MISSISSIPPI STATE – The best way to battle a pathogen affecting the state’s catfish industry is to know as much about it as possible, and Mississippi State University researchers took a major step in that direction this summer.

Researchers at MSU’s College of Veterinary Medicine released the genome sequence of Edwardsiella ictaluri 93-146, the most important pathogen affecting the state’s channel catfish aquaculture industry. Dr. Mark Lawrence, a CVM professor of basic sciences, was the lead investigator of the project, which was completed this summer.

“Mississippi has more than half of the country’s catfish aquaculture production, so it is only fitting that MSU lead the effort to sequence this pathogen,” Lawrence said. “Catfish is the nation’s largest aquaculture industry, both in terms of acres and dollar value.”

A genome is the complete genetic material of a living organism. To map the genome sequence of Edwardsiella ictaluri, the research team determined the exact order of more than 3.8 million DNA bases that make up its chromosome.

Once this data was collected and verified, almost 4,000 genes were identified and labeled. Then the sequence was officially released to GenBank, the world’s database for genetic sequencing information.

“Researchers around the world can now access this information to accelerate their research on development of new vaccines and treatments for the disease,” Lawrence said.

MSU collaborated on this genetic project primarily with researchers from the Laboratory for Genomics & Bioinformatics at the University of Oklahoma Health Sciences Center. The Louisiana State University School of Veterinary Medicine was also involved, and the work was funded through a U.S. Department of Agriculture grant.

“Edwardsiella ictaluri is the causative agent of enteric septicemia of catfish, or ESC,” Lawrence said. “This is a significant disease of farm-raised catfish. The acute form of ESC causes bacterial septicemia, which rapidly leads to death. The chronic form of this disease causes a characteristic head lesion that also may proceed to septicemia and death.”

ESC only occurs in channel catfish, and according to a 2003 report from the USDA Animal and Plant Health Inspection Service, ESC is the most prevalent disease affecting the channel catfish aquaculture industry.

“Because E. ictaluri isolates from ESC outbreaks are all the same serotype, it is considered a good candidate for the development of a vaccine,” Lawrence said.

In addition to accelerating vaccine research against ESC, Lawrence said the Edwardsiella ictaluri genome sequence will also be compared to the genomes of other bacterial pathogens.

“Edwardsiella ictaluri is actually closely related to bacterial pathogens that cause disease in humans, such as E. coli and Salmonella,” Lawrence said. “It is also closely related to Yersinia, which causes bubonic plague. Comparison of the Edwardsiella genome to the genomes of these human pathogens may provide clues on how bacteria adapt to warm-blooded and cold-blooded hosts.”

Dr. Stephen Pruett, head of CVM’s Department of Basic Sciences, said this was a major accomplishment for Lawrence and his research team.

“It helps us fulfill our obligation not only to the scientific community, but to the people of Mississippi to produce scientifically important and useful research results,” Pruett said. “It is especially gratifying that this work will very likely yield great benefits for catfish production, one of our leading agricultural industries.”

Contact: Dr. Mark Lawrence, (662) 325-1195