Old King Midas thought being able to turn anything he touched in the gold was a good deal. However, it turned out having the Midas touch wasn't such a winning proposition. A certain type of bacteria is able to turn gold ions into harmless gold nanoparticles that accumulate outside of its cells.
The process is a defense mechanism that the bacteria uses because gold ions are toxic. The bacteria is Delftia acidovorans and while science has known about the process, it has only recently been described by researchers. The scientists believe that by understanding and describing the process that it may be possible to one day develop methods to retrieve gold out of the water that carries it.
The process could be used to design sensors able to identify streams and rivers rich in gold. The chemical protein in the bacteria that uses for the Midas-like process is called delftibactin A by the scientists. The bacteria secrete the protein into its surroundings when it senses gold ions. The protein then chemically changes gold ions into particles of gold ranging between 25 and 50 nm across.
Those particles then accumulate near the bacteria creating patches of gold. However, rather than having namesake golden color, the particles of gold created by this bacterial process make flakes that are a deep purple color. The scientists believe that if the delftibactin A is selected for gold it could be useful for gold recovery or as a biosensor.