Yes, like humans (all other animals on Earth), sharks have a gut microbiome too. Everyone’s just been way too busy talking about all that Megalodon crap to think about this *real* and much cooler science.
There is a diverse and abundant gut microbiome associated with finfish, sharks, and blue crabs. These gut microbiomes all have a core Proteobacteria community, which is in contrast to the human and terrestrial mammalian gut microbiome which is dominated by Firmicutes and Bacteroidetes ribotypes. This difference may partly be attributed to the fact that some of these Proteobacteria (such as Vibrio spp. and Photobacterium spp.) are typically associated with aquatic environments.