Bacteria synchronized for drug delivery

A synthetic genetic circuit that mimics the quorum-sensing systems used by bacterial populations to coordinate gene expression enables bacteria to deliver drugs to mouse tumours in repeated and synchronized cycles. See Letter p.81 There is growing interest in using bacteria as living therapeutics, although the complications due to host responses and long-term effectiveness remain to be established. Omar Din et al. have now engineered a quorum-sensing clock into a strain of Salmonella known to target solid tumours by releasing a tumour-targeting toxin. The clock drives periodic lyses of the bacterial colony, thereby controlling the bacterial population and ensuring sustained anti-tumour toxin delivery in a mouse cancer model. Although the system as it stands does not represent an effective cure, this work indicates that synthetic biology can be harnessed to achieve dynamic and sustained delivery of therapeutics in vivo.