Synthetic biology: old wine in new bottles with an emerging language that ranges from the sublime to the ridiculous?

The central aim of synthetic biology is to create and exploit biological processes that do not occur naturally. In many cases this will involve one or more steps in genetic engineering to create an organism that so far has not been found in nature. In contrast, systems biology aims to describe biological processes in their entirety, be it the complete genome of an organism, community or ecosystem, or the processes occurring in such biological systems. Systems biology adopts a top-down approach; in contrast, synthetic biology requires a bottom-up approach: first a problem is identified; data from many possible sources, including systems biology, can then be searched for possible solutions. The current thematic issue explores some of the applications of synthetic biology. While systems biology strives to provide a complete description of what is available naturally, synthetic biology exploits this information to design solutions to a specific problem. The study by Quirino and Beier nicely illustrates this principle. It is just one of the contributions to this thematic issue that originated from poster or lecture presentations during the 5th FEMS Congress of Microbiology held in Leipzig in July 2013. Our scope was limited by an unexpected paucity of contributions in Leipzig exploring exciting contributions being made across Europe, for example, to the use of synthetic biology to generate replacements for naturally synthesized antibiotics. Also in strikingly low abundance were presentations on small RNAs: their global occurrence; their roles in the regulation of gene expression; and their potential for medical exploitation as antisense RNA. We are therefore pleased to include the article by Philipps et al. ‘Expression of Porphyromonas gingivalis small RNA in response to hemin availability identified using microarray and RNA-seq analysis’. Genetic engineering is undoubtedly one of the cornerstones of synthetic biology, not least for the production of recombinant proteins in heterologous hosts. While yeast and Escherichia coli strains have dominated the recombinant protein production literature, there is also keen interest in exploiting the secretion potential of Gram-positive bacteria. Jørgensen, Vrang and Madsen present a classic example of how problems of growth inhibition due to excessive lactate accumulation by Lactococcus lactis can be alleviated by combining a novel cloning system with physical removal of lactate from the culture by electrodialysis. A proof-of-principle experiment is described in which a nuclease from Staphylococcus aureus was accumulated in the heterologous host to a concentration of 2.5 g L . Despite the paucity of presentations in Leipzig in some important areas of microbiology, an attempt has been made in this volume to illustrate not only the breadth of topics that currently fall under the synthetic or systems labels, but also to explore how they might be related. This introduction also alerts our broader readership to the merits and drawbacks associated with the inevitable jargon that each new subdiscipline generates.