Hi thebreath,
I've got some similarities with your background, and here's what I know from personal experience:
1. I got a BS in Biotech, and a MS in Biology from the CSU, and the Unis that I applied to for a Microbiology PhD didn't look down on that.
2. Astrobiology is a tough field to get into, but if you're interested in it, try to apply to Unis that have a link to NASA. UC Merced and UC Riverside (my school, which I really enjoy) both have NASA MIRO funding, which can definitely be used for grad students. I got a 2-year fellowship through NASA to work in microbiology. It looks good on a CV to have NASA funding if you want to work for them in the future!
Good luck!