Genetic and Evolutionary Analysis of Mutations in thegusAGene That Cause the Absence of β‐Glucuronidase Activity inEscherichia coliO157:H7
- 1 October 2001
- journal article
- research article
- Published by Oxford University Press (OUP) in The Journal of Infectious Diseases
- Vol. 184 (7) , 918-921
- https://doi.org/10.1086/323154
Abstract
Escherichia coli serotype O157:H7 do not exhibit β-glucuronidase (GUD) activity but carry the gusA gene (uidA) that encodes for GUD. In trans-complementation, the gusA gene cloned from the GUD-positive variant strain 493-89 effectively restored GUD activity in O157:H7 strain 35150. Comparison of gusA sequences from the GUD-negative 35150 strain to that of 493-89 revealed several base mutations, including a guanosine (G) dinucleotide insertion that caused a frameshift in the 35150 gusA gene and introduced a predicted premature termination codon. This explains the absence of GUD activity in O157:H7. A 35150 gusA construct from which the G-G insertion was deleted restored activity in GUD-negative O157:H7 transformants. The G-G insertion was present in all GUD-negative O157:H7 strains but was absent in their GUD-positive variants. The G-G insertion that produced the characteristic GUD-negative phenotype to O157:H7 strains appeared later than the other gusA mutations in the evolutionary emergence of O157:H7Keywords
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