Spatio-temporal patterns generated by Salmonella typhimurium

Abstract

We present experimental results on the bacterium Salmonella typhimurium which show that cells of chemotactic strains aggregate in response to gradients of amino acids, attractants that they themselves excrete. Depending on the conditions under which cells are cultured, they form periodic arrays of continuous or perforated rings, which arise sequentially within a spreading bacterial lawn. Based on these experiments, we develop a biologically realistic cell-chemotaxis model to describe the self-organization of bacteria. Numerical and analytical investigations of the model mechanism show how the two types of observed geometric patterns can be generated by the interaction of the cells with chemoattractant they produce.

A user’s guide to PDE models for chemotaxis

“…A number of models have been developed based on systems of equations similar to (1) that successfully capture many key features of the lifecycle [38,44]. Understanding bacterial pattern formation has also benefited from modelling: certain bacteria, including E. coli and S. typhimurium, can be induced to form a variety of spatial patterns when provided a suitable environment [11,12,108]. Mathematical models indicate a chemotactic process in which cells produce an auto-attractant may underlie this patterning ( [101,108], see also [68]).…”

“…Understanding bacterial pattern formation has also benefited from modelling: certain bacteria, including E. coli and S. typhimurium, can be induced to form a variety of spatial patterns when provided a suitable environment [11,12,108]. Mathematical models indicate a chemotactic process in which cells produce an auto-attractant may underlie this patterning ( [101,108], see also [68]). Models based on the Keller-Segel equations have also been developed to understand whether chemotaxis may underpin embryonic pattern forming processes, such as the formation and dynamics of the primitive streak (an early embryonic structure that co-ordinates tissue movements) [81], pigmentation patterning in snakes [69] and fish [83] and cell colonisation and neural crest migration [54].…”

“…The inclusion of cell proliferation and cell death, however, becomes natural in systems when patterning through movement is occurring on a similar or slower timescale than that due to growth. There are many biological situations where this is likely to be the case, for example bacterial pattern formation [101,108] or endothelial cell movement and growth in response to VEGF during angiogenesis [17]. As was the case for defining appropriate signal kinetics, the functional representation of cell growth/death will vary according to the biological system under consideration.…”

The interaction of thin-film flow, bacterial swarming and cell differentiation in colonies of Serratia liquefaciens

“…At the same time many papers investigate through experiments the precise nature and classi"cation of these patterns (Ohgiwari et al 1992;Shimada et al 1995;Nakahara et al 1996). On the other hand, the good agreement between experiments and continuum dynamic approaches of several papers (Chiu et al 1994;Shapiro 1995;Woodward et al 1995;Rauprich et al 1996;Esipov & Shapiro 1998) highlight the relevance of these approaches. The development of highly consistent theories for understanding the strategies adopted by the bacteria is of signi"cant interest.…”

Quantitative Effects of Medium Hardness and Nutrient Availability on the Swarming Motility of Serratia liquefaciens

“…Colonies either inhabit the water-filled channels within the agar matrix in very soft media or may sit upon the surface of hard media (especially on the surface of dried agar plates). Colonies that occupy the space within the agar matrix are known to produce regular patterns of dots and strips, the dynamics of which are mostly linked to chemotactic and diffusive mechanisms Woodward et al, 1995). On very hard Figure 1.…”