Fungi are multicellular, eukaryotic organisms, while bacteria are single-celled prokaryotes. The cells of fungi have nuclei that contain the chromosomes and other organelles, such as mitochondria and ribosomes. Bacteria are much smaller than fungi, do not have nuclei or other organelles and cannot reproduce sexually.
All eukaryotes, including plants, animals and fungi, have cells with nuclei and a large assortment of complex organelles that are used to carry out various biological functions. Fungi have cell walls and reproduce both sexually and asexually through the use of spores. They are unable to photosynthesize and must absorb nutrients by breaking down organic material. Many species of fungi play important roles in ecosystems by decomposing dead plants and animals. Scientists estimate that there are more than 2 million species of fungi on Earth.
Bacteria are one of the two main types of prokaryotes along with the archaea. Unlike fungi, their cells do not contain nuclei. Instead, their DNA is found on a circular chromosome that floats around in the cytoplasm. Bacteria generally reproduce through fission, producing two identical daughter cells. While bacteria can join together into complicated structures known as biofilms, they are not genuine multicellular organisms. Instead, each individual bacterium remains a separate organism.