We have designed a bacterial system that is switched between different states by red light. The system consists of a synthetic sensor kinase that allows a lawn of bacteria to function as a biological film, such that the projection of a pattern of light on to the bacteria produces a high-definition (about 100 megapixels per square inch), two-dimensional chemical image. This spatial control of bacterial gene expression could be used to 'print' complex biological materials, for example, and to investigate signalling pathways through precise spatial and temporal control of their phosphorylation steps.

RT-PCR analysis of isolated DNA from ChIP using primers for two representative high-affinity sites (gray) and two low-affinity sites (white) in the mouse genome. Mouse major satellite DNA (black) was used as a positive control for the high-affinity site. Each bar represents SEM; n = 3 or 4; *P < 0.05 by one-way ANOVA followed by Student's t test.

We have used RNA aptamer:gelonin conjugates to target and specifically destroy cells overexpressing the known cancer biomarker prostate-specific membrane antigen (PSMA). Aptamer:toxin conjugates have an IC 50 of 27 nmol/L and display an increased potency of at least 600-fold relative to cells that do not express PSMA. The aptamer not only promotes uptake into target cells but also decreases the toxicity of gelonin in non-target cells. These results validate the notion that ''escort aptamers'' may be useful for the treatment of specific tumors expressing unique antigen targets. (Cancer Res 2006; 66(12): 5989-92)

Highlights d Most mouse Cre driver lines tested exhibited variable rates of germline recombination d Germline recombination exhibits parental sex bias and target locus selectivity d Similar principles apply to multiple organisms and recombinase systems d Guidelines are provided for detecting and minimizing unwanted germline recombination