'Childless' bacteria make better workers

14 June 2002

Preventing microbes from reproducing is a new concept that has the potential to manufacture large quantities of important pharmaceutical proteins, according to an article in the May issue of Microbiology Today magazine from the Society for General Microbiology.

"Reproduction is a serious distraction from other activities for all forms of life," says author Dr David Summers, of Cambridge University. "We've developed a method to trap E. coli cells in a pre-divisional stage. This energy-saving tactic allows the bacteria to concentrate their resources on producing specialised products including recombinant proteins such as antibody fragments and cytokines."

E. coli have been put to work in bacterial cell factories for many years because they are cheap and easy to grow. But the fact that they double in number every twenty minutes has always been a limiting factor in product yield.

"Our quiescent cell protein expression system (Q-cells) relies on the over-production of a small RNA molecule called Rcd. The action of Rcd blocks chromosomal genes but allows the expression of plasmid genes - small circular pieces of DNA - to continue," explains Dr Summers. "When we looked at Q-cells under the microscope we found that the bacterial chromosome was highly condensed. This is similar to the formation of heterochromatin, which blocks gene expression in eukaryotes."

"By transplanting protein genes onto plasmids we are exploring the potential of Q-cells to manufacture a variety of recombinant proteins. Under the direction of BTG plc, who hold the patents for this technology, we are now looking at ways to scale-up this system to an industrial level," says Dr Summers.

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