Beneficial bacteria
Escherischia coli bacteria in your intestines help you digest food. They also make vitamin K and vitamin B12.
Bacteria living inside the roots of plants, such as alfalfa, take up nitrogen gas from the air and convert it into a form the plant can use (nitrates)
A few bacteria produce antibiotic drugs such as streptomycin and nocardicin.
Bacteria used in the food industry convert milk to buttermilk and yogurt, and wine to vinegar.