This is Part 4 of our four-part series, Microbes on a Mission. Read Parts 1, 2, or 3 before diving in, or start here. Part 1: How Plastic-Eating Microbes Could Clean Up Our Oceans Part 2: How Microbes Can Be Genetically Engineered to Clean Contaminated Soil Part 3: Could Engineered Bacteria Remove Greenhouse Gases From the Air?