I would think that would depend on the font size, but if we take the average size of a bacteria and for this instance I guess we can go by a really abundant bacteria Escherichia coli which is about 7 μm long and 1.8 μm in diameter.
That puts it about 1/25,000th of an inch. So you could place thousands of bacteria in one period. But again this is all based on which bacteria we are talking there is some very large bacteria that can be 750 μm that would be visable to the naked eye.
