1 Department of Ecology and Evolutionary Biology, Storrs, CT2 Department of Molecular and Cell Biology, Storrs, CT
ABSTRACT- The physical distribution and availability of water in soil influences plant growth, the mineralization of organic matter, the diffusion of dissolved nutrients and microbial dynamics. Current tools commonly used to measure water availability in soil, such as psychrometers, tensiometers and time domain reflectometry, integrate water availability on a gross scale but do not provide information at microscopic scales where microbes are operating. We have inserted an osmotically controlled proU-GFP transcriptional fusion developed by Axtell and Beattie (Appl. Env. Microbiol. Vol. 68:9, pp 4604-4612. 2002) into the soil bacterium Pseudomonas putida KT2440. The resulting soil microbial biosensor produces green fluorescent protein (GFP) as a function of osmotic potential around the bacterium. GFP fluorescence from the microbiosensors can be detected in nonsterile soils nondestructively using epifluorescence microscopy, and thus provides fine scale information on an important determinant of water potential in the soil microbial environment. These microbiosensors promise to provide a novel portrait of dynamics of rhizosphere osmotic potential associated with root water uptake.
Key words: Pseudomonas putida, Water potential, Biosensor, Rhizosphere