Cell-Free Synthetic Biology
"In general terms, synthetic biology brings to mind using “BioBricks”, which are engineered genetic parts used to modify an organism, such as bacteria or yeast. The idea is to modify the organism to work to our advantage; for example, to eat sugar and produce biofuel — a pretty good tradeoff, considering the cost of gasoline and the cost of sugar. This is a top-down methodology: take an existing organism, modify it’s DNA, measure it’s behavior, and repeat the modification process until the desired “behavior” is measured.
Some synthetic biology research, however, doesn’t use traditional organisms at all. In fact, doesn’t even use “cells”. This might be called cell-free synthetic biology, or in vitro synthetic biology. This is a bottom-up approach: create the desired “behavior” from scratch. The idea has existed for some time;
a good summary is Synthetic biology projects in vitro, Anthony C. Forster and George M. Church, Genome Res. 17:1-6, 2007: “Many biopolymer syntheses are already better scaled up in cell-free systems, such as linear DNAs by oligo synthesis and PCR, unmodified RNAs by in vitro transcription, and peptide libraries by in vitro transcription/translation. And engineering flexibility is much greater in vitro, unshackled from cellular viability, complexity, and walls.” (http://88proof.com/synthetic_biology/blog/archives/84)