Abstract: Novel autonomously replicating biological particles resembling bacteria and having most surprising properties were discovered from cell culture sera and other biological samples alleged to be sterile according to the current testing methods. These slowly growing agents named Nanobacteria are smaller than any known cell-walled bacteria. They pass through sterile filters, even with pore sizes smaller than their diameter. They cannot be cultured on any standard microbiological media. With the isolation and detection methods provided here they are commonly detectable in animal or human serum. This patent holds for methods of their culture, detection, purification, and elimination and described the necessary reagents for that.Autonomously replicating particles can be cultured in RPMI 1640, or in DMEM, or in other cell culture media. Optimal growth can be obtained by supplementing the culture medium with 10-20% sterile fetal bovine serum.