Microorganisms are microscopic organisms that can exist as single-celled or colonial organisms. They play key roles in nutrient cycling, biodegradation, climate change, food spoilage, and disease. Microorganisms include bacteria, fungi, archaea, viruses, and protozoans. Some bacteria like E. coli, Staphylococcus aureus, and Streptococcus pyogenes can cause illnesses, while others like Salmonella Typhi cause typhoid fever. Viruses such as coronaviruses, poxviruses, retroviruses, HIV, rabies virus, and rhinoviruses can also make humans and animals sick. Fungi include mushrooms, Trichophyton rubrum, Pen