Credit: © 2007 ACS

A team of scientists has developed a simple method for generating two-dimensional arrays of living bacteria, which could prove extremely useful for drug screening and for studies of population dynamics and ecosystem evolution. Until now, various methods have been proposed, but they have all had limitations owing to the small size and motility of bacteria.

The new technique, reported by Damien Baigl of the Université Paris Descartes, France, and colleagues1 enables a pattern of Escherichia coli to be printed onto an agarose surface in just a few seconds and over a large area (in the order of square centimetres). First, a monolayer of E. coli was adsorbed onto an agarose block to form an 'inkpad'. A stamp made from a polymer moulded with the desired pattern was then used to transfer bacteria from the inkpad to another agarose substrate. The bacteria continued to grow after being printed — perfectly preserving the original pattern — demonstrating that the process does not affect the physiological behaviour of the cells.

The technique can be varied to produce arrays with different periods and spot sizes — with very low concentrations of bacteria on the inkpad, it was possible to produce spots containing a single E. coli cell. Furthermore, the group envisage that their method could be extended to generate multistrain bacterial arrays, which will enable complex ecosystems to be constructed.