Fractal enzyme(s)
I missed this paper in Nature last week, which reports "the discovery of a natural protein, citrate synthase from the cyanobacterium Synechococcus elongatus, which self-assembles into Sierpiński triangles." Such a multilevel molecular fractal pattern is interesting for a variety of reasons: (1) all examples of complex fractal biomolecules are engineered; (2) the fractal does not seem to serve a physiological function in vivo -but also does not interfere with the citrate synthase function; (3) the metabolic cost of producing this complex structure is not prohibitive: it happens naturally.
The authors suggest that it is simply an evolutionary accident due to the spontaneous self-organization of the molecule's assembly. It could also be a stepping stone toward more complex functions, I hope they continue exploring possible uses of that molecule.
The reason this is fascinating to me is that the genomic representation of such a complex-looking molecule is compact. In other words, the logical depth of the code, provided the right computing machinery (here, physical self-organization), is small: "simply" repeat a loop. The cost of producing the modules and the time it takes to produce and assemble them are the only barriers. That should guide the search for more examples of complex bacterial biomolecules.