S11T2S21 E. coli
X-glucuronide
ribosome
DNA
Non-Coliform Bacteria
beta-glucuronidase
uidA
X-glucuronide
Chromo agar
ribosome
DNA
E Coli.
Figure 1. Modeling the use of Chromo agar to identify E. coli. The uidA gene codes
for the beta-glucuronidase enzyme which cleaves the X-glucuronide molecule (Feng
et al., 1991). This enzyme is specific to E. coli allowing for precise identification the
bacteria. Beta-glucuronidase cleaves X-glucuronide which releases fluorescence and
therefore detects beta-glucuronidase activity (Alonso et al., 1996).
References
Feng, P., Lum, R., Chang, G. W. (1991). Identification of uidA gene sequences in beta-Dglucuronidase-negative Escherichia coli. Applied and environmental microbiology, 57(1),
320-323.
Alonso, J. L., Amoros, I., Chong, S. Garelick, H. (1996). Quantitative determination of Escherichia
coli in water using CHROMagar® E. coli. Journal of Microbiological Methods, 25(3), 309315.