Any Microbial biology majors at Cal?

I’m really into microbiology but I’m pre med at the same time.
From what I see, the microbiology classes at Cal don’t seem that GPA friendly.
Especially with PMB C112(Gen. MB) or PMB C148(Microbial Genetics)
Why is that so? Are the classes that hard? Do you recommend the major?
Any advice would be thankful