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Review
, 181 (6), 1703-12

Surface Motility of Serratia Liquefaciens MG1

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Review

Surface Motility of Serratia Liquefaciens MG1

L Eberl et al. J Bacteriol.

Figures

FIG. 1
FIG. 1
Growth of an expanding swarm culture on 0.6% agar. (A) Top view. (B) Microscopic inspection of the swirling cells at the outer region of the expanding colony. Cells have been sampled from the part of the colony in the squares and examined by electron microscopy (EM1 to -3). The central part of the colony contains cells that entered stationary phase, as judged from their appearance as round, less-flagellated cells (EM1). In the middle of the colony, the vegetative (biomass-producing) cells exhibit the swim cell morphology (EM2), and finally at the border, the highly motile, flagellated, and elongated swarm cells (EM3) (24) are organized in rafts (C).
FIG. 2
FIG. 2
Summary of the two major sensory, regulatory systems (ovals) involved in swarm cell differentiation and surface motility. Inducing stimuli (lightning) point to their respective sensory system. The fat horizontal arrows indicate the pathways targeted by the regulatory systems. The rectangles summarize the biological processes the combined action of which leads to expansion of the colony.
FIG. 3
FIG. 3
Quorum sensing and control of biosurfactant synthesis in S. liquefaciens MG1. (A) The divergently arranged genes swrI and swrR encode an AHL synthase (LuxI homologue) and a putative regulatory LuxR homologue, SwrR, respectively. The arrowheads indicate the direction of transcription. BHL is freely diffusible over the bacterial membranes as indicated by the shaded arrow pointing up and down. FUR, one of the furanone compounds produced by D. pulchra. The signal molecule, BHL, is thought to bind to SwrR which in turn up-regulates transcription of the swrA gene (the position of the swrA promoter is indicated by the arrowhead with horizontal lines). The signal inhibitor, FUR, is thought to pass through the bacterial membranes and compete with BHL for the binding site present on SwrR. SwrA encodes a peptide synthetase, SwrA, which catalyzes production of the surfactant serrawettin W2. It is not known whether passage of W2 through the bacterial membranes is passive or mediated by a transport system. (B) Side views of cultures by the drop-collapsing test (54). Small volumes of bacterial cultures were placed on the lid of a petri dish. wt, wild type; swrI, the swrI mutant; +BHL, the strain was grown in the presence of 200 nM BHL. (C) Swarming motility of the S. liquefaciens MG1 swrI swrA double mutant on medium supplemented with serrawettin W2 and drop-collapsing test (54) of water supplemented with serrawettin W2 at the concentrations (in micrograms per milliliter) indicated at the bottom of the panel.
FIG. 4
FIG. 4
Swarm colonies consisting of two strains. (A) Top view of a mixed culture of the S. liquefaciens MG1 flhD strain and the swrI mutant. The strains were applied at the dark spot in a 50:50 ratio. (B and C) Detection of GFP-tagged flhD cells by means of epifluorescence microscopy in the more-central part (B) and in the outer swirling layer of the colony (C). (D) Detection of swrI cells harboring a LuxR-based AHL monitor system (PluxI-gfp fusion) expressing GFP in response to the presence of extracellular AHL signal molecules by epifluorescence-light microscopy. (E) Top view of a mixed culture of P. aeruginosa PAO1 and S. liquefaciens MG1 swrI harboring the AHL monitor. (F) Microscopic inspection of the square in the outer part of the colony by epifluorescence-light microscopy.

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