Dazzo, F. B. and Y. G. Yanni. 2013. CMEIAS: an improved computing technology for quantitative image analysis of root colonization by Rhizobacteria in situ at single-cell resolution. Pages 733-742 in F. de Bruijn, ed. Molecular microbial ecology of the rhizosphere, Volume 2. J Wiley & Sons, Hoboken, New Jersey.
This paper describes how computer-assisted microscopy can enhance studies on bacterial colonization of roots by defining ecologically significant events at single-cell resolution and the spatial scale at which they occur in situ. The acquired data are supported by rigorous statistical analyses, have high signal-to-noise outputs and provide deeper insights into rhizobacterial colonization behavior. Point pattern, plot-based quadrat-lattice, and geostatistical analyses are used to distinguish bacterial distributions that are completely random (Null hypothesis) versus nonrandom patterns that cannot be explained by chance. The latter involve positive, aggregated interactions or negative interactions resulting in self-avoiding colonization behavior. In the first of two experimental examples, image analyses of a scanning electron micrograph illustrate how the colonization pattern of a superior inoculant strain of Rhizobium leguminosarum bv. trifolii forms discontinuous biofilms on the rice root surface, represented by spatially discrete bacterial aggregates that influence local densities of neighboring cells over a radial separation distance of ∼12 µm, which encapsulates all 494 bacteria in that image. The second example investigates the spatial heterogeneity in intensity of bacterial gene expression activated by N-acylhomoserine lactone-mediated cell-to-cell communication during colonization of wheat roots by reporter strains of Pseudomonas putida. Both examples show how computer-assisted microscopy can provide ecologically important information when included in studies of rhizobacterial colonization of plant root surfaces.
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