ABSTRACT
Objective To investigate the secondary metabolites of actinomycete Brevibacterium sp. associated with the sea cucumber Apostichopus japonicus Selenka. Methods The ethyl acetate extract of the actinomycete was purified by repeated column chromatography on silica gel, Sephadex LH-20, and high-performance liquid chromatography (HPLC) to obtain pure compounds; and the compound structures were elucidated by spectroscopic analysis (nuclear magnetic resonance, NMR; mass spectrometry, MS) and the results were compared with the previously reported data. Results Seven compounds were isolated: cyclo-(L-Pro-L-Phe) (1), cyclo-(L-Pro-L-Met) (2), cyclo-(L-Pro-L-Tyr) (3), cyclo-(L-Pro-L-Val) (4), cyclo-(L-Pro-L-Pro) (5), cyclo-(L-Val-Gly) (6), and cyclo-(L-Pro-L-Leu) (7). Conclusion This is the first report on the secondary metabolites of microorganisms associated with the sea cucumber Apostichopus japonicus Selenka, and all the seven compounds have been reported from the actinomycete Brevibacterium sp. for the first time.
ABSTRACT
A outbreak of disease with symptoms of evisceration and skin ulteration led to mass mortality in sea cucumber Apostichopus japonicus cultivated in indoor ponds near the Dalian coast from December 2004 to April 2005. Spherical virus particles with a diameter of 75-200 nm were found in the cytoplasm of cells in the water-system, the alimentary canal and in the respiratory trees of the diseased and dying sea cucumber individuals by electron microscopic observation of ultrathin sections. Examination by negative stained samples revealed that all the diseased sea cucumbers were infected by the virus, while the healthly ones cultivated outside the contagious area were not. Two bacterial strains were also isolated from the diseased animals. When exposed to a medium containing the virus particles, regardless of whether the bacterial suspension was added,healthy sea cucumbers exhibited identical disease symptoms as the ones in the indoor ponds, and had a mortality of 90%-100%. However, when exposed to a medium in which there was only one of the two bacterial strains, 30%-80% of the sea cucumbers were infected and nearly 20% died. Negative staining showed that the viral particles were detected only in the bodies of the tested animals that were exposed to the viral medium. Histopathologically, the diseased sea cucumbers are characterized by karyopycnosis, and disintegration of the endoplasmic reticula and mitochondria in the epithelial cells in the water-system, the respiratory tree and the alimentary canal.
ABSTRACT
Objective:To study the effects of different molecular weight of collagen polypeptides from Apostichopus japonicus (A1:6 000U