Motility and Chemotaxis of Pseudomonas Syringae Subsp. Glycinea
Hattermann, Dennis Robert
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Permalink
https://hdl.handle.net/2142/70617
Description
Title
Motility and Chemotaxis of Pseudomonas Syringae Subsp. Glycinea
Author(s)
Hattermann, Dennis Robert
Issue Date
1988
Doctoral Committee Chair(s)
Ries, Stephen M.
Department of Study
Plant Pathology
Discipline
Plant Pathology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Microbiology
Agriculture, Plant Pathology
Abstract
Flagellar motility in Pseudomonas syringae subsp. glycinea (Psg), as determined by capillary assay, is best at sub-optimal growth temperatures (17-27 C) and inhibited at higher temperatures. Motility is optimal in the presence of 10$\sp{-5}$ M EDTA in potassium phosphate buffer at pH 6-7. Reduced motility occurs in the absence of EDTA but motility is sharply inhibited at high concentrations (10$\sp{-4}$ to 10$\sp{-1}$ M). Exogenous energy sources such as glycerol, sodium citrate, and asparagine stimulate motility of Psg in the presence of oxygen.
Chemotaxis of Psg toward 10$\sp{-2}$ M sodium citrate, as determined by capillary assay, is optimal in chemotaxis medium containing 10$\sp{-2}$ M potassium phosphate buffer (pH 6.5), 10$\sp{-5}$ M EDTA, 5 $\times$ 10$\sp{-3}$ M MgCl$\sb2$, 10$\sp{-2}$ M glycerol, and at an assay temperature of 15-25 C. Assays are most sensitive when using a low cell concentration (4 $\times$ 10$\sp5$ cfu/ml) and a long incubation time (60 min).
Psg is attracted to leaf extracts from both susceptible and resistant soybean cultivars and the organic acid fraction of leaf extract is more attractive than either the amino acid or neutral-basic fractions. None of the fractions were as attractive as unfractionated extract. Psg is attracted most strongly to several organic acids including malate, fumarate, succinate, cis-aconitate, and tartrate and less strongly to amino acids such as N-carbamyl-DL-aspartate, proline, and histidine and is not attracted to sugars. Malate is the most powerful attractant of Psg of all chemicals tested.
Malate inhibited chemotaxis of Psg toward fumarate, citrate, succinate, histidine, proline, and soybean leaf extract which suggest that they are all detected by a single chemoreceptor. However, these results are contradicted by the observation that proline failed to provide reciprocal inhibition of chemotaxis toward malate and leaf extract.
A nonmotile strain (Nm7), obtained by mutagenesis with ethylmethanesulfonate, and its motile revertant (Mr7) were as pathogenic as the wild type strain on susceptible soybean (Wells II) leaves. Externally applied inoculum (leaf dip) of Mr7 resulted in significantly more lesions on susceptible soybean leaves (water-soaked by vacuum infiltration) than Nm7 at a concentration of 4 $\times$ 10$\sp5$ colony forming units per milliliter. Chemotaxis does not appear to be involved in soybean leaf invasion by Psg but it is possible that the true role of chemotaxis was not detected due to sensitivity limitations of the assay.
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