Chemical Crosstalk between Bacteria and Plants – Agrobacterium Tumefaciens as a Model Pathogen

Shimrit David, Chemistry, Ben Gurion university , beer sheva, Israel
Aviad Mandabi, Chemistry, Ben Gurion university , beer sheva, Israel
Hagai Reiss, Chemistry, Ben Gurion university , beer sheva, Israel
Michael M. Meijler, Chemistry, Ben Gurion university , beer sheva, Israel

Quorum sensing (QS) is a mechanism by which bacteria can coordinate population wide gene expression and function as a single multicellular organism. In order to achieve this, bacteria secrete small diffusible signal molecules which allow them to "share information" and regulate gene expression that is of benefit to the whole community. Understanding quorum sensing (QS) mechanisms at the highest possible molecular detail is essential for solving challenges caused by bacterial virulence and biofilm formation.

The plant pathogen Agrobacterium tumefaciens is one of many gram negative soil bacteria that use QS to colonize plants. We chose to target QS in A. tumefaciens since it induces the formation of crown gall tumors at the wound sites on host plants, and its QS system is well defined. The infection occurs as a result of tumor- inducing (Ti) plasmid, injected by the bacteria in order to create conjugated system. It is known that A. tumefaciens uses its QS system to activate target genes on the Ti plasmid, and therefore attenuation of QS will enable us to control the infection process and this may help to prevent crown gall diseases on plants.

To accomplish this goal we performed a library screening of 3800 natural compounds in order to find potential agonists and antagonists. Several highly potent molecules were selected, and we currently synthesized a focused library of analogs around these hits. Using these tools, we aim to gain a significant advance in understanding the connection between QS mechanisms in A. tumefaciens and bacterial-plant interactions.