An unknown protein reacted with anti-human IgA, namely, IgA-like protein, has been reported in shrimp, but information regarding its identification is not available. In the present study, an affinity proteomic strategy was applied to identify the IgA-like protein of shrimp Litopenaeus vannamei. The protein of 75 kDa was isolated and confirmed by affinity chromatography and Western blotting with goat anti-human IgA, respectively, and then identified as hemocyanin, a member of IgSF, by mass spectrometry. Moreover, our results showed that human IgA and L. vannamei hemocyanin could separately react with goat anti-human IgA or rabbit anti-shrimp affinity hemocyanin (a-hemocyanin). Further evidences indicated that the recombinant protein of the Ig-like conserved domain could react with anti-human IgA. Interestingly, our results indicated that L. vannamei hemocyanin could aggregate with eight species of shrimp pathogenic bacteria and four types of animal erythrocytes directly. These results indicate that L. vannamei hemocyanin, an IgA-like protein, has dual function of reaction with anti-human IgA as an antigen and of activity binding to bacteria and animal erythrocytes as an agglutinin, suggesting its characteristic role as an IgSF molecule. In addition, our approach suggests that affinity proteomics based on heterogeneous antibody can speed up the identification of Fossman antigens.

An agar-degrading bacterium, Catenovulum sp. X3, was isolated from the seawater of Shantou, China. A novel β-agarase gene agaXa was cloned from the strain Catenovulum sp. X3. The gene agaXa consists of 1,590 bp and encodes a protein of 529 amino acids, with only 40 % amino acid sequence identity with known agarases. AgaXa should belong to the glycoside hydrolase family GH118 based on the amino acid sequence similarity. The molecular mass of the recombinant AgaXa (rAgaXa) was estimated to be 52 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It had a maximal agarase activity at 52 °C and pH 7.4 and was stable over pH 5.0 ~ 9.0 and at temperatures below 42 °C. The K m and V max for agarose were 10.5 mg/ml and 588.2 U/mg, respectively. The purified rAgaXa showed endolytic activity on agarose degradation, yielding neoagarohexaose, neoagarooctaose, neoagarodecaose, and neoagarododecaose as the end products. The results showed that AgaXa has potential applications in agar degradation for the production of oligosaccharides with various bioactivities.

Aims:  Isolation and characterization of an agarase‐producing bacterium Agarivorans sp. HZ105. Methods and Results:  An agarase‐producing bacterium strain HZ105 had been isolated from marine sediment sample. Based on phylogenetic analysis of the 16S rRNA gene sequence and phenotypic analysis, as well as biochemical analyses, this strain was named Agarivorans sp. HZ105. Effect of pH, NaCl on the growth and agarase production of strain HZ105 was studied. Strain HZ105 produced three extracellular agarases which were purified to homogeneity from bands in the PAGE gel. Two agarases of these three had a molecular mass of 54, 58 kDa, respectively. And the MS and MS/MS spectra were used to identify the agarases. Conclusions:  The MS spectra result showed that the agarases of strain HZ105 should be beta‐agarase and belong to the family 50 of glycosyl hydrolases. The agarases could keep stable activity at room temperature. Significance and Impact of the Study:  The strain HZ105 was useful to produce stable agarases. The solution produced by agar’s degradation in the agar plates was first reported to be used for purification of agarase. Agarases were purified to homogeneity directly from the PAGE gel without stained by Coomassie brilliant blue.

A novel yellow-pigmented, agarolytic bacterial strain, designated ZC1 T , was isolated from the surface of the marine red alga Porphyra haitanensis collected near Nan Ao Island, Guangdong province, China. The isolate was Gram-stain-negative, strictly aerobic and rod-shaped and displayed b-galactosidase, alkaline phosphatase, catalase and oxidase activities. The predominant cellular fatty acids were iso-C 15 : 0 , summed feature 3 (comprising C 16 : 1 v7c and/or iso-C 15 : 0 2-OH) and iso-C 17 : 0 3-OH. The major menaquinone was menaquinone 6 (MK-6). The DNA G+C content was 32.8 mol%. Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain ZC1T was closely related to members of the genus Aquimarina in the family Flavobacteriaceae, phylum Bacteroidetes. Based on phylogenetic and phenotypic evidence, strain ZC1 T (5CCTCC AB 2010229 T 5NBRC 107695 T ) represents the type strain of a novel species in the genus Aquimarina, for which the name Aquimarina agarilytica sp. nov. is proposed.The genus Aquimarina (family Flavobacteriaceae, phylum In the course of a screening of marine environments for agardegrading bacteria, a yellow-pigmented bacterium, designated strain ZC1 T , was isolated from the surface of a red alga (Porphyra haitanensis) collected from shallow water near the coast of Nan Ao Island, located on the Tropic of Cancer, at 117 u E, near the city of Shantou in Guangdong province, in south-eastern China. The red alga was crushed in a mortar with sterile seawater and spread on plates of marine agar (MA) consisting of 1.5 % agar, 0.5 % tryptone (Oxoid) and 0.1 % yeast extract (Oxoid) in artificial seawater containing (w/v) 2.5 % NaCl, 0.63 % MgSO 4 . 7H 2 O, 0.46 % MgCl 2 . 6H 2 O, 0.1 % CaCl 2 and 0.07 % KCl. The plates were incubated at 25 u C for 3 days under aerobic conditions. Strain ZC1 T , which formed colonies that sank into the agar and were each surrounded by a clear halo of liquid, was purified by successive streaking on MA. The purified strain was preserved at 280 u C in marine broth (MB) containing 15 % (v/v) glycerol.For DNA extraction, strain ZC1T was cultivated aerobically in MB supplemented with 0