title: Proteomic characterization of the interactions between fish serum proteins and waterborne bacteria reveals the suppression of anti-oxidative defense as a serum-mediated antimicrobial mechanism.
abstract: Fish blood is one of the crucial tissues of innate immune system, but the full repertoire of fish serum components involved in antibacterial defense is not fully identified. In this study, we demonstrated that turbot serum, but not the heat-inactivated control, significantly reduced the number of Edwardsiella tarda (E. tarda). By conjugating serum proteins with fluorescent dyes, we showed that E. tarda were coated with multiple fish proteins. In order to identify these proteins, we used E. tarda to capture turbot serum proteins and subjected the samples to shotgun proteomic analysis. A total of 76 fish proteins were identified in high confidence, including known antimicrobial proteins such as immunoglobins and complement components. 34 proteins with no previously known immunological functions were also identified. The expression of one of these proteins, IQ motif containing H (IQCH), was exclusively in fish brain and gonads and was induced during bacterial infection. This approach also allowed the study of the corresponding proteomic changes in E. tarda exposed to turbot serum, which is a general decrease of bacterial protein expression except for an upregulation of membrane components after serum treatment. Interestingly, while most other known stresses stimulate bacterial antioxidant enzymes, fish serum induced a rapid suppression of antioxidant proteins and led to an accumulation of reactive oxygen species. Heat treatment of fish serum eliminated this effect, suggesting that heat labile factors in the fish serum overrode bacterial antioxidant defenses. Taken together, this work offers a comprehensive view of the interactions between fish serum proteins and bacteria, and reveals previously unknown factors and mechanisms in fish innate immunity.
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: Miao
authors.initials: M
authors.lastname: Dong
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: Yimin
authors.initials: Y
authors.lastname: Liang
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: Rajkumar
authors.initials: R
authors.lastname: Ramalingam
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: Sze Wing
authors.initials: SW
authors.lastname: Tang
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: Wei
authors.initials: W
authors.lastname: Shen
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: Rui
authors.initials: R
authors.lastname: Ye
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: Singaram
authors.initials: S
authors.lastname: Gopalakrishnan
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong. Electronic address: bhdwtau@cityu.edu.hk.
authors.forename: Doris Wai Ting
authors.initials: DWT
authors.lastname: Au
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong. Electronic address: yunwlam@cityu.edu.hk.
authors.forename: Yun Wah
authors.initials: YW
authors.lastname: Lam
mesh_terms: D016980:Aeromonas hydrophila / Q000502:physiology; D000818:Animals; D001798:Blood Proteins / Q000235:genetics* / Q000378:metabolism; D020609:Edwardsiella tarda / Q000502:physiology; D004756:Enterobacteriaceae Infections / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000662:veterinary; D005260:Female; D005393:Fish Diseases / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D005412:Flatfishes; D016905:Gram-Negative Bacterial Infections / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000662:veterinary; D008297:Male; D020543:Proteome; D014735:Vibrio Infections / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000662:veterinary; D044149:Vibrio alginolyticus / Q000502:physiology
chemical_list: D001798:Blood Proteins; D029941:Fish Proteins; D020543:Proteome
keywords: Antibacterial proteins; Antioxidant defence; Fish innate immunity; Quantitative proteomics; Waterborne pathogen