There are no strict guidelines for writing your personal statement - that's what makes it personal. However, the personal statement is a very important part of the application and the following features are typically helpful for the Admissions Committee:

• It should be your work and reflect you, although it's fine to get input from others.
• It should include some description of your research experience. Research experience is a critical component in the admissions decision. If your research experience is not mentioned in your personal statement and/or your recommendation letters, the Committee won't know about it.
• It should address the question: Why are you interested in attending graduate school, at the University of Wisconsin, in the Microbiology Doctoral Training Program?
• It may include your thinking about career plans, although it's early in your scientific training and nothing's set in stone.
• The personal statement can be a place to address discrepancies, relative weaknesses, or anything potentially atypical that may arise in viewing your application, e.g., if you had low grades in one particular semester, took time during or after college for another endeavor, are making a change in career direction or scientific field, etc.