Should we stay or should we go: mechanisms and ecological consequences for biofilm dispersal

Abstract

In most environments, bacteria reside primarily in biofilms, which are social consortia of cells that are embedded in an extracellular matrix and undergo developmental programmes resulting in a predictable biofilm 'life cycle'. Recent research on many different bacterial species has now shown that the final stage in this life cycle includes the production and release of differentiated dispersal cells. The formation of these cells and their eventual dispersal is initiated through diverse and remarkably sophisticated mechanisms, suggesting that there are strong evolutionary pressures for dispersal from an otherwise largely sessile biofilm. The evolutionary aspect of biofilm dispersal is now being explored through the integration of molecular microbiology with eukaryotic ecological and evolutionary theory, which provides a broad conceptual framework for the diversity of specific mechanisms underlying biofilm dispersal. Here, we review recent progress in this emerging field and suggest that the merging of detailed molecular mechanisms with ecological theory will significantly advance our understanding of biofilm biology and ecology.

Bacterial swimmers that infiltrate and take over the biofilm matrix

“…These cells spread, promoting active seeding and dispersal (10,21). In contrast, stealth swimmers were observed in mature biofilms and also in early stages of biofilm formation (Fig.…”

“…(8,9). However, motile cells in mature biofilms have thus far been described as arising from a late-stage differentiation event (e.g., within hollow voids of Pseudomonas aeruginosa mushroom-like structures) and being involved in dispersion of mature biofilms (10).…”

Extracellular matrix structure governs invasion resistance in bacterial biofilms

“…If nutrient sources persist, biofilms can grow into structures many orders of magnitude larger than individual cells. By contrast, if resources become depleted, bacteria can disperse back into the planktonic phase, presumably to encounter new locations with superior resource availability (Kaplan, 2010;Landini et al, 2010;McDougald et al, 2012). The ability of planktonic bacteria to adhere to naked surfaces and initiate biofilm formation has been studied extensively (Beachey, 1981;Palmer et al, 2007).…”

The role of quorum sensing signalling in EPS production and the assembly of a sludge community into aerobic granules

“…This is in contrast to their planktonic single species population counterparts commonly studied in laboratory conditions. The formation and dispersal of structured bacterial biofilms or aggregates occur in response to a range of environmental cues and signals, such as changes in nutrient concentrations, oxygen, temperature, as well as chemicals and predatory stresses (Bassler et al, 1993;Matz et al, 2004;McDougald et al, 2011;Mitri et al, 2011). In many cases, the signal transduction pathways, the associated changes in gene expression and the involvement of second messenger systems have also begun to be unravelled (Barraud et al, 2009;Petrova and Sauer, 2012).…”