Circular molecule splits bacteria

Uneven distribution of a tiny circular molecule is responsible for directing single-celled bacteria to split into two functionally and structurally different cells.

Scientists from the University of Washington and Stanford University developed a biosensor to monitor the concentration of cyclic diguanosine monophosphate – c-di-GMP – during cell division.

C-di-GMP acts as an internal messenger to tell bacteria like Pseudomonas aeruginosa and Caulobacter crescentus to split into a mother cell capable of clinging to surfaces and a daughter cell with a propeller to aid swimming.

The biosensor was based on genetically encoded fluorescence resonance energy transfer and measured changes in fluorescent emissions from the bacteria cells. They found emissions drop when the biosensor was bound to c-di-GMP and that c-di-GMP levels were five times higher in the non-motile, mother stalk cells.

“In both organisms, c-di-GMP levels were always significantly lower in the flagellated cell than the non-flagellated cell,” the researchers, including Dr Samuel Miller and Dr Matthias Christen, noted in their report published in Science.

The scientists believe this asymmetrical distribution occurs in other types of bacteria. Place-bound enzymes are thought to be responsible for an unequal distribution of c-di-GMP, and bacteria with more of these enzymes in flagellated cells are also higher in concentration. This suggests a localised drop in enzyme activity leads to a localised drop in c-di-GMP.

They believe that c-di-GMP exerts control over several biological functions inside the cell by linking up with proteins required to build and drive moving cells and riboswitches which can alter gene activity. It is implicated in several bacterial survival mechanisms, and is thought to regulate antibiotic resistance, adhesiveness and biofilm formation.