From insulin to washing powder: why understanding soil bacteria matters

Researchers have developed a new cell-free system to test DNA constructs designed to work in an industrially and medically important soil bacteria.

The research team, based in the Department of Medicine and the Centre for Synthetic Biology and Innovation, recently published their findings in Metabolic Engineering. 

We spoke to lead author Dr Richard Kelwick to unpick the broader signficiance of the study.

Why are soil bacteria important?

The soil bacterium Bacillus subtilis is generally regarded as safe (GRAS) by the U.S. Food and Drug Administration (FDA) and is used in industry and medicine to manufacture a broad range of useful things such as insulin, washing powder enzymes and many other proteins, drugs and molecules.

Our lives are therefore positively impacted by improvements in the technologies used to enhance our understanding of Bacillus subtilis, and our ability to enhance the manufacture of drugs, materials and medicines in either living Bacillus subtilis bacteria or Bacillus subtilis cell-free systems.

What are cell-free transcription-translation systems? 

These are systems in which we combine a cellular extract with an energy mix, to which we can add an engineered DNA (called a plasmid) for testing.

Our scientific paper describes the methods we used to improve the activity of Bacillus subtilis cell-free transcription-translation systems. We also describe how our improved systems are easier to make than those previously described in earlier publications.

What are the benefits?

Because the Bacillus subtilis cellular extract and energy mix contains all of the components needed for both transcription (DNA-to-mRNA) and translation (mRNA-to-protein), it means that we can make proteins from DNA in vitro (in a test tube) without needing to work with living cells.

Our system makes it easier and quicker to test new DNA constructs that are designed to work specifically in Bacillus subtilis.

What else can we use these systems for?

Our cell-free systems are useful to a wide range of research projects and questions.

We used our improved cell-free transcription-translation systems to test Bacillus subtilis DNA regulatory elements (the bits of DNA that control gene expression) in vitro, and to show that what we learn in vitro is comparable to how they behave in vivo (in living cells).

We have also applied these new systems to show that we can test simple genetic circuits, as well as to produce and test a functional enzyme.

Acknowledgements

We wish to acknowledge the support of the Engineering and Physical Science Research Council (EPSRC) – [EP/K034359/1; EP/J02175X/1] and that of our colleagues in the Centre for Synthetic Biology and Innovation (CSynBI) at Imperial College. We would also like to thank colleagues from The Flowers Consortium, particularly Professor Colin Harwood, for their support and advice. We also thank Professor Angelika Gründling for the kind gift of Bacillus subtilis 168.