The important point is that the surface area to the volume ratio gets smaller as the cell gets larger. Thus, if the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume.
At dawn the squid prepares to hide in the sand for the day and it ejects about 95% of the bacteria from the light organ in order to reduce or stop the growth of bacteria population in the squid. This will prevent the bacteria population from reaching a level too high for the squid to support.
