Community biofilm-formation, stratification and productivity in serially-transferred microcosms

Abstract

The establishment of O2 gradients in liquid columns by bacterial metabolic activity produces a spatially-structured environment. This produces a high-O2 region at the top that represents an un-occupied niche which could be colonised by biofilm-competent strains. We have used this to develop an experimental model system using soil-wash inocula and a serial-transfer approach to investigate changes in community-based biofilm-formation and productivity. This involved ten transfers of mixed-community or biofilm-only samples over a total of 10–60 days incubation. In all final-transfer communities the ability to form biofilms was retained, though in longer incubations the build-up of toxic metabolites limited productivity. Measurements of microcosm productivity, biofilm-strength and attachment levels were used to assess community-aggregated traits which showed changes at both the community and individual-strain levels. Final-transfer communities were stratified with strains demonstrating a plastic phenotype when migrating between the high and low-O2 regions. The majority of community productivity came from the O2-depleted region rather than the top of the liquid column. This model system illustrates the complexity we expect to see in natural biofilm-forming communities. The connection between biofilms and the liquid column seen here has important implications for how these structures form and respond to selective pressure.

eDNA Inactivation and Biofilm Inhibition by the PolymericBiocide Polyhexamethylene Guanidine Hydrochloride (PHMG-Cl)

“…Biofilms are a form of bacterial colonization of the environment [ 44 , 45 , 46 , 47 ]. eDNA is an extracellular matrix polymer found in the biofilms of many important opportunists, such as Acinetobacter baumannii , Enterococcus faecalis , Helicobacter pylori , P. aeruginosa , and Staphylococcus spp.…”

eDNA, Amyloid Fibers and Membrane Vesicles Identified in Pseudomonas fluorescens SBW25 Biofilms

“…Earlier epifluorescent microscopy illustrated well the network of cellulose fibers seen in Viscous Mass and Wrinkly Spreader biofilms and encompassing large voids filled with bacteria [ 20 , 22 , 35 ]. Wild-type P. fluorescens SBW25 and Wrinkly Spreader mutant cells are capable of swimming motility and capable of aerotaxic migration that would allow them to colonize any part of the A–L interface biofilm [ 74 ], with fitness assays suggesting that the preferred Goldilocks’ zone for growth is at the top of the A–L interface [ 19 ] (CLSM suggests that the top-most layer of active cells is just below the exposed surface of the Wrinkly Spreader biofilm [ 52 ]). P. fluorescens SBW25 can utilize exogenous intermolecular agar networks and polyethylene glycol intermolecular friction to quickly colonize the A–L interface [ 74 ] suggesting that any viscous or viscoelastic matrix can be used as the basis for biofilm formation.…”

“…Wild-type P. fluorescens SBW25 and Wrinkly Spreader mutant cells are capable of swimming motility and capable of aerotaxic migration that would allow them to colonize any part of the A–L interface biofilm [ 74 ], with fitness assays suggesting that the preferred Goldilocks’ zone for growth is at the top of the A–L interface [ 19 ] (CLSM suggests that the top-most layer of active cells is just below the exposed surface of the Wrinkly Spreader biofilm [ 52 ]). P. fluorescens SBW25 can utilize exogenous intermolecular agar networks and polyethylene glycol intermolecular friction to quickly colonize the A–L interface [ 74 ] suggesting that any viscous or viscoelastic matrix can be used as the basis for biofilm formation. It is likely therefore that cellulose and eDNA network structures or scaffolds might be colonized by motile cells to produce extensions from the original biofilm or new initial biofilm formation on uncolonized surfaces.…”