Can someone with a Ph.D in microbiology and immunology work in and possibly run a lab at a medical center?

Question

If it's possible what could they do. Is it necessary to have an M.D.

Answer 1

If it is a medical center managed by a university then that is possible, MDs might ask for guidance based on your degree and field of study. As far as running a lab, yes that is possible too, that's what a PhD degree is for.  

Answer 2

I believe the M.D. is required for positions such as medical director, director of pathology, chief pathologist or similar titles, but you could definately work as a pathologist and head up a particular department.  We have a perinatal pathologist at my facility (hospital) with a Ph. D in microbiology and immunology.