plant surface microbiology.pdf

27 Applications of Quantitative Microscopy in Plant Surface Microbiology 543
6.7 CMEIAS v. 3.0: Spatial Scale Analysis of in Situ Quorum Sensing by
Root-Colonizing Bacteria
In the fifth example, CMEIAS is being used to extract information that sheds
new light on the spatial scale at which cell-cell communication of quorum
sensing occurs in situ during bacterial colonization of roots. This work is
being done in a collaboration of the author with Prof. Anton Hartmann,
Stephan Gantner and Christine Duerr in Germany. Confocal fluorescence
images of roots are acquired to locate the positions of the red fluorescent protein
reporter strain of bacteria that produces and secretes the acyl homoserine
lactone quorum signal (source cells) and the green GFP-reporter strain of
bacteria that cannot produce these signal molecules, but is nevertheless activated
by them (sensor cells). The range of distances between each green sensor
cell and its nearest red source cell neighbor then becomes a measure of the
spatial scale at which the cell-to-cell communication of quorum-sensing signal
molecules occurs in situ during root colonization. Early indications are
that this spatial scale is close to the same range found for spatial dependence
in root colonization as described in Fig. 15 above. Figure 17 further illustrates
Fig. 17. CMEIAS/GS+
spatial geostatistical
analysis of in situ
quorum sensing
among neighboring
bacteria colonizing
the root surface. A
Dot map indicating
the location of bacteria
that provide the
source of the extracellular
quorum signal
molecule (N-acyl
homoserine lactone).
Scale bar 10 mm. B 2-
D interpolation kriging
map of the predicted
gradients of
the quorum sensing
molecule in situ on
the root surface based
on the localized cluster
indices of colonized
bacteria