Black swimming dots (BSDs) are nanoscale dot-like contaminants in the dishes of cultured cells. Until now, the identity of BSDs has not yet been determined. In our recent study, we proposed that BSDs per se are nonliving inorganic nanoparticles yet should derive from the cells infected with an unidentified airborne pathogen. We showed the pathogen possessed the characteristics including airborne transmitted, cell-dependent, insensitive to antibiotics, filterable through 0.1 m membrane. These properties prompt us to speculate that the pathogen of BSDs might be one kind of unidentified virus-like organism. However, the imperfection is that we have not isolated this putative pathogen from BSD+ samples [1]. Here, we report a further investigation of finding the virus-like pathogen in the serum and tissue extracts from BSD+ mice. Most importantly, this virus-like pathogen can be reisolated from the BSD+ extracts-inoculated, diseased BSD- cells.\n\nTo de ...