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ARS Home » Southeast Area » Auburn, Alabama » Aquatic Animal Health Research » Research » Publications at this Location » Publication #213787
Title: Identification and characterization of an intervening sequence within the 23S ribosomal RNA genes of Edwardsiella ictaluri

Author
item ZHANG, YENFENG - AUBURN UNIVERSITY STUDENT
item ARIAS, C. - AUBURN UNIVERSITY

Submitted to: Aquaculture Miscellaneous Publications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2007
Publication Date: 6/30/2007
Citation: Zhang, Y., Arias, C.R. 2007. Identification and characterization of an intervening sequence within the 23S ribosomal RNA genes of Edwardsiella ictaluri. Systemic and Applied Microbiology 30: 93-101.

Interpretive Summary: Edwardsiella ictaluri, the cause of enteric septicemia in channel catfish (ESC) ranks as the preeminent cause of bacterial disease and mortality in the commercial channel catfish industry. Since pathogenic bacteria such as E. ictaluri exist as populations, the members of which exhibit varying degrees of virulence, sequence diversity within the 23S ribosomal RNA genes could provide important insights into the origins and spread of bacterial isolates within a biotope. The 16S and 23S ribosomal sequences have been used extensively in genotypic polymorphism analysis (genomovar grouping) within a distinct genospecies. Our studies for the first time characterize a unique intervening sequence region within the 23S ribosomal RNA genes of Edwardsiella ictaluri which will be useful in epidemiological studies and provide a better understanding of the complex stochastic events that coordinately interact to produce bacterial genotypic and consequent phenotypic diversity.

Technical Abstract: Comparison of the 23S rRNA gene sequences of Edwardsiella tarda and Edwardsiella ictaluri confirmed a close phylogenetic relationship between these two fish pathogen species and a distant relation with the 'core' members of the Enterobacteriaceae family. Analysis of the rrl gene for 23S rRNA in E. ictaluri revealed the presence of an intervening sequence (IVS) in helix-45. This new 98 bp IVS shared 97% nucleotide identity with Salmonella typhimurium helix-45 IVS. E. ictaluri helix-45 IVS was present in all E. ictaluri strains analyzed and in at least six rrl operons within each cell. Fragmentation of 23S rRNA due to IVS excision by RNase III was observed by methylene blue staining of ribosomal RNA extracted from E. ictaluri isolates. This is the first report of an IVS in the 23S rRNA gene of the genus Edwardsiella.