Origin & Evolution of Life

The Reproduction Process Of Gram-positive Protocells

By Keith Cowing
Press Release
biorxiv.org
December 20, 2022
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The Reproduction Process Of Gram-positive Protocells
Growth characteristics of EM-P in batch culture. EM-P exhibited a typical sigmoid growth curve with an initial phase of slow growth rate (lag phase), a log phase with exponentially increasing cell numbers and a gradual decline in the growth rate during the stationary phase. The X and Y-axis in the plot indicate the time in hours (h) and optical density. Images A & B shows typical morphologies of cells in early and late lag-phase (notice an increase in the size of the cells). Images C – I, show early log phase cells that seems to be reproducing either by binary fission (C, D and Video 2 & 3) or budding (arrows). Images F – I show variation in the sizes of the daughter cells (buds). Scale bars: 10µm. — biorxiv.org

Protocells are, by definition, the most primitive predecessors of biological cells, devoid of all complex molecular biological processes.

They are believed to have mediated reproduction entirely by physicochemical forces.

Despite these propositions, little is known about the actual mechanisms. To understand the reproductive process of protocells in their native habitat, here we used a top-down approach to transform bacterial cells into a primitive lipid vesicle like state in which cells are devoid of molecular biological mechanisms regulating their reproduction.

Given protocells existed on early Earth, we conducted all our experiments under the presumed environmental conditions of Archaean Eon Earth. Even in the absence of functioning biological processes, cells under these conditions reproduced in a defined sequence of steps, always leading to the formation of viable daughter cells.

Their reproduction mechanism can be explained by the interaction between intracellular metabolism, physicochemical properties of cell constituents, and environmental conditions. Based on our observations, we propose that reproduction may be an inherent property of cells with an internal metabolism without the need for dedicated molecular biological processes.

Competing Interest Statement

The authors have declared no competing interest.

Dheeraj Kanaparthi, Marko Lampe, Jan-Hagen Krohn, Falk Hildebrand, Thomas Boesen, Andreas Klingl, Prasad Phapale, Tillmann Lueders
doi: https://doi.org/10.1101/2021.11.25.470039
https://www.biorxiv.org/content/10.1101/2021.11.25.470039v4

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