Emerging morphologies in round bacterial colonies: comparing volumetric versus chemotactic expansion

Giverso, Chiara; Verani, Marco; Ciarletta, Pasquale

doi:10.1007/s10237-015-0714-9

Cited by 25 publications

(31 citation statements)

References 59 publications

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“…The bacterial population plays crucial roles in swarming by secreting osmolytes, to draw the fluid out of the agar (40), and surfactants, to reduce surface tension and ease the spreading of swarm fluid. The process is essentially a volumetric expansion (35). Although several models invoking reaction-diffusion (34,35,57), chemotaxis (33), or quorum sensing (31), are able to yield dendritic or fingering growth at the swarm front, results from the simple manipulation of physical factors presented in this report suggest that biologically specific molecular mechanisms, such as chemotaxis and quorum sensing, are not required for swarming.…”

Section: Possible Causes Of Dendritic Swarm Patternsmentioning

confidence: 78%

“…Examples include a reaction-diffusion model based on the idea that branched protrusions may be driven by opposing biochemical agents of competing drives (57), a model based on Marangoni flow (29,58), and a new analysis of branching instability assuming either volumetric or chemotactic expansion (34,35). In particular, Giverso et al (34,35) draw upon a strikingly similar physical phenomenon, classically known as viscous fingering (59,60), to suggest its relevance to the dendritic spread of bacterial swarm fronts. The ensuing discussion seeks to connect existing models with the fingerlike swarm patterns of P. aeruginosa, albeit at the qualitative level, with the aim of stimulating further study.…”

Section: Possible Causes Of Dendritic Swarm Patternsmentioning

confidence: 99%

“…However, this model does not provide a physical mechanism by which the dendritic front is initiated, although the model described resembles a reaction-diffusion process (57). Indeed, theoretical models based on the reaction-diffusion mechanism can yield dendritic growth both via a linear stability analysis and through computer simulations (34,35,57). However, these theoretical models have not been applied yet to the empirical findings on P. aeruginosa (33).…”

Section: Possible Causes Of Dendritic Swarm Patternsmentioning

confidence: 99%

“…These dendrites, or tendrils, are long, thin regions of colonization that emerge from the spot of inoculation or from other dendrites (25)(26)(27). Although there have been numerous studies that characterize the swarm morphology of P. aeruginosa strains under varied physicochemical conditions (25,26,(28)(29)(30)(31)(32)(33), the exact mechanism of dendritic growth remains an open question despite several models proposed (25,28,29,34,35). In addition, although P. aeruginosa does not swarm as a monolayer (36), the cells close to the agar surface can use type IV pili to move via twitching motility, in which the bacteria extend and retract their pili on surfaces, especially on harder substrate (~1% agar) (37).…”

Section: Introductionmentioning

confidence: 99%

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Influence of Physical Effects on the Swarming Motility of Pseudomonas aeruginosa

Yang

Tang

et al. 2017

Biophysical Journal

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Many species of bacteria can spread over a moist surface via a particular form of collective motion known as "surface swarming". This form of motility is typically studied by inoculating bacteria on a gel formed by 0.4-1.5% agar, which contains essential nutrients for their growth and proliferation. Using Pseudomonas aeruginosa and its pili-less mutant, ΔPilA, we investigate physical factors that either facilitate or restrict the swarming motility, measured by the rate of increase in area covered by a spreading bacterial colony, i.e., a swarm. The wild-type colony spreads over the agar surface in highly branched structures. The pili-less mutant fills up the area more fully as it spreads, but it also produces numerous and fragmented branches, or tendrils, at the swarm front. Whereas additional surfactants enhance swarming, increasing the agar percentage, adding extra salt or sugar or incorporating viscous agents in the agar matrix all decrease swarming, supporting the conclusion that swarming motility is restricted by the surface tension at the swarm front and swarm growth is limited by the rate of water supply from within the agar gel. The physical basis elaborated through this study provides a useful framework for understanding the swarming behavior of numerous species of bacteria.

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Section: Possible Causes Of Dendritic Swarm Patternsmentioning

confidence: 78%

Section: Possible Causes Of Dendritic Swarm Patternsmentioning

confidence: 99%

Section: Possible Causes Of Dendritic Swarm Patternsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Influence of Physical Effects on the Swarming Motility of Pseudomonas aeruginosa

Yang

Tang

et al. 2017

Biophysical Journal

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“…Moreover, the importance of such branching increases monotonically along the experimental time evolution. Such a behavior is analogous to the result of detailed continuum models of bacterial colony growth put forward in [35,36], which predict unconditional instability of the colony front to perturbations for a variety of relaxation mechanisms that include both, chemotactic and volumetric expansions. In application of the analysis in [35,36] to our data, Fig.…”

Section: B Geometrical Properties: Local Roughness and Radial Correlmentioning

confidence: 64%

Nonuniversality of front fluctuations for compact colonies of nonmotile bacteria

et al. 2018

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The front of a compact bacterial colony growing on a Petri dish is a paradigmatic instance of non-equilibrium fluctuations in the celebrated Eden, or Kardar-Parisi-Zhang (KPZ), universality class. While in many experiments the scaling exponents crucially differ from the expected KPZ values, the source of this disagreement has remained poorly understood. We have performed growth experiments with B. subtilis 168 and E. coli ATCC 25922 under conditions leading to compact colonies in the classically alleged Eden regime, where individual motility is suppressed. Non-KPZ scaling is indeed observed for all accessible times, KPZ asymptotics being ruled out for our experiments due to the monotonic increase of front branching with time. Simulations of an effective model suggest the occurrence of transient nonuniversal scaling due to diffusive morphological instabilities, agreeing with expectations from detailed models of the relevant biological reaction-diffusion processes.

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Morphological Stability for in silico Models of Avascular Tumors

Blom,

Engblom

2024

Bull Math Biol

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The landscape of computational modeling in cancer systems biology is diverse, offering a spectrum of models and frameworks, each with its own trade-offs and advantages. Ideally, models are meant to be useful in refining hypotheses, to sharpen experimental procedures and, in the longer run, even for applications in personalized medicine. One of the greatest challenges is to balance model realism and detail with experimental data to eventually produce useful data-driven models. We contribute to this quest by developing a transparent, highly parsimonious, first principle in silico model of a growing avascular tumor. We initially formulate the physiological considerations and the specific model within a stochastic cell-based framework. We next formulate a corresponding mean-field model using partial differential equations which is amenable to mathematical analysis. Despite a few notable differences between the two models, we are in this way able to successfully detail the impact of all parameters in the stability of the growth process and on the eventual tumor fate of the stochastic model. This facilitates the deduction of Bayesian priors for a given situation, but also provides important insights into the underlying mechanism of tumor growth and progression. Although the resulting model framework is relatively simple and transparent, it can still reproduce the full range of known emergent behavior. We identify a novel model instability arising from nutrient starvation and we also discuss additional insight concerning possible model additions and the effects of those. Thanks to the framework’s flexibility, such additions can be readily included whenever the relevant data become available.

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Emerging morphologies in round bacterial colonies: comparing volumetric versus chemotactic expansion

Cited by 25 publications

References 59 publications

Influence of Physical Effects on the Swarming Motility of Pseudomonas aeruginosa

Influence of Physical Effects on the Swarming Motility of Pseudomonas aeruginosa

Nonuniversality of front fluctuations for compact colonies of nonmotile bacteria

Morphological Stability for in silico Models of Avascular Tumors

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