title: Use of 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside for the isolation of beta-galactosidase-positive bacteria from municipal water supplies.
abstract: A new medium, mX-Gal, has been developed for the membrane filter enumeration of beta-galactosidase-positive bacteria in municipal water supplies. mX-Gal medium contains the chromogenic beta-galactosidase substrate 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal). All Aeromonas, Citrobacter, and Enterobacter strains isolated from raw water on mX-Gal medium were beta-galactosidase positive. In contrast, only 10 to 20% of these strains produced a red colony with a metallic sheen on m-Endo agar LES medium. Of 674 chlorinated water samples analyzed for total coliforms on m-Endo agar LES medium and for beta-galactosidase-positive bacteria on mX-Gal medium, 18 that were negative for coliforms on m-Endo agar LES showed beta-galactosidase-positive bacteria on mX-Gal. Of a total of 50 beta-galactosidase-positive bacteria isolated from these samples, 76% were identified as Aeromonas hydrophila.
authors.affiliation: Ontario Ministry of the Environment and Energy, 133 Dalton Avenue, Kingston, ON K7L 4X6, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Ley
authors.forename: S
authors.initials: S
authors.lastname: Barr
authors.forename: D
authors.initials: D
authors.lastname: Fredenburgh
authors.forename: M
authors.initials: M
authors.lastname: Taylor
authors.forename: N
authors.initials: N
authors.lastname: Walker
mesh_terms: D000333:Aeromonas / Q000201:enzymology / Q000302:isolation & purification*; D002954:Citrobacter / Q000201:enzymology / Q000302:isolation & purification; D004754:Enterobacter / Q000201:enzymology / Q000302:isolation & purification; D004755:Enterobacteriaceae / Q000201:enzymology / Q000302:isolation & purification*; D005697:Galactosides; D007211:Indoles; D014871:Water Microbiology; D014881:Water Supply / Q000032:analysis*; D001616:beta-Galactosidase / Q000032:analysis
chemical_list: D005697:Galactosides; D007211:Indoles; D001616:beta-Galactosidase; C044888:5-bromo-4-chloro-3-indolyl beta-galactoside