Question: Until fairly recently, prokaryotes were classified as a single group called Kingdom Monera. What has occurred to make scientists change microbial classification? Need Assignment Help? Scientists learned that amoebas were eukaryotes, whereas bacteria were prokaryotes. After the discovery of viruses, it became obvious that they belonged with other microbes. Most microbes now appear to be more closely related than we previously thought. Scientists learned that microbes were much more genetically diverse, even though they are all small. Scientists learned that true bacteria are more closely related to eukaryotes than archaeans.