the ancestor of prokaryotic cells. it was basically a bunch of organic molecules surrounded by a membrane. they exhibit some properties associated with living organisms, such as reproduction, metabolism, and what may be a precursor to homeostasis. they may have formed spontaneously in the conditions found on earth around 3.8 billion years ago or perhaps even farther back.
*in Biology class*

"OH MY GOD. Dude. I just found an organism that is way too small to be considered a bacteria, but it seems to reproduce and metabolize itself."
"Yeah, you have a nanobacterium on your hands."
"WTH is a nanobacterium?"
"Oh, nothing, just an organism that some scientists don't consider an organism. It's totally real, though, because it's a modern protobiont."
"WTH is a protobiont?"
"HOW are you in biology?? Just look it up on Urban Dictionary."
by alee-marie September 09, 2012

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