In the phrase "The scientist looked at the bacterial culture through her microscope", the term culture matches the following definition from the Cambridge Dictionary: Cells, tissues, organs, or organisms cultivated for scientific investigation, or the practice of breeding and maintaining specific living entities to obtain their products. The key words are scientist, bacterial and microscope. These pertain to a specific domain of study, namely Biology or Science.
In the sentence, "My friends know I'm interested in culture, so they often ask me about music, plays, and books.", the term culture takes on a vastly different definition. Based on the dictionary, the fitting definition is: The arts that convey or demonstrate the traditions or lifestyle of a specific community or group; including literature, art, music, dance, theater, etc. Terms like music, plays and books serve as clues pointing to the definitions that describe how people express traditions and thoughts.
In the context of the last sentence, "My grandparents took me to Italy to learn about their native culture", the term culture conveys another idea associated with the characteristics of life, particularly the shared customs and beliefs of a community at a specific period. Here, grandparents and native act as indicators to help with selecting the correct meaning. They suggest a particular community from a certain time frame, rather than the current period.