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C-type lectins (CTL) are a large group of pattern-recognition proteins and to play important roles in glycoprotein metabolism, multicellular integration, and immunity. Based on their overall domain structure, they can be classified as different groups that possess different physiological functions. A typical C-type lectin (named as Om Lec1) was identified from the fish, Onychostoma macrolepis , an important cultured fish in China. Open reading frame of Om Lec1 contains a 570 bp, encoding a protein of 189 amino acids that includes a signal peptide and a single carbohydrate-recognition domain. The phylogenetic analysis showed that Om Lec1 could be grouped with C-type lectin from other fish. Om Lec1 was expressed in all the tissues in our study, and the expression level was highest in liver. And its relative expression levels were significantly upregulated following infection with Aeromonas hydrophila. The recombinant Om Lec1 protein (r Om Lec1) could agglutinate some Gram-negative bacteria and Gram-positive bacteria in vitro in the presence of Ca2+, showing a typical Ca2+-dependent carbohydrate-binding protein. Furthermore, r Om Lec1 purified from E. coli BL21 (DE3), strongly bound to LPS and PGN, as well as all tested bacteria in a Ca2+-dependent manner. These results indicate that Om Lec1 plays a central role in the innate immune response and as a pattern recognition receptor that recognizes diverse pathogens among O. macrolepis. • A typical C-type lectin with a EPN/WND motif (Om Lec1) was identified and characterized from Onychostoma macrolepis. • The expression levels of Om Lec1 gene were significantly up-regulated after pathogen challenge. • Recombinant Om Lec1 can agglutinates various bacteria in vitro in the presence of Ca2+. • Recombinant Om Lec1 could bind some saccharides such as d -mannose, LPS and PGN. [ABSTRACT FROM AUTHOR]