Complex sentence: Leeuwenhoek may have observed "Vibrio" bacteria after his discovery of "animalcules" described in his letters to the Royal Society, as he described microorganisms with the same appearances and behaviors as bacteria belonging to the "Vibrio" genus.
Split into simpler sentences: Leeuwenhoek may have observed "Vibrio" bacteria after his discovery of "animalcules" described in his letters to the Royal Society. He described microorganisms with the same appearances and behaviors as bacteria belonging to the "Vibrio" genus.