Role of alginate lyase in cell detachment of Pseudomonas aeruginosa

Abstract

The exopolysaccharide alginate of Pseudomonas aeruginosa was shown to be important in determining the degree of cell detachment from an agar surface. Nonmucoid strain 8822 gave rise to 50-fold more sloughed cells than mucoid strains 8821 and 8830. Alginate anchors the bacteria to the agar surface, thereby influencing the extent of detachment. The role of the P. aeruginosa alginate lyase in the process of cell sloughing was investigated. Increased expression of the alginate lyase in mucoid strain 8830 led to alginate degradation and increased cell detachment. Similar effects were seen both when the alginate lyase was induced at the initial stage of cell inoculation and when it was induced at a later stage of growth. It appears that high-molecular-weight alginate polymers are required to efficiently retain the bacteria within the growth film. When expressed from a regulated promoter, the alginate lyase can induce enhanced sloughing of cells because of degradation of the alginate. This suggests a possible role for the lyase in the development of bacterial growth films.

Extracellular products as mediators of the formation and detachment of Pseudomonas fluorescens biofilms

“…Whilst several candidate exopolysaccharide lyase enzymes and biosurfactants have been previously identi¢ed and associated with microbial bio¢lms [6], their mode of regulation is unclear. Expression of such`release agents' has been suggested to be regulated through environmental triggers, possibly associated with growth rate and/or nutrient starvation and stringency [14].…”

“…In order to colonise new surfaces and to avoid population density mediated starvation of attached bacteria, cells must be able to detach, and disperse, from mature bio¢lms and recolonise virgin surfaces. Such processess involve active detachment through enzymic cleavage of matrix polymers [6], or changes in the physiology of the attached cells [7]. There are suggestions that such mechanisms of detachment may be associated with the division cycle of individual cells of both Gram-negative [8] and Gram-positive [9] bacteria.…”

Characterization of starvation‐induced dispersion in Pseudomonas putida biofilms

“…The involvement in biofilms of outer membrane components and exopolymers that hold the microbes together in distinct spatial structures, and also attach the biofilms to surfaces, implies that degradation or modulation of the interconnecting components is of importance when emigration or structural rearrangements are needed. In accordance, alginate lyases have been proposed to have a role in biofilm dissolution for P. aeruginosa , P. fluorescens and Pseudomonas syringae (Boyd and Chakrabarty, 1994;Allison et al ., 1998;Ott et al ., 2001). Furthermore, it has been documented that the transition from the aggregated to the planktonic state for the archaea Methanosarcina mazei occurs via the expression of an exocellular endo-polysaccharide hydrolase (Xun et al ., 1990).…”

Polysaccharide lyases

“…A role for the alginate lyase of Pseudomonas aeruginosa in some environments has recently been suggested by Boyd and Chakrabarty [13]. They proposed that growth and adhesion of the bacteria in biofilms was strongly promoted by alginates and the action of the lyases in degrading the polymer, enhanced the release of cells from the solid surfaces.…”