For decades, researchers have tried to find eukaryotic cells that don't have mitochondria — and for a while they thought they'd found some, like Giardia, a human gut parasite that causes diarrhea, that has some kind of remnant mitochondrion instead of mitochondria.
However, after scientists from Charles University in Prague have sequenced the genome of the gut microbe that had been isolated from a researcher's pet chinchilla, expecting to find that kind of vestigial mitochondrion, they actually found no trace that it made any mitochondrial proteins at all.
That means they have found a complex cell that survives without mitochondria.
http://www.npr.org/sections/health-shots/2016/05/12/477691018/look-ma-no-mitochondria
However, after scientists from Charles University in Prague have sequenced the genome of the gut microbe that had been isolated from a researcher's pet chinchilla, expecting to find that kind of vestigial mitochondrion, they actually found no trace that it made any mitochondrial proteins at all.
That means they have found a complex cell that survives without mitochondria.
http://www.npr.org/sections/health-shots/2016/05/12/477691018/look-ma-no-mitochondria