Preheat the oven to 400 F. Have ready an ungreased nonstick baking sheet.
In a large bowl, combine the flours, wheat germ, baking powder, baking soda and salt. Whisk to blend. Add the butter to the flour mixture. With a pastry blender or 2 knives, cut the butter into the dry ingredients until the mixture resembles coarse crumbs. Add the buttermilk and stir just until a moist dough forms. Don't overmix. Cover the bowl with plastic wrap and refrigerate for 30 minutes.
Turn the dough out onto a generously floured work surface and, with floured hands, knead gently for 6 to 8 times until smooth and manageable.
Using a rolling pin, roll the dough into a rectangle 1/2-inch thick. Using a 2 1/2-inch round biscuit cutter dipped in flour, cut out biscuits. Cut close together for a minimum of scraps. Gather the scraps and roll out to make additional biscuits.
Place the biscuits about 1 inch apart on the baking sheet. Bake until the biscuits rise to twice their unbaked height and are lightly golden, 8 to 10 minutes. Serve hot.