Solved cryptogram
The structures that make energy in your cells were once free living bacteria in their own right.
Biology Facts, sourced to NCBI Bookshelf.
What it means
Mitochondria have their own circular genome, their own ribosomes and a double membrane, and they divide independently of the cell around them. All of that is what you would expect of a bacterium that was engulfed and never digested. The partnership is now so complete that neither side can live without the other, and it may be the single event that made complex life possible.
The claim comes from NCBI Bookshelf, and the page it comes from was read on 2026-08-27 to confirm it still says this.
This is not the kind of claim that goes out of date, which is why it was set as a puzzle rather than a fact with a shelf life.
Solve it yourself
This fact is a cryptogram here: 79 letters over 20 different ones, graded medium.
- SourceNCBI Bookshelf
- CollectionBiology Facts
- Difficultymedium
- Length79 letters, 20 of them different
Nearby in the collection
The facts either side of this one.
- National Human Genome Research Institutehard, 67 letters
- National Human Genome Research Instituteeasy, 77 letters
- NCBI Bookshelfeasy, 71 letters
- PLOS Biologymedium, 75 letters
About as hard as this one
Scored closest to it by the model behind our guide to solving cryptograms.
- MedlinePlusmedium, 68 letters
- NIDCDmedium, 68 letters
- MedlinePlusmedium, 69 letters
- National Human Genome Research Institutemedium, 74 letters