Separation of the up-regulated genes under nitrogen starvation from Phaeodactylum tricornutum by suppression subtractive hybridization technology

Sixteen cDNA fragments of Phaeodactylum tricornutum were isolated and identified to be up-regulated under nitrogen starvation by suppression subtractive hybridization (SSH) technology in order to elucidate the molecular mechanism of the diatom nitrogen utilization. Seven of them have high similarity with the functional genes related to the utilization of nitrogen. Northern blotting analysis indicated that 5 genes, nitrate transporter gene (nrt), nitrite reductase gene (nir), ammonium transporter gene (amt), ATP-binding cassette transporter gene (abc), and purine permease gene (pup), were significantly up-regulated under nitrogen starvation

Studies on the utility of inorganic carbon in three strains of Microcystis aeruginosa

Frequent outbreaks of cvanobacterial blooms in eutrophic water-bodies throughout the whole country, in particular Microcystis, have been a great threat to water resources. Many researches have been carried out in the primary characteristics of Microcystis, among which, the studies on utility of inorganic carbon may help us further understand the effects of inorganic carbon to the formation of Microcystis bloom and possibly provide clues for the control of Microcystis blooms. In this paper, three strains of M. aeruginosa were studied on their responses of photosynthetic oxygen evolution to different extracellular concentration of dissolved inorganic carbon (DIC) under different photosynthetic conditions, respectively. When the temperature rose from 20 degrees C to 30 degrees C the photosynthetic oxygen evolution rate of M. aeruginosa increased. Their photosynthetic oxygen evolution rates were enhanced at high pH value, the maximum of which increased obviously from pH 7.0 to pH 9.0. While extracellular carbonic anhydrase inhibitor acetazolamide (AZ) showed little effect to the photosynthetic oxygen evolution of M. aeruginosa, intracellular and extracellular carbonic anhydrase inhibitor ethoxyzolamide (EZ) suppressed their photosynthetic oxygen evolution. Simulated with enzyme kinetic equation, their K-0.5(DIC) were, found to be less than 50,mu m, suggesting that M. aeruginosa has relatively high affinity for environmental dissolved inorganic carbon(DIC). The change of temperature had little effect on K-0.5 (DIC) of M. aeruginosa indicated that the ability of utilizing inorganic carbon of M. aeruginosa was not influenced by the temperature within certain range. With the rising of the medium pH, K-0.5 (DIC) of M. aeruginosa FACHB905 and M. aeruginosa PCC7806 increased while that of M. aeruginosa FACHB469 decreased. K-0.5 (DIC) of M. aeruginosa did not change when AZ or EZ was added to the medium. The responses of photosynthetic oxygen evolution of M. aeruginosa and Chlamydomonas reinhardtii under conditions of different pH value and addition of carbonic anhydrase inhibitors were also compared in this paper. The results showed that the photosynthetic oxygen evolution of C. reinhardtii decreased with the rising of pH value from 7.0 to 9.0 and was suppressed by both of AZ and EZ. K-0.5 (DIC) of C. reinhardtii also decreased with the rising of the medium pH and under the treatment of AZ or EZ

Construction of copper-induced gene expression platform in Synechocystis sp pcc6803

In Synechocystis sp. PCC6803, gene knock-out is the most straightforward and effective method to reveal the physiological function of a gene. Nevertheless, insertion mutants could not be generated for those genes essential to survival. In order V to elucidate the function of such genes in Synechocystis sp. PCC6803, a copper-induced gene expression platform was constructed using the promoter of petE (PpetE). PpetE from Synechocystis sp. PCC6803 and the beta-galactosidase gene (lacZ) from E. coli GM48 were cloned respectively by doing polymerase chain reaction (PCR), and the PpetE was positioned upstream of lacZ. The PpetE-lacZ construct was integrated into the genome of Synechocystis sp. PCC6803 via homologous recombinations. The expression of beta-galactosidase gene was found to be controllable by adjusting the concentration Of CU2+ in medium. In a range from 6 to 400nmol/L, Cu2+ induced the expression of beta-galactosidase in an S-shaped curve, but when the concentration of cu(2+) in medium was below 6nmol/L or above 400nmol/L, the activity of beta-galactosidase was either too low to be detected or too high to be regulated. This copper-induced gene expression platform can be used in the control of some indispensable genes in Synechocystis sp. PCC6803 : eel Is survived in the presence of Cu2+ so that the physiological effect of a gene Could be observed when Cu2+ is removed

Phylogenetic systematic inference in the Aspidogastrea (Platyhelminthes, Trematode) based on the 18s rRNA sequence

The subclass Aspidogastrea ( Platyhelminthes, Trematoda) is an archaic and minor group among parasitic platyhelminths, and comprises 4 families, of which the Aspidogastridae Poche 1 1907 is divided into three subfamilies, and other three families i.e. Stichocotylidae Faust & Tang, 1936, Rugogastridae Schell, 1973, and Multicalycidae Giboson & Chinabut, 1984 only contains a single genus each. However, there are still arguments on the phylogenetic relationships among these four families. In the present study, the 18S rRNA sequences of three aspidogastrid species, i.e. Aspidogaster coachicola, Aspidogaster ijimai and Multicalyx elegans were determined, and all published 18S rRNA gene data for aspidogastreans in the GenBank database were downloaded, in order to examine the phylogenetic relationships within the Aspidogastrea. According to the molecular data, nucleotide variations of 18S rRNA sequences across all eight species of aspidogastreans ranged from 1.1 % to 9.1 %, among 6 species of the Aspidogastridae from 1.1 % to 7.7 %, between Rugogaster hydrolagi of the Rugogastridae and six aspido-gastrid species from 8.2% to 9.1 %, whereas between Multicalyx elegans of the Multicalycidae and six aspidogastrid species only from 2.7% to 6.8%. Phylogenetic analyses of the 18S rRNA with the digenean species Paragonimus westermani as outgroup by the maximum parsimony (MP) and the maximum likelihood (ML) methods produced two identical topological trees. R. hydrolagi of the Rugogastridae locating at the base of phylogenetic trees, appears to be the sister group of all other aspidogastrean species, which form two main clades, the first comprising the Aspigogaster and the Lobatostoma of the Aspidogastrinae, and M. elegans, the second the Multicotyle of the Aspidogastrinae, and the Cotylaspis and the Cotylogaster of the Cotylaspidinae. Recognizing Multicalycidae, however, would make the Aspidogastidae paraphyletic. It suggested that the genus Multicalyx should revert to the family Aspidogastridae, and the Multicalycidae be invalid family name; furthermore, the adhesive disc, with marginal organ, consisting of alveoli, the adhesive disc, without marginal organ, consisting of well separated sucker, and of rugae, shoud be identified as the synapomorphy of the Aspidogastridae, the Stichocotylidae, and the Rugogastridae, respectively. In addition, both the Aspidogastrinae and the Cotylaspidinae were shown to be non-monophyletic, implying that the number of longitudinal rows of alveoli is the parallel evolution character, and being unrelevant to subfamilial relationships in the Aspidogastridae. Therefore, the subfamilial classification of the Aspidogastridae needs to be revised by examining more genera and species of aspidogastrids

Improvement of determination on TTC - Dehydrogenase activity in biofilms

The method of 3, 5, 5 - triphenyltetrazolium (TTC) determining biofilms activity was improved, and the problem that the standard curve of determination on TTC - dehydrogenase activity can't be made conveniently and stably was resolved. The factors which influence the determination were studied. The results showed that sodium sulfide as reducer, toluene as TF organic extractant, Tris - HCl as buffer solution, pH 8.6 and 38 degrees C were the best condition on the developed method, and the optimum reaction Lime to cultivate biofilms is 6 h

Establishment of cell model for the study of cytotoxicity induced by microcystin-LR

Microcystins are a group of closely related cyclic heptapeptides produced by a variety of common cyanobacteria. These toxins cause hepatocyte damage by inhibiting protein phosphastases I and 2A, resulting in hyperphosphorylation of a number of different proteins. Furthermore, high incidence of primary liver cancer in Qidong and Haimen in China has been associated with bloom contaminated drinking water. The mechanisms of MC-induced hepatotoxicity and tumor promotion activity have not been fully elucidated. In this study, Using 18 cell lines as materials, the cytotoxicity induced by different concentrations of microcystin-LR (20 and 50 mu g/mL) was studied. The morphological observation showed that five cell lines (PC-3, J82, 786-O, 5637 and VERO-E6) underwent obviously morphological changes after 30h treatment with microcystin-LR ( MCLR) with a dose-dependent manner. The cytoxicity of MCLR was determined by LDH leakage that showed a dose-dependent increase in five cell lines treated with MCLR, of which LDH leakage for 5637 and PC-3 were more serious under the same treatment. The SOD activity for five cell lines tended to increase in 20 mu g/mL MCLR treatment but sharply decrease in 50 mu g/mL MCLR treatment compared with the control cells; the GSH content decreased totally in different treatment. Based on the analysis of the sensitivity discrepancy for MCLR, 5637 cell lines was chosen for the establishment of a cell model for the study of cytotoxicity induced by microcystin-LR

Long-term changes of Copepoda community (1957-1996) in a subtropical Chinese lake stocked densely with planktivorous filter-feeding silver and bighead carp

In contrast to the relatively well documented impact of particulate-feeding fish on zooplankton communities, little attention has been devoted to the impact of filter-feeding fish. Filter-feeding silver and bighead carp are the most intensively cultured fish species in Asia and comprise much of the production of Chinese aquaculture. However, little information is known about the impact of either fish on the zooplankton community. Long-term changes in the Copepoda community (1957-1996) were studied at two sampling stations of a subtropical Chinese lake (Lake Donghu) dominated by silver and bighead carp. For both calanoids and cyclopoids, the littoral station (I) was much more resource profitable than the pelagic station (II). There has been a tremendous increase in the annual fish catch over the past 30 years due to the increased stocking with fingerlings of the two carp species. There was a notably higher fish density at Station I than at Station II. Cyclopoid abundance was notably higher at Station I than at Station II during the 1950s to the 1980s, while the reverse became true in the 1990s. This is probably because when fish abundance increased to an extremely high level, the impact of fish predation on the cyclopoids became more important than that of food resources at the littoral station. At both stations, cyclopoid abundance was relatively low in spite of the presence of abundant prey. Similarly, calanoid density did not differ significantly between the two stations in the 1950s and 1960s, but was significantly lower at Station I than at Station II during the 1980s and 1990s. Such changes are attributed to the gradient of fish predation between the stations and an increasing predation pressure by the fish. The increased fish predation also correlated with a shift in summer-dominant calanoids from larger species to smaller ones. In conclusion, the predaceous cyclopoids are affected by fish predation to a much lesser extent than the herbivorous calanoids, and therefore increased predation by filter-feeding fish results in a definite increase in the cyclopoid/calanoid ratio. Predation by filter-feeding fish has been a driving force in shaping the copepod community structure of Lake Donghu during the past decades

Ultrastructural examination on the tegument of procercoid of Bothriocephalus acheilognathi

The tegument of the procercoid of Bothriocephalus acheilognathi was studied by transmission electron microscopy (TEM) The tegument of the procercoid consists of an outer syncytial layer with underlaying perikarya. The outer portion of the tegument is composed of a dense layer of microtriches and some tumuli. The microtriches are longer and thicker than those on the adult worm, which are monomorphic and might be stripped off during their establishment in definite hosts and then re-occur on the tegument surface of adult worms. The tumuli are spaced on the anterior part of the procercoid, containing electron-dense inclusions. Three types of secretion processes are observed in the tegumental cytoplasm, i. e., apocrine, eccrine and microapocrine processes. The ducts of the penetration gland open at the hook region at the posterior end of the procercoid. Muscle bundles can be seen within the perinuclear region and just below the fibrous layer. The function of tumuli of procercoid also is discussed in this paper

Cloning and sequencing of the growth hormone gene of large yellow croaker and its phylogenetic significance

Using conserved primers and the PCR reaction, the growth hormone (GH) gene and the 3'-UTR of the large yellow croaker (Pseudosciaena crocea) were amplified and sequenced. The gene structure was analyzed and compared to the GH genes of 5 other percoid fish downloaded from Genbank. Also the GH gene of the large yellow croaker and the genes from 14 Percoidei and 2 Labroidei species were aligned using Clustal X. A matrix of 564 bp was used to construct the phylogenetic tree using maximum parsimony and neighbor-joining methods. Phylogenetic trees by the two methods are identical in most of the clades with high bootstrap support. The results are also identical to those from morphological data. In general, this analysis does not support the monophyly of the families Centropomidae and Carangidae. But our GH gene tree indicates that the representative species of the families Sparidae and Sciaenidae are a monophyletic group