Studies of virgin tumuli, carried out since 1973, have focused on damage to the tumuli from microorganisms, the means of controlling the microorganisms in excavated tumuli, and the natural microorganism controls in the tumuli. Microbial counts in the Takamatsuzuka Tumulus have been high; fungal colonies appeared on the murals in 1975; the fungi were identified. The Roazuka tumulus in contrast was much better sealed, but examination indicated that despite closure the site was not free of bacteria or fungi. Paraformaldehyde has been used to control the fungi. Decomposition of the original buried body produces low molecular weight alkyl amines in a gaseous state; it has been proposed that the presence of this material had kept the closed tumulus in a microbial homeostasis.