Your lab experience seems pretty impressive to me and Plant Pathology, which deals very often with fungi and bacteria, should be a good match for many microbio programs. But I feel like you are wavering with yourself in what kind of research topic you are really interested. Maybe it would be also good to review your Statement of Purpose. If you give the reader of your Statement the impression there is a big chance that you change your mind in 1 or 2 years, the admission committee will be alerted, even if your overall qualifications are good. Since many people capitulate on their PhD after some time, programs often look for candidate who convincingly show that they are able to stand the 4-6 years required to get a PhD.