Dr Josh Ramsay

Biomedical Sciences, Curtin University
Regulation of horizontal gene transfer through integrated molecular circuitry

Abstract: The symbiosis island (ICEMlSymR7A) of Mesorhizobium loti is a 502-kb integrative and conjugative DNA element that confers on its bacterial host the ability to form a N2-fixing symbiosis with Lotus legumes. It was first discovered through its ability to convert non-symbiotic M. loti to symbionts of Lotus in New Zealand soils. Mobile genetic elements such as ICEMlSymR7A have been indirectly favoured in evolution due to their ability to distribute advantageous genes horizontally through the gene pool. However their mobility functions likely come at a cost to the donor bacterium, therefore the initiation of transfer is often tightly regulated. In this seminar I will describe our characterisation of the elegant molecular circuitry that controls horizontal gene transfer of ICEMlSymR7A. This circuitry integrates regulatory inputs from quorum sensing, a bimodal anti-activation switch and programmed ribosomal frame-shifting to control the proportion of cells in a population that are induced for excision and conjugative transfer.

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