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cueO encodes a periplasmic multicopper oxidase, which is known to be involved in copper homeostasis and protection against oxidative stress in Escherichia coli K12. Transcriptional profiling showed that expression of genes associated with motility was lowered in a cueO mutant while expression of genes associated with autoaggregation was elevated. Increased aggregation was correlated with increased expression of cell surface proteins antigen 43 and curli. Changes in gene expression caused by the deletion of cueO were essentially independent of SoxR and OxyR, the global regulators of oxidative stress response.

The sequence of two enterohaemorrhagic Escherichia coli (EHEC) O157:H7 strains reveals the possession of at least 16 fimbrial gene clusters, many of the chaperone/usher class. The first part of this study examined the distribution of these clusters in a selection of EHEC/EPEC (enteropathogenic E. coli) serotypes to determine if any were likely to be unique to E. coli O157:H7. Six of the clusters, as determined by the presence of amplified main subunit or usher gene sequences, were detected only in the E. coli O157 and O145 serotypes tested. With the exception of one serotype O103 strain that contained an lpf2 cluster, lpf sequences were only detected in E. coli O157 of the serotypes tested. Expression from each cluster was measured by the construction of chromosomally integrated lacZ promoter fusions and plasmid-based eGFP fusions in E. coli O157:H7. This analysis demonstrated that the majority (11/15) of main fimbrial subunit genes were not expressed under the majority of conditions tested in vitro. One of the clusters showing promoter activity, loc8, has a temperature expression optimum indicating a possible role outside the host. From the presence of pseudogenes in three of the clusters, the lack of FimH-like minor adhesins in the clusters and their limited expression in vitro, it would appear that E. coli O157:H7 has a limited repertoire of expressed functional fimbriae. This restricted selection of fimbriae may be important in bringing about the tropism E. coli O157:H7 demonstrates for the terminal rectum of cattle.