菌
きん · kin · JLPT N3 · noun
source
🦠🍄 菌 = 艹 plant + 囗 enclosure + 禾 grain: what grows on grain shut in a store
菌 first meant a mushroom or fungus, which is why it carries the plant radical 艹. Its sound-alike is 'kin': germs are uninvited kin that move in and multiply. You'll see it in 細菌 (saikin, bacteria) and 殺菌 (sakkin, sterilisation).