IN-SITU COLOR DETECTION OF ALPHA-L-ARABINOFURANOSIDASE, A NO-BACKGROUND REPORTER GENE, WITH 5-BROMO-3-INDOLYL-ALPHA-L-ARABINOFURANOSIDE

We describe the synthesis and use of 5-bromo-3-indolyl-alpha-L-arabino furanoside (5-BI-ara) for the detection of alpha-L-arabinofuranosidase in bacterial colonies. Since the product of 5-BI-ara hydrolysis is an intensely colored indigo precipitate, it is a useful substrate for in situ detection of alpha-L-arabinofuranosidase activity. Here we show that colonies of an Escherichia coli strain expressing a recombinant a lpha-L-arabinofuranosidase gene from Streptomyces lividans are readily identified by visual inspection on bacterial plates containing 5-BI-a ra. Use of 5-BI-ara should facilitate the detection of endogenous alph a-L-arabinofuranosidase activity in a variety of microorganisms. In ad dition, since alpha-L-arabinofuranosidase activity is not commonly fou nd in a large number of bacteria, yeast, and animal cells, 5-BI-ara wi ll be useful in exploring the use of genes coding for alpha-L-arabinof uranosidase as gene expression reporters in heterologous systems. (C) 1996 Academic Press, Inc.