Characterization of the rrn operons in the channel catfish pathogen Edwardsiella ictaluri.
OBJECTIVE
To advance diagnostics and phylogenetics of Edwardsiella ictaluri by sequencing and characterizing its rrn operons.


RESULTS
The Edw. ictaluri rrn operons were identified from a 5-7 kbp insert lambda library and from Edw. ictaluri fosmid clones. We present the complete sequences and analysis of all eight Edw. ictaluri rrn operons and unique regions located upstream and downstream. Two rrn operons were located in tandem with 169 bp separating them, which is apparently a conserved feature between Edw. ictaluri and Edwardsiella tarda. I-CeuI enzyme digestion of Edw. ictaluri genomic DNA and analysis by pulsed field gel electrophoresis indicated that rrn operon number and chromosomal locations are conserved within the species Edw. ictaluri.


CONCLUSIONS
The rrn operons of Edw. ictaluri have similar structure and flanking regions compared with other members of the family Enterobacteriaceae; however, the presence of eight copies of the rrn operon makes Edw. ictaluri unique within the family.


CONCLUSIONS
This research clarifies previous phylogenetic analyses of Edw. ictaluri and provides support for the Edw. ictaluri genome sequencing project. In addition, we identified a unique feature of two rrn operons that shows potential for the development of a diagnostic PCR method.
Williams
M L
ML
College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA.
Waldbieser
G C
GC
Dyer
D W
DW
Gillaspy
A F
AF
Lawrence
M L
ML
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D020610:Edwardsiella ictaluri / Q000235:genetics*; D020609:Edwardsiella tarda / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field / Q000379:methods; D004756:Enterobacteriaceae Infections / Q000175:diagnosis; D005393:Fish Diseases / Q000175:diagnosis / Q000382:microbiology; D005398:Fisheries; D015698:Genomic Library; D007059:Ictaluridae / Q000382:microbiology*; D007218:Industrial Microbiology; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D012407:rRNA Operon / Q000235:genetics*
D017931:DNA Primers