| Citation | Dixon has made major contributions to understanding the genetic basis of nitrogen fixation - a process of fundamental biological importance. He was one of the first two scientists to demonstrate intraspecific transfer of nitrogen fixation (nif) genes, and he transferred the complete nif cluster from Klebsiella pneumoniae to Escherichia coli, so creating the first 'engineered' nitrogen-fixing microbe. He constructed transferable nif plasmids which became widely-used tools for nif gene analysis in all diazotrophs and over the next fifteen years he played a leading part in their exploitation to map and clone the 20-gene nif cluster of K. pneumoniae, to dissect its functional complexities, and to analyse its regulation. Using purified regulatory components, he was first to demonstrate long-range transcriptional activation in prokaryotes; more recently he has implicated phosphorylation in modulating activator activity. |