Mold, mildew and bacteria can grow on any basement wall. However if your basement walls bulge or buckle you may have a more serious problem. A sturdy basement with minor cracks can be done your self.
Before you start sealing any cracks, determine where your moisture is seeping through. Some cracks you will be able to see, some may be dripping water. You can find hard to find leaks with a sheet of plastic and duct tape.
Some places you can check for leaks is the snap ties holding the concrete forms together. These are metal rods, and they can rust, and then create water conduit in the basement. Visible dimples or round holes in the walls leaking moisture is caused by the seal to these rods has fallen off. A easy fix to this problem is to chisel the hole out, and refill with hydraulic cement.
Water seeping through will look unsightly on your basement walls, these come from small cracks. You can seal these cracks with expanding polyurethane form. With this foam it will expand and plug the crack. This will not work however for bowing and buckling walls. Basement walls that are in this shape will need to be replaced or reinforced with steel if they start to collapse.
Bowing walls can also be saved with installing proper supports. This will have to be done by a professional.