Microbiology does not necessitate the use of math. Memorization rather than calculation is the primary method of learning the material. For an accurate estimate of the size of the populations you might be observing, you'll need to know a little bit about exponents (or at least how they work). You won't have to do much arithmetic on most microbiology exams. However, you may be asked to examine and evaluate graphs. Especially when plotting growth rates over time.