A fungus is a type of eukaryotic organism that includes microbes like yeasts and molds, as well as the more well-known mushrooms.
A primitive organism is a fungus.
Fungi, like animals, are heterotrophs, meaning they feed by absorbing dissolved molecules, which they do by secreting digestive enzymes into their environment.
Fungi do not have the ability to photosynthesize.
Mycoplasma:
Mycoplasma is not a fungus; it is a type of bacteria.
Although a Mycoplasma's normal size and shape is a 0.2-0.3 micrometer diameter sphere – a tenth the width of a typical bacterium – they can also be bigger and swollen or branched or unbranched threads of various lengths that resemble fungal filaments rather than bacteria.
They initially mistook it for a virus or fungus, so they named it "mycoplasma," which means "fungus-formed" in Greek.
Scientists eventually discovered that it is a bacterium with numerous distinguishing features.