Death of unicellular organisms is brought about by the inactivation of a certain number of essential molecules in the cell.
If the number of these essential molecules is only one per cell, the order of death is the same as if the cell were identical with this molecule; the order of death is logarithmic following the mass law.
If more than one molecule must be inactivated before the cell dies, the order of death is not logarithmic. With 2 or 3 molecules, it still resembles the logarithmic order, but with an increasing number of reacting molecules, it approaches more and more the order of death known with higher organisms, namely a period of no death, followed by a comparatively short period of rapid death.
The decision whether or not the logarithmic order exists, should be based upon the constancy of the death rate
See PDF for Equation.
The existence of a straight line when logarithms of survivors are plotted against time, is not sufficient proof unless the initial number of cells is included.
These deductions are made with the assumption that all organisms are exactly alike, and show no individual variations or graded resistance.
With most bacteria, the order of death is so nearly logarithmic that death must be brought about by the inactivation of only one molecule, though there may be several molecules of this same type in each cell.