This is the 10033rd most frequent Turkish word.
bakterilerin
"Of the bacteria" or "bacteria's" (possessive form).
In this sentence, 'bakterilerin' is used in possessive genitive form ('bakteri' + 'lerin') and defines 'the bacteria's' in terms of ownership referring to their action of multiplying.
Bakterilerin çoğalması için uygun ortam gerekir.
An appropriate environment is required for the bacteria to multiply.
Here, 'bakterilerin' is again in the possessive genitive form and specifies 'some bacteria's', pointing to the concept of bacteria affecting health.
Bazı bakterilerin sağlık üzerine olumlu etkileri vardır.
Some bacteria have positive effects on health.
In this example, 'bakterilerin' acts in the possessive genitive form, indicating 'the bacteria's', referring to their behavior in various environments.