This is an absolutely fascinating and highly accessible article on the massive proliferation of known microbial species (and melting pots of quasi-species) as we become (slightly) more able to detect them.
The most prevalent organism on Earth, a free-swimming ocean microbe called Pelagibacter ubique, was only identified in 1990, and not successfully cultured until 2002. A class of bizarre microbes that make hydrazine (rocket fuel) as a metabolic intermediate turned out to be responsible for half the ocean’s nitrogen production, even though scientists until the 1990’s were skeptical that their brand of metabolism was even possible. These organisms, the annamox bacteria, were not identified until 1999. The list of these things is endless.