Chemotactic attraction of Azospirillum lipoferum by wheat roots and characterization of some attractants

Abstract

Media from the in vitro association of wheat and Azospirillum lipoferum and from wheat plants alone proved to be chemotactically active. Medium from wheat plants showed a higher attraction than medium from the association. The main attractants were sucrose, glucose, and fructose. In mineral medium without any added sugars, and in association medium with sucrose supplied, and from wheat roots alone, a sucrose excretion and an active invertase were detected. By cleaving sucrose the chemotactic potential increased. Sucrose can not be metabolized by A. lipoferum, whereas glucose and fructose are. Utilization of glucose and fructose by the bacteria may explain why medium from the association wheat–Azospirillum was less chemotacticaly active than medium from wheat plants alone. Cleavage of sucrose has the additional effect of providing energy sources for bacterial growth and dinitrogen fixation.

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

“…bisporus, and/or production of metabolites, would create nutrient gradients to which chemotactic bacteria could respond. The ability of P. putida and P. tolaasii to move toward these nutrient sources may provide them with a distinct survival advantage (Heinrich & Hess, 1985;Ames & Bergman, 1981) and may also aid colonization of mycelium. The ability of the phenotypic variants to respond more rapidly to nutrient gradients may confer upon them an additional advantage and is consistent with the hypothesis that these forms are more suited to survival under nutrient-stressed conditions, where the ability to locate new and favourable niches is of prime importance (Rainey, 1989a;Kamoun & Kado, 1990).…”

“…This behavioural response provides bacteria with a means of locating nutrients and avoiding harmful environments (Chet & Mitchell, 1976). Chemotaxis plays an important role in microbial interactions and in colonization of the surfaces of plant roots (Currier & Strobel, 1977;Gitte et al, 1978;Heinrich & Hess, 1985;Bashan, 1986;Gafny et al, 1986;De Weger et al, 1987), seeds (Scher et al, 1985) and fungal propagules (Arora et al, 1983;Lim & Lockwood, 1988). Such colonization is often necessary before a bacterium can exert a physiological effect on its 'host'.…”

Flagella of a plant-growth-stimulating Pseudomonas fluorescens strain are required for colonization of potato roots

“…3). In this mutant strain, the impairment in biosynthesis of flagella may be in the basal body or hook structure, thus not supplying a functional basis for the polymerization of the flagellar subunits into a flagellum, comparable to the S. typhimurium mutants defective in hook-associated proteins (14 (5,12), root mucilage (19), and seed exudate (26). Furthermore, P. aeruginosa cells move through moist soil a distance of 2 cm in 24 h (11).…”

Improving micropropagation: effect ofAzospirillum brasilenseSp245 on acclimatization of rootstocks of fruit tree

“…Azospirillum spp. exhibited positive chemotaxis towards root exudates (Heinrich and Hess 1985) and colonized roots externally and internally by penetrating into the intercellular spaces so as to ensure long-term survival and persistent beneficial effects (Patriquin and Dobereiner 1978;Levanony and Bashan 1989;Vande Broek et al 1993;Russo et al 2005). During acclimatization phase, the inoculated Mr.S 2/5 plants showed a marked meristem apical activity when compared to the control, even though the shoot tips of control plantlets entered a dormant stage while Sp245-treated plant shoots demonstrated active apical growth for a significantly longer duration producing new nodes and leaves (Figure 3).…”