noun
bacteriology
The scientific study of bacteria, often as a branch of microbiology.
彼は大学で細菌学を専攻している。
He is majoring in bacteriology at university.
微生物学 (microbiology) is a broader field that includes the study of bacteria, viruses, fungi, and other microorganisms, while 細菌学 focuses specifically on bacteria.
Compound of 細菌 (bacteria) + 学 (study, -ology). The term is a straightforward Sino-Japanese academic compound.