Self-similar colony morphogenesis by gram-negative rods as the experimental model of fractal growth by a cell population

Abstract

The ability to form a fractal colony was shown to be common among several species of the family Enterobacteriaceae. Bacterial spreading growth in a two-dimensional field of nutrient concentration was indicated to be important for this experimental self-similar morphogenesis. As a basic analogy, the diffusion-limited aggregation model was suggested. Fractal dimensions of colonies were mostly in the range of values from 1.7 to 1.8, similar to those of the two-dimensional diffusion-limited aggregation model. Bacterial characteristics and culture conditions inducing changes in fractal patterns and growth rates were identified. The contribution of the bacterial multicellular nature to fractal morphogenesis is discussed.

Membrane filter (pore size, 0.22–0.45 μm; thickness, 150 μm) passing-through activity ofPseudomonas aeruginosaand other bacterial species with indigenous infiltration ability

“…L. monocytogenes is a small Gram‐positive rod with flagellum‐dependent motility. The remarkable tissue invasiveness [6] and dendritic spreading behavior in solid agar substrate [7] of L. monocytogenes are consistent with the filter infiltration ability exhibited herein as prompt passing‐through activity of the bacteria (Table 2).…”

Swarming and complex pattern formation in Paenibacillus vortex studied by imaging and tracking cells

“…Bacillus mycoides is also able to create asymmetric patterns from growth of extended chains of non-motile but filamentous cells [ 19 ]. Non-motile strains of the Enterobacteriaceae can also form fractal patterns [ 21 ]. As with motile organisms, surfactants and extracellular polymers are often important in facilitating colony extension [ 19 , 21 ].…”

Rhamnolipid‐Dependent Spreading Growth of Pseudomonas aeruginosa on a High‐Agar Medium: Marked Enhancement under CO2‐Rich Anaerobic Conditions

“…Loosening of this containing force by surfactant has been observed in comparative studies of swarming behaviors of surfactant-producing and nonproducing S. marcescens and B. subtilis (20). The function of biosurfactant serrawettins in the S. marcescens colony expansion (although it took 2-3 weeks) (22) has been partly explained in a computer simulation by introducing surface tension parameter (19). It was also noteworthy that such activity of surfactants under anaerobic conditions was CO 2 -dependent and not observed with nine other gram-negative rods (e.g., Burkholderia cepacia, data not shown).…”