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

Abstract

Pseudomonas fluorescens B52 produces substantial biofilms at the air/liquid/solid interface of glass coverslips clamped vertically and partly submerged in liquid medium at 21³C. Biofilm formation was maximal ca. 20^50 h after inoculation of the liquid medium and, as indicated by environmental scanning electron microscopy (ESEM), contained large numbers of bacterial cells that were embedded within an extensive exopolymeric matrix. Incubation beyond 50 h led to reductions in biofilm which ESEM related primarily to losses of exopolymer. Both biofilm formation and the subsequent decline in exopolymer deposition was more rapid, and occurred to greater extents, when supernatants from two-day old cultures of B52 were used as the initial growth media. The addition of N-acyl-hexanoyl homoserine lactone to fresh growth medium had a similar effect upon biofilm formation as using spent culture medium. Homoserine lactones could not be demonstrated in spent culture supernatants by an Agrobacterium tumefaciens bioassay. An exopolysaccharide lyase was detected in spent culture media taken from dense biofilm cultures whose action was specifically directed towards biofilm exopolysaccharide. Results suggest that (i) cell-cell signals such as homoserine lactones are associated with the formation of P. fluorescens biofilms, (ii) the enzymic degradation of exopolymers has a specific role in the detachment of cells under starvation conditions, and (iii) whilst short chain (C T ) exogenous homoserines can trigger such responses in P. fluorescens, its own signal substance is likely to possess a longer ( s C V ) fatty acyl chain. z

Biofilm Dispersal: Mechanisms, Clinical Implications, and Potential Therapeutic Uses

“…S9 (Wrangstadh et al, 1989). In P. fluorescens, starvation induced an increase in exopolysaccharide lyase production and biofilm dispersal (Allison et al, 1998), whereas in P. aeruginosa, alginate lyase activity was maximally induced in rapidly growing cells (Ott et al, 2001). Again, both of these observations suggest that increased biofilm dispersal rates may occur under both favorable and unfavorable conditions.…”

Cellulose Expression in Pseudomonas fluorescens SBW25 and Other Environmental Pseudomonads

“…For example, the quorum signalling molecule, acyl-homoserine lactone (AHL), functions as a signal for the development of P. aeruginosa PA01 and Pseudomonas fluorescens B52 biofilms [36][37]. However, mathematical models based on O2 and nutrient transport (diffusion) limitation result in similar biofilm architecture (reviewed in [38]), suggesting biofilm development is equally sensitive to environmental conditions as it may be to geneticallydetermined regulation.…”

A Homologue of the 3-Oxoacyl-(Acyl Carrier Protein) Synthase III Gene Located in the Glycosylation Island of Pseudomonas syringae pv. tabaci Regulates Virulence Factors via N -Acyl Homoserine Lactone and Fatty Acid Synthesis

“…The flagellum-mediated swarming motility might be induced at this detachment process owing to the limited availability of nutrients, including iron, in the mature biofilm. Recent papers have suggested that each process of biofilm formation might be regulated by expression of quorum-sensing genes (1,9). These dynamic alternations in gene expression for biofilm formation might be regulated by the orf3 gene in relation to flagellum expression.…”