Diversity and composition of sulfate- and sulfite-reducing prokaryotes as affected by marine-freshwater gradient and sulfate availability.

Sulfate- and sulfite-reducing prokaryotes (SSRP) communities play a key role in both sulfur and carbon cycles. In estuarine ecosystems, sulfate concentrations change with tides and could be limited in tidal freshwater reach or deep sediments. In a subtropical estuary of northern Taiwan in December 2007, we examined the compositional changes of SSRP communities. We examined three sites: from the lower estuarine brackish-water reach (site GR and mangrove vegetation site, GM) to the upper estuarine tidal freshwater reach (site HR), as well as from surface to a 50-cm depth. The partial sequence of sulfite reductase (dsrB) genes was used as a molecular marker of SSRP, linked to polymerase chain reaction and denaturing gradient gel electrophoresis (DGGE) techniques. SSRP communities of the DGGE profiles varied with sites according to one-way analyses of similarities (Global R = 0.69, P = 0.001). Using cluster analysis, the DGGE profile was found to show site-specific clusters and a distinct depth zonation (five, six, and two SSRP communities at the GM, GR, and HR sites, respectively). SSRP composition was highly correlated to the combination of salinity, reduced sulfur, and total organic carbon contents (BIO-ENV analysis, r ( s ) = 0.56). After analyzing a total of 35 dsrB sequences in the DGGE gel, six groups with 15 phylotypes were found, which were closely related to marine-freshwater gradient. Moreover, sequences neighboring sulfite-reducing prokaryotes were observed, in addition to those affiliated to sulfate-reducing prokaryotes. Four phylotypes harvested in HR resembled the genus Desulfitobacterium, a sulfite-reducing prokaryote, which failed to use sulfate as an electron acceptor and were active in freshwater and sulfate-limited habitat. The other five phylotypes in the HR reach belonged to the sulfate-reducing prokaryotes of the genera Desulfatiferula, Desulfosarcina, Desulfovibrio, and Desulfotomaculum, which appeared to tolerate low salinity and low sulfate supply. SSRP phylotypes at the mangrove-vegetated GM site (five phylotypes in two groups) were phylogenetically less diverse, when compared with those at the non-mangrove-vegetated GR site (three phylotypes in three groups) and the tidally influenced freshwater HR site (nine phylotypes in five groups). Phylotypes found at GR and GM were all affiliated to marine sulfate-reducing prokaryote strains of the genera Desulfofaba, Desulfobotulus, Desulfatiferula, Desulfosarcina, and Desulfotomaculum. Notably, a phylotype recorded in the surface sediment at GR resembled the genus Desulfobulbus, which was recorded from freshwater environment consisting of the freshwater input at GR during ebb tides.

Effects of semidiurnal tidal circulation on the distribution of holo- and meroplankton in a subtropical estuary.

We examined how tidal changes and which physical factors affected holo- and meroplankton assemblages in a subtropical estuary in Taiwan in February 1999. A factor analysis showed that during tidal flooding, the water mass properties changed from low salinity (5-16) and high particulate organic carbon (POC, 2.6-4.5 mg L(-1)) content to increasing salinity and high total suspended matter content (29.0-104.5 mg L(-1)). With a receding tide, the water became more saline again, and its velocity increased (from non-detectable to 0.67 m s(-1)). One-way ANOVA showed that the distributions of four dominant taxa were affected by the ebb tide and exhibited two distinct groups. The first group consisted of non-motile invertebrate eggs and weakly swimming polychaete sabellid embryos and larvae (at densities of 1.25-1.40 ind. L(-1)), while the second consisted of better-swimming copepods and polychaete spionid larvae (at densities of 0.70-1.65 ind. L(-1)). A canonical correlation analysis demonstrated that the former group occurred at sites with greater freshwater input, higher POC content and greater depth, whereas the latter group was significantly associated with sites subject to seawater and faster flows. We propose that a two-layered circulation process and tidally induced oscillations in water movements might account for the distributional differences between these two groups.

[Effects of NKG2D and its ligands RAE-1 and H60 on graft-versus-tumor response].

The study was purposed to explore the effects of NKG2D receptor and its ligands RAE-1 and H60 on graft-versus-tumor (GVT) response induced by MHC haploidentical bone marrow/spleen cell transplantation. Female (BALB/c x C57BL/6) F1 mice (CB6F1, H-2K(b/d)) inoculated with H22 cells to develop a solid tumor model were the recipients, and bone marrow mixed with spleen cells of the healthy male C57BL/6 (H-2K(b)) mice were the donor cells. GVT response was observed after transplantation that from donor cells T and NK cells were purged with anti-CD3 and anti-NK monoclonal antibody, and the NKG2D receptor was blocked with anti-NKG2D monoclonal antibody, the expression levels of RAE-1 and H60 mRNA in tumor tissue were measured by means of semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) at different time points after transplantation. The results showed that the GVT response of transplantation was reduced after in vitro depletion of T and NK cells or blocking NKG2D receptor in donor cells of the graft, the expression levels of RAE-1 and H60 mRNA in tumor tissue increased after transplantation of haploidential bone marrow mixed with spleen cells. It is concluded that NKG2D and its ligands RAE-1 and H60 may play important roles in GVT response.