These silica transport proteins are unique to diatoms, with no homologs found in other species, such as sponges or rice. Mann in Adl et al. This material is then extruded to the cell exterior and added to the wall. The sequences compared in this study were used to create a diverse background in order to identify residues that differentiate function in the silica deposition process. Diatomaceous earth is used for a variety of purposes including for water filtration, as a mild abrasive, in cat litter, and as a dynamite stabilizer. : J. Seckbach. Mann in Adl et al. Origin of diatom 1835–45;