An incredibly simple way of making bacteria create little solar cells: http://www.bbc.co.uk/news/science-environment-40975719

It seems that cadmium is seeded into bacterial culture and then the cadmium is crystallised, as a sulfide compound, on the surface in the form of semi conductors. The presence of cadmium is a limiting factor here.  How much of it is present in the Earth (estimates?) and what is the use of the acetate which is made as a photosynthetic product?  IMHO, this is exciting but at the first stage of making a useable fuel source for humans.

5 minutes ago, jimmydasaint said:

The presence of cadmium is a limiting factor here.  How much of it is present in the Earth (estimates?)

0.1 parts per million (the 65th most common element). A bigger problem is that it is extremely toxic. It has been replaced in nearly all of the industrial uses it had in the past.

Thanks for that quick answer.  Of course, heavy metals are required for the photochemisynthetic method. That makes it a health and safety hazard then and so unlikely to be used unless there is a secondary reaction where the acetate made is converted into a carbon-based fuel.  That is  a whole new field of investigation.