CBBS Subgroup Contributed Talks

David Lacoste

Laboratory Gulliver, ESPCI, Paris

"Emergence of homochirality in large molecular systems"

The selection of a single molecular handedness among the two possible configurations of a given molecule, or homochirality, is observed across all living matter and is a mystery in the origin of life. Here, we show that large chemical systems, are likely to undergo a spontaneous symmetry breaking toward a homochiral state as the number of chiral species increases [1]. Through an analysis of a large chemical database, we find that there is no need of very large molecules for chiral species to dominate over achiral ones; it already happens when molecules contain about 10 heavy atoms.Refs: G. Laurent, D. Lacoste, and P. Gaspard, PNAS (2021) 118 (3) e2012741118; https://doi.org/10.1073/pnas.2012741118

Martijn de Jong

Leiden University

"Cellular Potts model of convergent extension can explain shape variability of gastruloids"

Gastrulation is a crucial process during embryonic development. During this process, the embryo elongates and cells start rapidly differentiating. We have studied an in vitro model of this process and noticed that the shapes of the resulting tissues had a wide variation. Here we show that a Cellular Potts Model (CPM), based on modified filopodial-tension of convergent extension after Belmonte et al. (P Comput Biol 2016) mimics the variability of the shapes closely. The model periodically places hookian springs between cells, which model filopdia pulling cells close to each other. If cells extend filopida in random polarization directions and align polarizations to their neighbors, the resulting tissues form two or multiple lobes, closely resembling the shapes formed by gastruloids. We analyzed the shapes using lobe contribution elliptic Fourier analysis (LOCO-EFA), which supports the observed qualitative similarities between simulations and gastruloids.

Robert Planque

Vrije Universiteit Amsterdam

"Stability of a reaction pathway adaptively controlled to maximise flux"

Single celled organisms such as bacteria and yeasts are able to tune enzyme levels that catalyze the reaction pathways by which they eventually make new copies of themselves. Depending on nutrient conditions, more or less enzyme is invested in different parts of their reaction network, so that reaction rates are constantly high, and cellular growth rate is maximised. In this talk I will present an analysis of a reaction network coupled to a set of equations for synthesis and degradation of enzymes involved in this network. These enzyme equations are designed such that the steady state flux through the network is optimal when it is in steady state. The resulting dynamical system is an ODE system with two sets of algebraic equations attached. I will discuss the challenges to analyse this system, including quasi-steady state analysis, local stability, and if we have succeeded by the time of this conference, also global stability.

Bime Markdonal Ghakanyuy

University of Buea, Cameroon

"Investigating the Impact of Multiple Feeding Attempts on Mosquito Dynamics via Mathematical Models"

A deterministic nonlinear ordinary differential equation model for the dynamics of terrestrial forms of the Anopheles sp mosquito population is derived and studied. The model is designed to capture and assess the impact of multiple probing attempts by mosquitoes that quest for blood meals in human populations. There exists a threshold parameter, whose nature is affected by the manner in which we interpret the transitions involving the different classes on the gonotrophic cycle path. The trivial steady state of the system, which always exists, can be globally asymptomatically stable for positive values of the threshold parameter that are less than unity. The non-trivial steady state, when it exist, is stable for a range of values of the threshold parameter but can also be driven to instability via a Hopf bifurcation. Our analysis reveals that waiting class mosquitoes contribute positively in sustaining mosquito populations. A nonlinear analysis, based on the center manifold theorem, is used to derive expressions for the amplitude and phase of the oscillating solutions that arise through Hopf bifurcations. We conclude that to understand the human-mosquito interactions, it is informative to consider multiple feeding attempts that are known to occur when mosquitoes quest for blood meals within humans.