Bacillus subtilis var. natto
Japanese: 納豆菌（Bacillus subtilis var. natto）
A variety of Bacillus subtilis that ferments soybeans into natto. It possesses powerful proteolytic enzymes and produces natto's characteristic stickiness and aroma.
Natto bacteria naturally inhabit rice straw as a variety of Bacillus subtilis. When they colonize steamed soybeans, their powerful proteases break down proteins and spin out threads of polyglutamic acid—natto's signature stickiness.
Their vitality is remarkable. They form endospores that withstand boiling water, surviving harsh conditions with tenacity. This is precisely why natto has been made for centuries by the simple method of wrapping soybeans in straw.
Their reproductive vigor is so strong that sake and miso breweries sometimes post warnings: please do not eat natto.