Colorimetric enumeration of Escherichia coli based on beta-glucuronidase activity.
A medium containing a chromogenic substrate was developed for the enumeration of Escherichia coli on the basis of beta-glucuronidase activity. In this medium there was an inverse linear relationship between the log initial E. coli concentration and the time taken for the color to reach a threshold optical density of 0.05. This relationship applied even when the E. coli population contained 5% beta-glucuronidase-negative cells. Incubation at 44 degrees C reduced the time taken for color development and allowed the procedure to be used in the presence of a competitive microflora that outnumbered the E. coli population by a factor of 10(4). Sodium lauryl sulfate as an additional selective agent gave no significant improvement. In the analysis of environmental water samples, the technique gave a good correlation with a standard cultural method. The procedure shows promise as a simple method for testing the compliance of environmental samples with microbiological criteria for E. coli.
Department of Microbiology, University of Surrey, Guildford, United Kingdom.
M R
MR
Adams
S M
SM
Grubb
A
A
Hamer
M N
MN
Clifford
D002863:Chromogenic Compounds; D015169:Colony Count, Microbial; D003124:Colorimetry; D004926:Escherichia coli / Q000201:enzymology / Q000302:isolation & purification*; D005069:Evaluation Studies as Topic; D005965:Glucuronates; D005966:Glucuronidase / Q000032:analysis*; D009596:Nitrophenols; D014871:Water Microbiology
D002863:Chromogenic Compounds; D005965:Glucuronates; D009596:Nitrophenols; C049288:p-nitrophenol glucuronide; D005966:Glucuronidase