Inorganic since bricks are burned at high temperature and all organic
material is incinerated.
Affections by Cladosporium is possible when the bricks are exposed to constant damp or there is damp in its pores and if nutrients are available in sufficient quantities. These affections are the most severe you can get and are very hard to get rid of.
When the black mould has gotten a hold, it establishes itself fast.
All black mould, its spores and the surface must be sterilized and disinfected for the affections to stop. Future affections become impossible for the next four years.