Yeast and LacZ, together. The first one is probably the first model organism: some thousand years ago, a woman has been the first biotechnologist (employing yeast she made the bread), so the referee tried to make some bread in vitro (he got the beer), then other researchers tried to exploit Saccharomices Cerevisiae but only minor applications like two-hybrid assay were reported.
Also the product of the gene LacZ (beta-galactosidase) is still ubiquitous in research, but (it seems) it doesn't work very well with yeast. Now, de Almeida and colleagues from Manchester University claims on Yeast 2008; 25: 71-76 a cell-based quantitative lacZ assay compatible for high-throughput screening. They optimized a procedure just marketed by Promega (Beta-Glo) and Applied Biosystems (Galacto-Lightplus); briefly, the substrate Xgal is substituted by so-called 6-O-beta-galactopyranosyl-luciferin. Such molecule, is cleaved by beta-gal and release D-luciferin. Luciferin, in presence of ATP is oxidized by another reporter (firefly luciferase) and shed light. Results: three order of magnitude and less than 100 yeast cells visualized. Suggested for lazy people that doesn't want to change such fuddy-duddy lacZ with a brighter stand-alone luciferase.
de Almeida, R.A., Burgess, D., Shema, R., Motlekar, N., Napper, A.D., Diamond, S.L., Pavitt, G.D. (2008). ASaccharomyces cerevisiae cell-based quantitative Î²-galactosidase assay compatible with robotic handling and high-throughput screening. Yeast, 25(1), 71-76. DOI: 10.1002/yea.1570