Linkage map of Escherichia coli K-12, edition 10: the traditional map.

This map is an update of the edition 9 map by Berlyn et al. (M. K. B. Berlyn, K. B. Low, and K. E. Rudd, p. 1715-1902, in F. C. Neidhardt et al., ed., Escherichia coli and Salmonella: cellular and molecular biology, 2nd ed., vol. 2, 1996). It uses coordinates established by the completed sequence, expressed as 100 minutes for the entire circular map, and adds new genes discovered and established since 1996 and eliminates those shown to correspond to other known genes. The latter are included as synonyms. An alphabetical list of genes showing map location, synonyms, the protein or RNA product of the gene, phenotypes of mutants, and reference citations is provided. In addition to genes known to correspond to gene sequences, other genes, often older, that are described by phenotype and older mapping techniques and that have not been correlated with sequences are included.

Mapping information roadways from sequence to phenotype and across species.

Expressing genetic concepts in ways that allow computerization of detailed genetic information and connectivitity with molecular biology databases is discussed. Interconnections between and among organismal and molecular databases are illustrated with examples from E. coli and maize databases on the World Wide Web connecting with GenBank, SwissProt, and other databases. Issues in development, maintenance, and widespread public use of such information are discussed.

A comparison of internal standards for plant cytophotometry.

Plant cell nuclei were compared with chicken erythrocyte nuclei for use as internal standards for microspectrophotometry. The amount of DNA per nucleus and the coefficient of variation for measurement of individual nuclei were determined for cells from dormant embryos of Pinus taeda and Pinus coulteri, from onion root tips and from chicken erythrocytes. The chicken erythrocytes had the least variability and thus were best suited for use as a standard. Onion root tips were least suitable, with a coefficient of variation 2 1/2 times that of erythrocytes. Although onion root tips have been used as an internal standard in other studies, their mitotic activity, in contrast with the nonreplication of DNA of mature erythrocytes, is reflected in a broad distribution of nuclei with values in the 2C-4C range. Coulter pine mature embryos were at the 3C level, whether dry or hydrated, while loblolly pine embryos were in the 2C state. This confirms previous reports. The coefficient of variability for the pine embryo cells was 1 1/2 times that of erythrocytes for nonhydrated seeds and twice the erythrocyte value for hydrated seeds. The larger 2C values for pine (26 pg for P. taeda and 17 pg for P. coulteri) are closer to values expected for many plant species than the 3 pg level of the chicken erythrocytes. Dormant P. taeda embryo cells (2C) are suggested as an alternative where the experimental material has large DNA values and/or chicken erythrocytes are difficult to procure. Large sample size is recommended for the plant materials if they are to be used as internal standards in Feulgen cytophotometry.

Regulation of RNA polymerase synthesis in Escherichia coli: a mutant unable to synthesize the enzyme at 43 degrees.

We report the isolation of a mutant of E. coli in which the capacity to synthesize RNA polymerase (EC 2.7.7.6) (the beta and beta' subunits) is rapidly lost at 43 degrees. The mutation has no effect on the stability or activity of the polymerase itself. The mutation is recessive and is closely linked to the rif locus (the structural gene for the beta subunit). Using strains carrying the mutation, we have shown that polymerase is present in excess in rapidly growing E. coli cells.