Adhesion mechanisms of Vibrio fluvialis to skin mucus of Epinephelus awoara

Vibriofluvialis incubated in trypticase soy broth （TSB） showed stronger adhesion to the skin mucus of Epinephelus awoara than V. fluvialis grown on trypticase soy agar （TSA）, and this bacterial adhesion was assessed in terms of saturation kinetics. Treating bacteria with antibody against O-antigens resulted in significantly reduced bacterial adhesion. In the early growth stage, the adhering bacteria numbers increased with incubation time, peaked at 24 h, and then dropped sharply. Prior heat treatment of the mucus at various temperatures resulted in different effects on bacterial adhesion. No remarkable effect on bacterial adhesion was detected after treating mucus with protease K and trypsin, whereas periodic acid treatment significantly enhanced bacterial adhesion. Extracts of K fluvialis surface structures at high concentrations significantly inhibited bacterial adhesion, while relatively low concentrations enhanced adhesion. V. fluvialis had strong affinity for a high molecular weight mucus component. These results indicate that V.fluvialis adhered strongly to E. awoara mucus by specific adhesion and that this adhesion was influenced by many factors, including bacterial conditions, mucus, and the environment.

Functional C1q is present in the skin mucus of Siberian sturgeon (Acipenser baerii)

The skin mucus of fish acts as the first line of self-protection against pathogens in the aquatic environment and comprises a number of innate immune components.However,the presence of the critical classical complement component C1q,which links the innate and adaptive immune systems of mammalians,has not been explored in a primitive actinopterygian fish.In this study,we report that C1q is present in the skin mucus of the Siberian sturgeon(Acipenser baerii).The skin mucus was able to inhibit the growth of Escherichia coli.The bacteriostatic activity of the skin mucus was reduced by heating and by pre-incubation with EDTA or mouse anti-human C1q antibody.We also detected C1q protein in skin mucus using the western blot procedure and isolated a cDNA that encodes the Siberian sturgeon C1qC,which had 44.7–51.4%identity with C1qCs in teleosts and tetrapods.A phylogenetic analysis revealed that Siberian sturgeon C1qC lies at the root of the actinopterygian branch and is separate from the tetrapod branch.The C1qC transcript was expressed in many tissues as well as in skin.Our data indicate that C1q is present in the skin mucus of the Siberian sturgeon to protect against water-borne bacteria,and the C1qC found in the sturgeon may represent the primitive form of teleost and tetrapod C1qCs.