Identification of genomic differences between Escherichia Colistrains pathogenic for poultry and E. Coli K-12 MG1655
Abstract
Diseases of poultry caused by Escherichia coli result in significant economic
losses every year. Specific virulence factors associated with E. coli strains pathogenic
for poultry have been identified, but it is likely that others remain to be identified. The
objective of this project was to identify novel virulence factors of avian E. coli. The
signature-tagged mutagenesis technique was to be used for this purpose. Difficulties
were encountered using that technique, and it was decided that suppression subtractive
hybridization should be used to identify genomic differences between E. coli K-12 and
avian E. coli pathogenic for poultry. A total of 62 fragments specific to two avian
strains were identified. They were composed of sequences with homology to four types
of fragments: plasmid sequences, phage sequences, sequences with known function and
sequences without any currently known function. Two E. coli collections, a reference
collection of diverse strains (ECOR) and a collection of 41 avian isolates, were screened
for the presence of 25 of the 62 fragments. Eleven fragments were present in
significantly more of the avian strains than of the ECOR strains. Some of the fragments
were further characterized by sequencing the DNA flanking the fragments, and
analyzing the sequences for the putative genes. One of the fragments was disrupted in
the genome of an avian E. coli strain. The disruption mutant did not have reduced
virulence in two animal models tested, which indicates that the disrupted gene may not
be required for virulence. The role of the other fragment sequences in the virulence of
avian E. coli has not yet been determined.