Antibacterial proteins in the serum hemolymph and hemocyte lysate supernatant of the banana prawn, penaeus merguiensis

Abstract

As invertebrates do not synthesize specific antibodies, a number of antibacterial proteins and lectins have been isolated from their serum hemolymph and hemocytes. Antibacterial activity in serum hemolymph and hemocyte lysate supernatant (HLS) of the banana prawn, Penaeus merguiensis was investtigateg in vitro. The marine bacterium, Vibrio spp., Escherichia coli and Staphylococcus aureus were used as the test organisms. Hemocytes from P. merguiensis are classified into three main populations: hyaline, small-granular and large-granular under light microscope like other crustaceans. Hyaline cell refers to hemocytes that their cells contain no cytoplasmic granules, whereas granulocytes (small-granular and large-granular) contain abundant granules. Granulocytes and hyaline cells are present at 91 and 5 % of the circulating hemocytes, respectively. Proteins in serum hemolymph and HLS possess high antibacterial activity against Gram-negative bacteria. Antibacterial proteins are mainly located in serum and hemolymph. The serum hemolymph and HLS of banana prawn agglutinate erythrocytes of different vertebrate species. Lectin from hemolymph of banana prawn was isolated by affinity chromatography on mucin-CNBr-activated Sepharose 4B and gel filtration chromatography on Sephacryl S-200. The purified lectin strongly reduced the viable count of the test bacteria. These results show that one of the antibacterial proteins in the serum hemolymph and HLS from P. merguiensis is a lectin and involves in shrimp immune responses.