Read more: "Not so simple: Bugs that break all the rules"
One bacterium breaks two rules: it's got something like a nucleus, and it swallows its food
The defining characteristic of simple cells, or prokaryotes, is supposed to be the fact that their DNA floats freely in the cell rather than being enclosed in a nucleus. Indeed, the term "prokaryote" means "before nucleus".
Then, in 1991, John Fuerst and Richard Webb of the University of Queensland in Brisbane, Australia, noticed something strange about Gemmata obscuriglobus, a bacterium first described in 1984. It seemed to have "packaged" DNA. Images taken with an electron microscope confirmed that not only was its DNA separate from the rest of the cell, it was enclosed by a double membrane - just like the membrane envelope surrounding the nucleus of complex cells.
So is G. obscuriglobus, along with other members of the Planctomycete group ...
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