As the concentration of gold is so small, it's not really economically feasible, let alone a way to get rich. More like an interesting biological anomaly.
Frankly, it may be more trouble to get all the permits and handling and blahblahblah to have a vat of toxic heavy metals on the offchance that you happen to find the microbial equivalent of the Philosopher's Stone than benefit you'll reap from it, @Orion Bailey .