Cell death in a harmful algal bloom causing species Alexandrium tamarense upon an algicidal bacterium induction.

Harmful algal blooms occur throughout the world, destroying aquatic ecosystems and threatening human health. The culture supernatant of the marine algicidal bacteria DHQ25 was able to lysis dinoflagellate Alexandrium tamarense. Loss of photosynthetic pigments, accompanied by a decline in Photosystem II (PSII) photochemical efficiency (Fv/Fm), in A. tamarense was detected under bacterial supernatant stress. Transmission electron microscope analysis showed obvious morphological modifications of chloroplast dismantling as a part of the algicidal process. The PSII electron transport chain was seriously blocked, with its reaction center damaged. This damage was detected in a relative transcriptional level of psbA and psbD genes, which encode the D1 and D2 proteins in the PSII reaction center. And the block in the electron transport chain of PSII might generate excessive reactive oxygen species (ROS) which could destroy the membrane system and pigment synthesis and activated enzymic antioxidant systems including superoxide dismutase (SOD) and catalase (CAT). This study indicated that marine bacteria with indirect algicidal activity played an important role in the changes of photosynthetic process in a harmful algal bloom species.

Association of APC Expression with Its Promoter Methylation Status and the Prognosis of Hepatocellular Carcinoma.

OBJECTIVE: The present study was aimed to investigate the APC expression, its promoter methylation status, the expression of ß-Catenin, c-Myc and Cyclin D1 and further explore their prognostic value in Hepatocellular carcinoma (HCC). PATIENTS AND METHODS: Serum samples from 90 HCC patients and 27 healthy donors were collected in this study. The methylation-specific PCR (MSP) was performed to evaluate promoter methylation status of APC gene. RT-qPCR was used to detect the mRNA expression of APC, ß-Catenin, c-Myc and Cyclin D1, meanwhile the protein expression were analyzed by Western blot. RESULTS: The positive rate of APC gene methylation in HCC patients (46.67%) was higher than healthy donors (11.11%). APC gene exhibited marked hypermethylation in the patients of TNM III-IV stage when compared to the patients of TNM I-II stage , the methylation status of APC gene was correlated with tumor size and lymph node metastasis whereas the APC gene methylation showed no relationship with the patient's sex and age. APC methylation may be associated with APC expression level, APC expression in HCC cells is silenced by aberrant promoter hypermethylation. In HCC patients with methylated APC, the mRNA and protein expression of ß-Catenin, c-Myc and Cyclin D1 were higher than the unmethylated patient subgroup and healthy donors. CONCLUTIONS: The downregulation of APC in HCC samples was associated with promoter hypermethylation. APC methylation could be used as a novel diagnostic biomarker in HCC, which was associated with regulation of Wnt/ß-Catenin signal pathway.

[Advance in study on active protein and peptide produced by marine bacteria--a review].

Biological active resources are various and abundant in the ocean. With this realization, active proteins and peptides especially marine bacteria active proteins and peptides have attracted much attention recently. The achievements in the study of bioactivities of marine bacterial proteins and peptides were reviewed in this paper. Acquisition and potential applications of these marine bacteria active products were then proposed. Additionally, we focused on the prospective outline on the study of this field.

Effect of oxidative stress induced by Brevibacterium sp. BS01 on a HAB causing species--Alexandrium tamarense.

Harmful algal blooms occur all over the world, destroying aquatic ecosystems and threatening other organisms. The culture supernatant of the marine algicidal actinomycete BS01 was able to lysis dinoflagellate Alexandrium tamarense ATGD98-006. Physiological and biochemical responses to oxidative stress in A. tamarense were investigated to elucidate the mechanism involved in BS01 inhibition of algal growth. Transmission electron microscope analysis revealed that there were some chloroplast abnormalities in response to BS01 supernatant. The decrease in cellular-soluble protein content suggested that cell growth was greatly inhibited at high concentration of BS01 supernatant. The increase in the levels of reactive oxygen species (ROS) and malondialdehyde contents following exposure to BS01 supernatant indicated that algal cells suffered from oxidative damage. The content of pigment was significantly decreased after 12 h treatment, which indicated that the accumulation of ROS destroyed pigment synthesis. Moreover, the decrease of Fv/Fm ratio suggested that in the photosynthetic system, the dominant sites producing ROS were destroyed by the supernatant of the BS01 culture. The activities of the antioxidant enzymes including superoxide dismutase and peroxidase increased in a short time and decreased slightly with increasing exposure time. A real-time PCR assay showed changes in the transcript abundances of two photosynthetic genes, psbA and psbD. The results showed that BS01 supernatant reduced the expression of the psbA gene after 2 h exposure, but the expression of the psbD gene was increased at concentrations of 1.0 and 1.5%. Our results demonstrated that the expression of the psbA gene was inhibited by the BS01 supernatant, which might block the electron transport chain, significantly enhancing ROS level and excess activity of the antioxidant system. The accumulation of ROS destoryed pigment synthesis and membrane integrity, and inhibited or ultimately killed the algal cells.