Mechanisms of recombination and function of DNA in bacteria. Progress report, August 12, 1978-August 15, 1979

Most work in the current period centered on the organization and transfer of two classes of drug-resistance determinants in pneumonococcus: (a) insertions of foreign DNA in the chromosome; and (b) plasmid carried genes. Major findings are: determinants for chloramphenicol and tetracycline resistance in some clinical isolates of pneumococcus are present as adjacent insertions of heterologous DNA into the normal chromosome. They are not carried on plasmids as are similar determinants in many species; pneumonococcus will support the growth of resistance plasmids from other streptococci, and these can be transformed into pneumococcus from lysates of S. faecalis (group D) or group B streptococcus; one of the plasmids that has been transformed into pneumococcus mediates a form of DNAse-resistant conjugal transfer among other streptococcal groups and also in pneumococcus. (PCS)