Polar accumulation of pyoverdin and exit from stationary phase.

Pyoverdin is a water-soluble metal-chelator synthesized by members of the genus and used for the acquisition of insoluble ferric iron. Although freely diffusible in aqueous environments, preferential dissemination of pyoverdin among adjacent cells, fine-tuning of intracellular siderophore concentrations, and fitness advantages to pyoverdin-producing versus nonproducing cells, indicate control of location and release. Here, using time-lapse fluorescence microscopy to track single cells in growing microcolonies of SBW25, we show accumulation of pyoverdin at cell poles.

A leader cell triggers end of lag phase in populations of .

The relationship between the number of cells colonizing a new environment and time for resumption of growth is a subject of long-standing interest. In microbiology this is known as the "inoculum effect." Its mechanistic basis is unclear with possible explanations ranging from the independent actions of individual cells, to collective actions of populations of cells.

Emergence of Exopolysaccharides Overproducers Is Linked to Environmental Spatial Structure via Redox State.

The formation of biofilm at the air-liquid interface of a still flask is related to the emergence of exopolysaccharides (EPS) overproducers. These mutants have the ability to remain near the surface, where oxygen is abundant. Yet, it is still unclear what role oxygen plays in cellular metabolism under this condition.

Causes and Biophysical Consequences of Cellulose Production by Pseudomonas fluorescens SBW25 at the Air-Liquid Interface.

Cellulose-overproducing wrinkly spreader mutants of SBW25 have been the focus of much investigation, but conditions promoting the production of cellulose in ancestral strain SBW25 and its effects and consequences have escaped in-depth investigation through lack of an phenotype. Here, using a custom-built device, we reveal that in static broth microcosms, ancestral SBW25 encounters environmental signals at the air-liquid interface that activate, via three diguanylate cyclase-encoding pathways (Wsp, Aws, and Mws), production of cellulose. Secretion of the polymer at the meniscus leads to modification of the environment and growth of numerous microcolonies that extend from the surface.

Asymmetric adhesion of rod-shaped bacteria controls microcolony morphogenesis.

Surface colonization underpins microbial ecology on terrestrial environments. Although factors that mediate bacteria-substrate adhesion have been extensively studied, their spatiotemporal dynamics during the establishment of microcolonies remains largely unexplored. Here, we use laser ablation and force microscopy to monitor single-cell adhesion during the course of microcolony formation.

An individual-based model for biofilm formation at liquid surfaces.

The bacterium Bacillus subtilis frequently forms biofilms at the interface between the culture medium and the air. We present a mathematical model that couples a description of bacteria as individual discrete objects to the standard advection-diffusion equations for the environment. The model takes into account two different bacterial phenotypes.