Wadsworth Center's Featured Image - Archives
This image shows the relative importance of nucleoid proteins in bacterial transposition, the process by which genetic elements called transposons jump from one chromosomal location to another. Transposons are discrete segments of DNA found in all organisms from bacteria to humans, and their study has important medical and evolutionary consequences. Nucleoid proteins playing a critical role in the compaction and structure of the bacterial chromosome were eliminated from three Escherichia coli strains, each containing a different transposon. Transposons contain a cryptic lacZ gene, which is activated following transposition to make b-galactosidase, which cleaves a colourless dye in the media that turns blue. Any cells within a colony undergoing a successful transposition event are detected as blue papillae (small micro-colonies) on a white colony. The columns, from left to right, represent strains with different mobile elements, and the rows show derivatives engineered to disrupt nucleoid proteins. The top panel indicates that wild-type strains undergo many transposition events, evidenced by the multiple papillae. The lack of papillae in an hns-deficient strain (second row) shows the critical role of the histone-like protein, H-NS, for transposition in E. coli.
Credit: Dr. Keith Derbyshire and Bryan Swingle
This series of papillation assays appeared on the cover of the May 4, 2004, issue of Molecular Microbiology.
