Translation guide
The Japanese word for bacteria is 細菌 (saikin). In everyday conversation, バイ菌 (baikinn) is often used for germs in general, including bacteria. For scientific contexts, バクテリア (bakuteria) is also used.
The learner wants to refer to bacteria in a neutral or scientific context.
Standard term for bacteria, used in medical, biological, and formal contexts.
細菌は目に見えない。
Bacteria are invisible to the naked eye.
この薬は細菌を殺す。
This medicine kills bacteria.
Loanword from English, used in scientific or technical contexts, sometimes in everyday speech.
腸内には多くのバクテリアがいる。
There are many bacteria in the intestines.
The learner wants to talk about germs in everyday conversation, often with a negative connotation.
Common informal term for germs, including bacteria, viruses, and other microorganisms. Often used when talking about cleanliness or illness.
手にバイ菌がついているよ。
There are germs on your hands.
バイ菌が入らないように消毒する。
Disinfect to keep germs out.
Short for 細菌 or バイ菌, used in compounds or casual speech. Can mean bacteria, fungus, or germ depending on context.
菌が繁殖する。
Germs multiply.
The learner wants to refer to good bacteria, such as in fermented foods or gut health.
Literally 'good bacteria', used for beneficial bacteria like probiotics.
ヨーグルトには善玉菌が含まれている。
Yogurt contains good bacteria.
細菌 is the formal, scientific term for bacteria. バイ菌 is a casual, everyday word for germs (including bacteria, viruses, etc.) and often carries a negative nuance. バクテリア is a loanword used in scientific contexts or when emphasizing the biological category.
In English, 'germs' can include viruses, but in Japanese, 細菌 specifically means bacteria. For viruses, use ウイルス (uirusu). バイ菌 can informally cover both, but in precise contexts, distinguish them.
Lactic acid bacteria, commonly mentioned in food and health contexts.
乳酸菌は腸にいい。
Lactic acid bacteria are good for the gut.