Purification and characterization of a 630 kDa bacterial killing metalloprotease (KilC) isolated from plaice Pleuronectes platessa (L.), epidermal mucus

Smelling danger - alarm cue responses in the polychaete Nereis (Hediste) diversicolor (Müller, 1776) to potential fish predation

The harbour ragworm, Nereis (Hediste) diversicolor is a common intertidal marine polychaete that lives in burrows from which it has to partially emerge in order to forage. In doing so, it is exposed to a variety of predators. One way in which predation risk can be minimised is through chemical detection from within the relative safety of the burrows. Using CCTV and motion capture software, we show that H. diversicolor is able to detect chemical cues associated with the presence of juvenile flounder (Platichthys flesus). Number of emergences, emergence duration and distance from burrow entrance are all significantly reduced during exposure to flounder conditioned seawater and flounder mucous spiked seawater above a threshold with no evidence of behavioural habituation. Mucous from bottom-dwelling juvenile plaice (Pleuronectes platessa) and pelagic adult herring (Clupea harengus) elicit similar responses, suggesting that the behavioural reactions are species independent. The data implies that H. diversicolor must have well developed chemosensory mechanisms for predator detection and is consequently able to effectively minimize risk.

Isolation and cDNA cloning of an antibacterial L-amino acid oxidase from the skin mucus of the great sculpin Myoxocephalus polyacanthocephalus

The skin mucus of the great sculpin Myoxocephalus polyacanthocephalus showed both antibacterial and L-amino acid oxidase (LAO) activities. Antibacterial LAOs were purified from the skin mucus of the M. polyacanthocephalus by column chromatography and named MPLAO1, MPLAO2, and MPLAO3, based on the order of elution by ion-exchange high performance liquid chromatography. cDNA cloning of MPLAO3 revealed that the full-length cDNAwas 2659 bp and encoded the signal peptide (Met1-Ala26) and the mature protein (Val28-Phe520). A homology search using the BLAST program revealed that MPLAO3 shared sequence identity with LAO family proteins, and had 74% identity with the antibacterial LAO from the skin mucus of the rockfish Sebastes schlegeli. MPLAO3 catalyzed the oxidation of only L-lysine with a Km of 0.16 mM. MPLAO3 exhibited potent antibacterial activity against both Gram-positive and Gramnegative bacteria, and was most active against Aeromonas salmonicida JCM7874 with a minimum inhibitory concentration of 0.02 microg/mL. The antibacterial activity was attributable to H2O2, because the activity was completely lost in the presence of catalase. The antibacterial LAOs may be involved in the innate immunity of the great sculpin M. polyacanthocephalus skin.