Thursday, 6 April 2017

proteins - Macromolecule levels in daughter cells after fission


When a prokaryote undergoes binary fission, how are the non-DNA macromolecules distributed between the two daughter cells? This is motivated by comments on a previous question and a G+ discussion. I am primarily interested in explicit mathematical models.





Naive model


For DNA, each copy is attached to a different part of the cell membrane, to ensure each of the daughters receives a copy. As far as I understand, there isn't such specific mechanism in place for other macromolecules. If we are allowed to assume that non-DNA macromolecules are distributed uniformly through the parent cell than this would mean the two daughter cells would receive half the proteins within statistical fluctuation. This has a specific meaning: if there are $N$ molecules of type A in the parent, then the difference in number of type A molecules in the two daughters after fission will be on the order of $\sqrt{N}$.


However, this model might be wrong. For instance, as the new cell-wall is being formed it could have in it specific pumps that either balance the protein levels below chance (producing an average difference lower than $\sqrt{N}$) or to create asymmetries higher than chance. Altenrnatively, the initial distribution of macromolecules in the parent could be far from symmetric for some other reasons. Which is the case?


If the naive model is correct, is there experimental evidence explicitly showing this?




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