The Role of Motility and Aerotaxis in the Selective Increase of Avirulent Bacteria in Still Broth Cultures of Pseudomonas solanacearum

Abstract

A difference in relative motility between virulent and avirulent Pseudomonas solanacearum was a possible factor in the shift from virulent to avirulent populations in still broth cultures. Virulent isolates grown on solid media or in tryptone yeast-extract glucose or glycerol broth for 24 to 48 h were mainly non-flagellated or non-motile, whereas avirulent isolates grown under the same conditions were usually flagellated and highly motile. Fimbriae were observed in electron photomicrographs of both types. A rapid preferential increase of avirulent bacteria occurred when mixtures were grown in still, but not in shaken, broth cultures; this relative increase was greatest close to the surface of the medium. Rapid aerotaxis of avirulent bacteria was demonstrated in mixtures of virulent and avirulent bacteria in a semisolid motility agar medium. Positive aerotaxis and high motility apparently favoured rapid increase of avirulent P. solanacearum when oxygen became limiting in broth media, in which virulent bacteria were not actively motile.

Phenotypic variation of Pseudomonas putida and P. tolaasii affects the chemotactic response to Agaricus bisporus mycelial exudate

“…Phenotypic variants of P . solanacearum (Kelman & Hruschka, 1973) and Xanthomonas campestris (Kamoun & Kado, 1990) are also reported to behave in this manner. The more rapid chemotactic response shown by the phenotypic variants is likely to be due in part to their faster swimming speed; however, other factors such as metabolic/respiration rate, surface properties and number and location of chemoreceptors may also be important.…”

Initiation of Biofilm Formation by Pseudomonas aeruginosa 57RP Correlates with Emergence of Hyperpiliated and Highly Adherent Phenotypic Variants Deficient in Swimming, Swarming, and Twitching Motilities

“…Very few examples of phase variation mechanisms regulating simultaneously multiple phenotypic determinants have been reported. Interestingly, in most cases, the phenotypic switch influences the tactic response (23,24). In the mushroom pathogen P. tolaasii, a spontaneous and reversible duplication within a two-component sensor regulator, causing a frameshift mutation, regulates many phenotypic traits, including attachment, colonial form, and chemotaxis (19).…”

Identification of a locus that regulates multiple functions in Pseudomonas solanacearum

“…Fallen Leaf Conf., p. 21, 1989; C. Allen, Y. Huang, and L. Sequeira, Mol. Plant-Microbe Interact., in press) and cellulase (9), lipopolysaccharide structure (5), piliation (18), synthesis of indoleacetic acid (16), and restoration of motility (10).…”