Chemical studies in host-virus interactions; immunochemical studies on the purity of concentrates of various bacterial viruses prepared by differential centrifugation procedures with an appendix summarizing data on the desoxyribonucleic acid content of these viruses.

Three mutant pairs of bacterial viruses T2r(+) and T2r, T4r(+) and T4r, T6r(+) and T6r, have been concentrated by differential centrifugation and analyzed. Under conditions of prolonged lysis of organisms grown on broth-agar, the virus concentrates frequently contained phosphorus (P) other than that contained in desoxyribose nucleic acid (DNA). These concentrates reacted with antisera to the host organism, E. coli, specifically precipitating the non-DNA-P but not virus activity or DNA. The amounts of nitrogen precipitated in the virus concentrates by antisera were related to their content of non-DNA-P. These viruses could be purified by differential centrifugation after such treatment to yield preparations apparently free of P other than DNA-P. It has been concluded that there is no satisfactory evidence for the presence of ribose nucleic acid as a constituent part of these viruses.