One can learn MCAT microbiology straight from the MCAT prep books or courses. It is not indepth, and merely stems from everything you learned in your first quarter of biology.
If there's anything new, it'll be provided in a passage, and if you have at least avarage reading skills it should not be a problem to glean this information.
With regards to physiology, thats a big generalized class. Many aspects can be covered by the MCAT, from reproduction to the central nervous system, and beyond. Although one can actually learn this from the MCAT books too, i personally think it would be better to have been exposed to this course before taking the MCAT.
SO my suggestion would be take physio.