Allen Kerr

University of Adelaide

Primary Section: 62, Plant, Soil, and Microbial Sciences
Secondary Section: 25, Plant Biology
Membership Type: International Member (elected 1991)

Research Interests

My most important research has been on the biological control of crown gall, a plant disease caused by Agrobacterium tumefaciens, a soil-inhabiting bacterium that colonizes the roots of plants. As a result of my work, the disease can now be controlled biologically, using a closely related, non-pathogenic strain of Agrobacterium. To improve control efficacy, a genetically engineered organism to be registered as a pesticide and released for general use. Control is dependent on the production of an antibiotic called agrocin 84 by the controlling organism. The chemical structure of agrocin 84 was determined and the genes controlling its synthesis located on a 47.7 kb plasmid. Another important aspect of my work has been on conjugation in Agrobacterium. I demonstrated that pathogenicity in Agrobacterium could be transferred from one bacterium to another. This was of crucial importance in the demonstration by others -- that pathogenicity is encoded by a large plasmid, the Ti plasmid. I showed that opines, chemicals present in crown gall tissue, can induce conjugation. This was the first example of substrate induction of conjugation and plasmid transfer in any bacterium. More recently, I discovered a low molecular weight compound that is also required for conjugation. It is closely related to the autoinducer of bioluminescence in Vibrio fischeri. Nearly all of my work was done in collaboration with colleagues and graduate students.

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