I've seen on Wikipedia; that set covering cannot be approximated in polynomial time to within a factor mentioned above. Unless $NP$ has quasipoly-time algorithms.
Now, this must pertain to classical algorithms and does not mention any approximation algorithms that may only work in nature.
(eg. Things like Amoebas solving $TSP$ problems)
Do any single-cell organisms show any promise in solving $NP$-hard problems in polynomial-time?
Or approximating them better than any known classical algorithms?