Marker counter-selective

Flanking counter-selectable markers Eliminates vector backbone Reduces transformation efficiency 23,24... 

Schweizer HP. 1992. Allelic exchange in Pseudomonas aeruginosa using novel ColEl-type vectors and a family of cassettes containing a portable oriT and the counter-selectable Bacillus subtilis sacB marker. Mol Microbiol 6 1195-204. 

In addition, NR is a very convenient genetic marker, that has the potential to be selected or counter-selected in many organisms, whether they be plants (Caboche Rouze, 1990 Nussaume et al., 1991) or microorganisms (Unkles et al., 1989). NR-deficient (NR-) mutants will not grow on nitrate, but unlike wild-type organisms will not be killed by chlorate, a nitrate analogue that is toxic when reduced by NR. 

Figure 1 The classic yeast two-hybrid method and derivatives, (a) Schematic diagram of the yeast two-hybrid approach, describing an interaction between protein X and protein Y. Protein X is fused to a transcription factor DNA-binding domain (the "bait" construct), and protein Y is fused to a transcription factor activation domain (the "prey" construct), (b) High-throughput applications of the yeast two-hybrid method use mating of haploid strains carrying bait and prey, respectively. Hybrids can be mated in arrayed formats (as shown) or as libraries, (c) The reverse two-hybrid method uses a counter-selectable marker to indicate loss of protein interaction because of disruption by an inhibitor protein/small molecule ("/" illustrated in the diagram) or mutation(s) in proteins X and/or Y.

Zhang, X.Z. et al (2006) mazF, a novel counter-selectable marker for unmarked chromosomal manipulation in Bacillus subtilis. Nucleic Acids Res., 34 (9), e71. 

Heap, J.T., Ehsaan, M., Cooksley, C.M., Ng, Y.-K. et al (2012) Integration of DNA into bacterial chromosomes from plasmids without a counter-selection marker. Nucleic Acids Res., 40, e59. 

Electrochemical detection is based on a cell comprising a working electrode, where the sensing takes place and a counter reference electrode should maintain a stable potential (Rackus et al., 2015 Mir et al., 2009). The implementation of electrochanical detection systems in microdevices typically requires specific markers to promote a selective binding and detection. This biomolecular recognition takes place close to the functionalized surface of an electrode. For this reason, the electrode shape, dimension. 

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