An interesting recent development is a growing awareness of bacteria. It's now realized that the total biomass of bacteria on earth far outweighs all animals, plants, and other complex living beings put together. A recent claim is that "there are 10 times as many bacterial cells in a typical human body as there are human cells." If we don't count blood and bone (about 20% of your mass) estimate the fraction of your mass that is bacterial and not "you".