Location: Aquatic Animal Health Research2011 Annual Report
1a. Objectives (from AD-416)
The objective of this cooperative research project is to discover and develop novel natural antimicrobial peptides that could be used to control fish diseases. This research project will allow USDA, Agricultural Research Service and Qingdao Agricultural University (QDAU) to implement cooperative research with a common goal to discover and develop novel natural antimicrobial peptides to control fish bacterial diseases. The fish pathogens to be investigated include but not limited to Edwardsiella ictaluri, Streptococcus iniae, and Flavobacterium columnare.
1b. Approach (from AD-416)
Antimicrobial peptides will be isolated through bioassay-guided fractionation that shows activity against important fish bacterial pathogens such as, but not limited to, Edwardsiella ictaluri, Streptococcus iniae, and Flavobacterium columnare. The source of antimicrobial peptides will be aquatic animals, such as bivalves, from which a novel antimicrobial peptides has been discovered by Qingdao Agricultural University. Bioactive crude protein extracts will be initially tested for antimicrobial activity against fish pathogens. Various fractionation techniques, including HPLC, will be used to separate, purify, and determine the active antimicrobial ingredient guided by antimicrobial bioassays.
3. Progress Report
The objective of this cooperative research project is to discover and develop novel natural antimicrobial peptides to control bacterial diseases in aquatic animals. Using quantitative polymerase chain reaction (PCR) technique, the relative transcriptional levels of seven channel catfish antimicrobial peptide (AMP) genes [NK-lysin type 1, NK-lysin type 2, NK-lysin type 3, bactericidal permeability-increasing protein (BPI), cathepsin D, hepcidin, and liver-expressed antimicrobial peptide 2 (LEAP2)] in response to acute infection of Edwardsiella (E.) ictaluri have been determined. Among all the AMPs that were significantly upregulated at different time points, hepcidin at 4-, 6-, and 12-h post infection was upregulated the most. In vitro growth studies revealed that the presence of synthetic hepcidin peptide at concentration of 80 uM or higher significantly inhibited the growth of E. ictaluri. One manuscript has been submitted to a journal for publication. The project is monitored through e-mails with cooperators for planning, implementing, discussion of research and analyzing data.