title: In situ quantitation of the spatial scale of calling distances and population density-independent N-acylhomoserine lactone-mediated communication by rhizobacteria colonized on plant roots.
abstract: We used computer-assisted microscopy at single cell resolution to quantify the in situ spatial scale of N-acylhomoserine lactone (AHL)-mediated cell-to-cell communication of Pseudomonas putida colonized on tomato and wheat root surfaces. The results of this in situ quantification study on close-to-natural surfaces challenge the conventional view of a quorum group requirement of high cell densities for this type of bacterial communication. In situ image analysis indicated that the effective 'calling distance' on root surfaces was most frequent at 4-5 microm, extended to 37 microm in the root tip/elongation zone and further out to 78 microm in the root hair zone. The spatial scale of these calling distances is very long-range in proportion to the size of individual bacteria. Geostatistical modeling analysis implicated the importance of AHL-gradients mediating effective communication between remote cells. We conclude that AHL-mediated cell-to-cell communication occurs not only within dense populations, but also in very small groups and over long ranges between individual bacteria, and therefore this cellular activity is more commonplace and effective than hitherto predicted. We propose that this cell-to-cell communication is governed more by the in situ spatial proximity of cells within AHL-gradients than the requirement for a quorum group of high population density.
authors.affiliation: Institut für Bodenökologie, Abteilung Rhizosphärenbiologie, GSF-Forschungszentrum für Umwelt and Gesundheit, Neuherberg/München, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Gantner
authors.forename: Michael
authors.initials: M
authors.lastname: Schmid
authors.forename: Christine
authors.initials: C
authors.lastname: Dürr
authors.forename: Regina
authors.initials: R
authors.lastname: Schuhegger
authors.forename: Anette
authors.initials: A
authors.lastname: Steidle
authors.forename: Peter
authors.initials: P
authors.lastname: Hutzler
authors.forename: Christian
authors.initials: C
authors.lastname: Langebartels
authors.forename: Leo
authors.initials: L
authors.lastname: Eberl
authors.forename: Anton
authors.initials: A
authors.lastname: Hartmann
authors.forename: Frank B
authors.initials: FB
authors.lastname: Dazzo
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000378:metabolism; D015169:Colony Count, Microbial; D017930:Genes, Reporter; D007091:Image Processing, Computer-Assisted; D018551:Solanum lycopersicum / Q000382:microbiology; D018613:Microscopy, Confocal / Q000379:methods; D008954:Models, Biological; D018517:Plant Roots / Q000382:microbiology*; D011549:Pseudomonas / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D014908:Triticum / Q000382:microbiology
chemical_list: C088386:homoserine lactone; D015107:4-Butyrolactone