Bacterial messages to Eukaryotes

Symbiotic relationships involving microbes and eukaryotes come in many flavors as all eukaryotes have spent their entire evolutionary history on a planet teeming with microbes, and the two have evolved many ways of dealing with each other. This lecture will describe the small molecule chemistry that regulates a particularly complicated symbiotic relationship between bacteria belonging to the roseobacter clade and the microscopic alga Emiliana huxleyi and some of its relatives. The relationship is complicated because it changes with time as the bacterial chemistry responds to variable signals sent by their algal partner. The talk will involve three related topics, and the first is the isolation and structures of the bacterially produced roseobacticides, a group of roughly a dozen characterized molecules – and many more remaining to be characterized – with unusual structures as illustrated by roseobacticides A, B and C shown below.

The second topic is the biology involved in the symbiosis, especially the roles of the newly identified roseobacticides. The relationship between bacteria and alga changes from a mutualism to an antagonism as shown below, and the changing relationship is reflected in, and caused by, changes in bacterial metabolism

The third topic addresses how the bacteria biosynthesize roseobacticides from amino acid starting materials as outlined below.