Chalmers Conferences, 9th European Conference on Mathematical and Theoretical Biology

Modeling the Directional Growth of Aggregated Archaeal Cells
Viktor Milkevych, Damien Batstone

Last modified: 2014-03-28


Members of the family Methanosarcinaceae are important archaeal representatives due to their broad functionality, ubiquitous presence, functionality in harsh environments, capacity to generate methane from simple molecules. The cells are strictly anaerobic and obtain energy from methanogenesis by catalyzing the terminal step of organic matter degradation process. A key characteristic is their multicellular morphology represented by the clusters of regular aggregates composed of spatially confined cells.

To assess the controlling and governing mechanisms defining the cells growth within aggregated (confined) state, we have applied theoretical model-based analysis. A confined elastic shell geometrical model was developed and justified for aggregated archaeal cells. Based on a work-energy principle, a general growth law for aggregated archaeal cell was derived. The growth law takes into account the fine structure of archaeal cell wall, polymeric nature of methanochondroitin layer, molecular-biochemical processes and is consistent with thermodynamics laws. This growth model assumes a partition function which splits available mechanical energy and defines the amount of energy that is transformed to pure growth and amount of energy that transformed to local structural changes of cell wall material. A simple form of the constitutive equation for the partition function has been introduced. The developed model was applied to three different configurations of an aggregated cell, and supported by finite element numerical calculations in 3D. The model predicted directional growth that is analogous to geometry sensing, and slowed growth of confined archaeal cells (based on mechanistic principles), as well as sequential changes in direction of growth during the consecutive growth-division stages. A key outcome is that cell sensing and growth anisotropy can be predicted using simple cellular mechanisms without the need for dedicated cellular machinery.  This means that many of the more characteristic features of Methanosarcina, including tetrad morphology can be derived from mechanical principles rather than complex molecular causes.