Chromogenic Catechol Substrates
These novel compounds, exemplified by the 3',4'-Dihydroxyflavone (DHF) derivatives such as DHF-galactoside (50045), DHF-glucoside (50059) and DHF-riboside (50180) offer several advantages over classic indoxyl substrates like X-Gal. Used in conjunction with an iron salt, bacteria which hydrolyse these new substrates produce discrete black or dark brown colonies on agar plates. These colours contrast with the blues and reds produced by most indoxyl substrates. Moreover, with the choice of appropriate substrates, DHF compounds may be used to mask the products of other enzyme activity indicators, including indoxyl substrates. When aluminium salts are used in place of iron salts, DHF compounds have the unique ability to furnish discrete yellow colonies.