Thalassiosira weissflogii grown in various Zn levels shows different ecophysiological responses to seawater acidification.

The presence of zinc (Zn), a vital element for algal physiological functions, coupled with the silicification of diatoms implies that it plays an integral role in the carbon and silicon cycles of the sea. In this study, we examined the effects of different pCO2 and Zn levels on growth rate, elemental compositions and silicification by Thalassiosira weissflogii. The results showed that under normal pCO2 (400 µatm), cultures of T. weissflogii were depressed for growth rate and silica incorporation rate, but encouraged for cellular silicon content, Si/C, Si/N, and sinking rate when Zn deficient (0.3 pmol L-1). However, cellular silicon and sinking rate of Zn-deficient and Zn-replete (25 pmol L-1) T. weissflogii were decreased and increased at higher pCO2 (800 µatm), respectively. Thus, acidification may affect diatoms significantly differently depending on the Zn levels of the ocean and then alter the biochemical cycling of carbon and silica.

Alterations in the Iron Homeostasis Network of Hepatocytes Caused by Hepatitis B Virus.

BACKGROUND: It is unclear whether hepatitis B virus (HBV) itself causes iron metabolism disorder in patients with chronic hepatitis B (CHB). In this study, we investigated the effect of HBV on iron metabolism at the clinical and cellular levels to determine the pathogenesis of CHB. MATERIALS: We enrolled 41 CHB patients and 20 healthy controls (HCs) in a retrospective study. Parameters of iron status included serum iron (SI), ferritin (SF), transferrin (TRF), soluble transferrin receptor (sTfR), transferrin saturation (TS), total iron-binding capacity (TIBC), unsaturated iron-binding capacity (UIBC), and hepcidin. Liver function indicators included serum alanine transaminase (ALT) and albumin. Furthermore, we investigated the correlations between iron markers and liver function indicators. Finally, the alterations in SF, TRF, transferrin receptor (TfR), and hepcidin expression were detected by RT-PCR, western blot, and cell immunofluorescence after HepG2 cells and Huh7 cells were transfected with the pSM2-HBV plasmid. We also measured these alterations between HepG2 cells and HepG2.215 cells. The significance of differences was analyzed by SPSS version 17.0. RESULTS: Compared with healthy controls, the CHB patients were more likely to have lower levels of serum hepcidin, TRF, sTfR, TIBC, and UIBC and higher levels of SI, SF, and TS (p < 0.05, all). In CHB patients, the levels of SI and SF correlated positively with ALT concentrations, and the serum hepcidin concentrations correlated positively with albumin concentrations (p < 0.05, all). The expression levels of ferritin, transferrin, and hepcidin mRNA and protein were significantly higher in HepG2.215 cells than in HepG2 cells, while expression levels of TfR were lower. The alterations in these iron markers in HepG2 and Huh7 cells that were transfected with pSM2-HBV plasmid were consistent with those in HepG2.215 cells. CONCLUSIONS: Serum iron markers tended to be abnormal in CHB patients. In hepatocytes, HBV promoted the expression of ferritin, transferrin, and hepcidin, while it inhibited the expression of TfR.

Identification of genes preferentially expressed by highly virulent piscine Streptococcus agalactiae upon interaction with macrophages.

Streptococcus agalactiae, long recognized as a mammalian pathogen, is an emerging concern with regard to fish. In this study, we used a mouse model and in vitro cell infection to evaluate the pathogenetic characteristics of S. agalactiae GD201008-001, isolated from tilapia in China. This bacterium was found to be highly virulent and capable of inducing brain damage by migrating into the brain by crossing the blood-brain barrier (BBB). The phagocytosis assays indicated that this bacterium could be internalized by murine macrophages and survive intracellularly for more than 24 h, inducing injury to macrophages. Further, selective capture of transcribed sequences (SCOTS) was used to investigate microbial gene expression associated with intracellular survival. This positive cDNA selection technique identified 60 distinct genes that could be characterized into 6 functional categories. More than 50% of the differentially expressed genes were involved in metabolic adaptation. Some genes have previously been described as associated with virulence in other bacteria, and four showed no significant similarities to any other previously described genes. This study constitutes the first step in further gene expression analyses that will lead to a better understanding of the molecular mechanisms used by S. agalactiae to survive in macrophages and to cross the BBB.