Self-reproduction and doubling time limits of different cellular subsystems.

Ribosomes which can self-replicate themselves practically autonomously in beneficial physicochemical conditions have been recognized as the central organelles of cellular self-reproduction processes. The challenge of cell design is to understand and describe the rates and mechanisms of self-reproduction processes of cells as of coordinated functioning of ribosomes and the enzymatic networks of different functional complexity that support those ribosomes. We show that doubling times of proto-cells (ranging from simplest replicators up to those reaching the size of E. coli) increase rather with the number of different cell component species than with the total numbers of cell components. However, certain differences were observed between cell components in increasing the doubling times depending on the types of relationships between those cell components and ribosomes. Theoretical limits of doubling times of the self-reproducing proto-cells determined by the molecular parameters of cell components and cell processes were in the range between 6-40 min.