"Given the absurd number of times bacteria have reproduced in the last 100+ years that we've been observing them (millions given the rapid rate of reproduction), how many new bacterial species have been seen? Any?"
Haven't looked for any new species of bacteria, but I have noticed that 500 lb pumpkins now exist. Granted, it took a little help from mankind, but that's exactly what Mother Nature does day in and day out. Help species evolve. I've also noticed that mankind is evolving. We're getting larger and dumber as time goes by.
(Pssst: That's not a new species. It's still a pumpkin).