One of the most widespread microorganisms in the world has been found to produce vitamin B12. It does it to such an extent that it is believed to be the provider of B12 to innumerable numbers of marine organisms all over the world that need it.
In my blog posting "A new B12 source is discovered – the missing link for vegans?" I am discussing the possibility that this might potentically be a B12 source for vegetarians. See