_:b1218091 . _:b1218091 "A multi-layered sheet of micro-organisms, mainly bacteria and archaea. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces but a few survive in deserts."^^ . _:b1218091 . _:b1218091 . _:b1218091 "Wikipedia:Microbial_mat"^^ .