Escherichia coli K-12: a cooperatively developed annotation snapshot - 2005

The goal of this group project has been to coordinate and bring up-to-date information on all genes of Escherichia coli K-12. Annotation of the genome of an organism entails identification of genes, the boundaries of genes in terms of precise start and end sites, and description of the gene products. Known and predicted functions were assigned to each gene product on the basis of experimental evidence or sequence analysis. Since both kinds of evidence are constantly expanding, no annotation is complete at any moment in time. This is a snapshot analysis based on the most recent genome sequences of two E.coli K-12 bacteria. An accurate and up-to-date description of E.coli K-12 genes is of particular importance to the scientific community because experimentally determined properties of its gene products provide fundamental information for annotation of innumerable genes of other organisms. Availability of the complete genome sequence of two K-12 strains allows comparison of their genotypes and mutant status of alleles

The role of gyrA, gyrB, and dnaA functions in bacterial conjugation

The role of DNA gyrase in F'lac plasmid conjugation was studied using Escherichia coli gyrA43 (Ts), gyrB41(Ts), and dnaA46(Ts) thermosensitive mutants as donor or recipient organisms, and a rifampicin or nalidixic acid-resistant J-53 strain in the presence or absence of nalidixic acid. Mating experiments were also performed employing Hfr derivatives of the thermosensitive strains. Conjugation was carried out in broth for 60 min using a standard method at permissive and non-permissive (32 and 43 °C) temperatures, with or without drugs. At 32 °C, nalidixic acid reduced the number of transconjugants by about 97 % in comparison to the control, while at 43 °C, the drug inhibited F'lac transfer by about 98 % from dnaA46(Ts) mutant and by about 6.5 % from gyrA43(Ts) and 15 % from gyrB41(Ts) hosts. Using the temperature-sensitive mutants as recipient strains, the transconjugants found were approximately the same under all conditions. The number of transconjugants did not change significantly when nalidixic acid-resistant strains were used as donor or recipient strains. Lastly, nalidixic acid reduced the number of transconjugants from Hfr selected in the above mutants under all experimental conditions. These findings suggest that F'lac transfer does not involve DNA gyrase activity