There are a vast number of career options that you can pursue after B.Sc in Microbiology. It majorly depends on what is your dream job and the field you want to work in. If your dream is getting a research job in microbiology, you should pursue a masters in the same or related field (like biotechnology), followed by a Ph.D.
For pursuing Ph.D. in India, it’s important you clear the CSIR NET exam, with marks higher than the cut-off for jrf. For wanting to be a university lecturer, you would again need to clear the NET exam and get marks higher than the cut-off for lectureship.
Microbiology is a vast field, and students sticking to it take one of its specializations during their higher studies. You can be a clinical microbiologist, environment microbiologist, food Q/A expert, etc. Once you enter Masters, you will learn a lot about each specialization and can decide further based on what interests you.