Without microorganisms, we would not have many of the green processes that provide us with useful commodities and important food supplements for healthier diets (e.g., vitamins). Without microorganisms, we would not have drugs to fight infections, treat cancer, allow organ transplants, or protect crops from pests. Without our microbial friends, we would not have delicious food and drinks (beer, bread, cheese, kimchi, wine, and yogurt, just to name a few) that allow us to store and transform grains, vegetables and dairy products.
So, would life without microorganisms be possible at all? Probably not. But even if it were, it would certainly be miserable.