Agglutination, Adherence, and Root Colonization by Fluorescent Pseudomonads

Abstract

Two fractions of agglutination activity towards fluorescent pseudomonads were detected in root washes of potato, tomato, wheat, and bean. High-molecular-mass (>106 Da) components in crude root washes agglutinated only particular saprophytic, fluorescent Pseudomonas isolates. Ion-exchange treatment of the crude root washes resulted in preparations of lower-molecular-mass (105 to 106 Da) fractions which agglutinated almost all Pseudomonas isolates examined. Also, components able to suppress agglutination reactions of pseudomonads with the lower-molecular-mass root components were detected in crude root washes of all crops studied. Pseudomonas isolates were differentially agglutinated by both types of root components. The involvement of these two types of root components in short-term adherence and in colonization was studied in potato, tomato, and grass, using Pseudomonas isolates from these crops. Short-term adherence of isolates to roots was independent of their agglutination with either type of root components. With agglutination-negative mutants, the high-molecular-mass components seemed to be involved in adherence of Pseudomonas putida Corvallis to roots of all crops studied. Short-term adherence to roots of four Pseudomonas isolates could be influenced by addition of both crude and ion-exchange-treated root washes, depending on their agglutination phenotype with these root wash preparations. Potato root colonization by 10 different isolates from this crop, over a period of 7 days, was not correlated with their agglutination phenotype. Aggmutants of P. putida Corvallis were not impaired in root colonization. It is concluded that the root agglutinins studied can be involved in short-term adherence of pseudomonads to roots but do not play a decisive role in their root colonization.

What makes Pseudomonas bacteria rhizosphere competent?

“…Although agglutinin plays a major role in the adherence and colonization abilities of P. putida strain Corvallis to bean and cucumber, the role of agglutinins is not general for all biocontrol strains. No agglutination-dependent adherence and root colonization could be demonstrated for 30 different Pseudomonas isolates on tomato, potato and grasses (Glandorf, 1992).…”

“…to plant roots include the outer membrane protein OprF of P. fluorescens OE 28.3 (de Mot et al ., 1992) and an agglutinin isolated from P. putida strain Corvallis that mediates agglutination of bacterial cells to a glycoprotein on the plant root (Anderson et al ., 1988). This bacterial protein encoded by the aggA locus was reported to be involved in the adherence to roots and in competitive colonization with the parental strain on the roots of bean (Anderson et al ., 1988), potato, tomato and grass (Glandorf, 1992). Although agglutinin plays a major role in the adherence and colonization abilities of P. putida strain Corvallis to bean and cucumber, the role of agglutinins is not general for all biocontrol strains.…”

Phenazines and their role in biocontrol by Pseudomonas bacteria

“…The outer membrane protein OprF of P. fluorescens OE28.3 is involved in attachment to wheat roots (DeMot et al ., 1991). A root‐surface glycoprotein agglutinin was shown to mediate agglutination of Pseudomonas putida isolate Corvallis (Buell & Anderson, 1993) but had no role in long‐term colonization (Glandorf et al ., 1994; Knudsen et al ., 1997).…”