基于动力学模型的法夫酵母发酵生产虾青素的补料策略优化

对法夫酵母的不同补料发酵方式进行了研究.基于底物抑制模型,提出了一种优化的两阶段补料策略,用于法夫酵母产虾青素的高密度发酵.在发酵的延迟期和对数生长期早期,糖浓度控制在25 g/L左右,在此条件下,生物量可以达到最大,且时间缩短.在对数生长期后期及稳定期,糖浓度控制在5 g/L,虾青素的合成时间可以有效延长.与传统的补料方式相比,采用此补料策略取得了较好的发酵效果.发酵终点细胞干重达到23.8g/L,虾青素产量达到29.05 mg/L,分别比分批发酵提高了52.8%和109%.     

金黄色葡萄球菌基因表达的DNA扣除法

[目的]金黄色葡萄球菌作为一种分布广泛的致病微生物和研究革兰氏阳性菌遗传背景的模式菌株,利用real-time RT PCR对相关毒素及调控基因进行表达定量分析,在生物、医学、食品检测等领域具有较大研究价值.[方法]对制备好的反转录(RT,含有cDNA和DNA)和非反转录(RTˉ,仅含DNA)样品进行Real-time PCR检测,根据经典(1 E)ˉ△△Ct相对定量算法并结合PCR效率公式建立一种基因表达相对定量分析的DNA扣除法,将得到的Ct值转换为各样品含量,从RT样品中扣除RTˉ样品的量,无需DNaseⅠ酶解处理就可以去除DNA的影响,RTˉ样品的检测结果还可同时作为稳定的DNA内参.[结果]采用以上方法分析金黄色葡萄球菌肠毒素A基因(sea)、16S rRNA和RNA Ⅲ的表达情况,在含有葡萄糖的NB培养基中sea的相对转录水平随着葡萄糖浓度的增大而升高,RNAⅢ的相对转录水平随葡萄糖浓度的变化而产生小幅度的波动,16S rRNA在菌体生长初期时的表达量较为稳定;与绝对定量法比较,结果差异较小(均小于15%),且差异不显著(p＞0.05).[结论]这种基于DNA扣除法的Real-time RT PCR相对定量方法可以有效的对金黄色葡萄球菌的基因表达进行分析.     

Allelopathic effects of Ulva lactuca on selected species of harmful bloom-forming microalgae in laboratory cultures

Allelopathic effects of the green macroalgae Ulva lactuca on the growth of three species of red tide microalgae, Heterosigma akashiwo, Alexandrium tamarense, and Skeletonema costatum were tested in laboratory co-cultures precluding the nutrient and light limitation and the effect of high pH. The growth of all three species of microalgae was significantly (p < 0.01) inhibited by fresh U. lactuca. In nutrient replete semicontinuous co-cultures with U. lactuca, H. akashiwo was completely dead in 12 days, and the growth of A. tamarense and S. costatum was reduced by 48 and 46%, respectively by U. lactuca within 12 days. The U. lactuca culture filtrate exhibited a significant (p < 0.05) inhibitory effect on the microalgae in the first 1 or 2 days, but growth resumed in the following days, and S. costatum growth was slightly (p > 0.05) promoted from day 3. The results suggested that the allelopathic compounds are quickly degradable and a long-term inhibition might need the continuous addition of compounds originated from macroalgae. Dried U. lactuca also exhibited inhibitory effects on the microalgae, and the normalized mean growth rates of microalgae decreased with the biomass of dried U. lactuca. The dependent relationships were y = −2.1208x² + 1.0159x + 0.9752 for H. akashiwo, y = 0.7133x² − 3.5813x + 1.1665 for A. tamarense, and y = −0.2114x² − 1.063x + 1.0873 for S. costatum, respectively. The potential feasibility of utilization of dried U. lactuca against red tide microalgae was 2.0 g dry wt L⁻¹. The present study shows that U. lactuca exhibits negative allelopathic effects on harmful bloom-forming microalgae.     

Mutation mechanism of chlorophyll-less barley mutant <Emphasis Type="Italic">NYB</Emphasis>

NYB is chlorophyll-less barley mutant, which is controlled by a recessive nuclear gene. The mutation mechanism is revealed. The activities of enzymes transforming 5-aminolevulinic acid into protochlorophyllide were the same in both NYB and the wild type (WT), but the activity of the protochlorophyllide oxidoreductase (POR) in WT was much higher than that of NYB. Most of the photosystem 2 apoproteins were present in both WT and NYB, suggesting that the capability of protein synthesis was probably fully preserved in the mutant. Thus chlorophyll (Chl) biosynthesis in NYB was hampered at conversion form protochlorophyllide (Pchlide) into chlorophyllide. The open reading frame of porB gene in NYB was inserted with a 95 bp fragment, which included a stop codon. The NYB mutant is a very useful material for studies of Chl biosynthesis, chloroplast signalling, and structure of light-harvesting POR-Pchlide complex (LHPP).     

Candida dajiaensis sp. nov., Candida yuanshanicus sp. nov., Candida jianshihensis sp. nov., and Candida sanyiensis sp. nov., four anamorphic, ascomycetous yeast species isolated from soil in Taiwan

Nine anamorphic, ascomycetous yeast strains belonging to the Pichia anomala clade were recovered from forest soil in 2006 in Taiwan. The nine yeast strains represent four novel yeast species based on the sequences of their D1/D2 domain of the large subunit (LSU) rRNA gene and their physiological characteristics. The scientific names of Candida dajiaensis sp. nov., Candida yuanshanicus sp. nov., Candida jianshihensis sp. nov., and Candida sanyiensis sp. nov. are proposed for these novel yeast species. The type strains are C. dajiaensis SM11S03(T) (=CBS 10590(T)=BCRC 23099(T)), C. yuanshanicus SY3S02(T) (=CBS 10589(T)=BCRC 23100(T)), C. jianshihensis SM8S04(T) (=CBS 10591(T)=BCRC 23096(T)), and C. sanyiensis SA1S06(T) (=CBS 10592(T)=BCRC 23094(T)). Sequence analysis of the D1/D2 of the LSU rRNA gene revealed that the three species, C. dajiaensis, C. yuanshanicus and Pichia onychis, shared a separate branch in the phylogenetic tree, C. jianshihensis is phylogenetically related to Candida ulmi and Pichia alni, and the phylogenetically closest relative of C. sanyiensis is Pichia populi.     

Creation and analysis of a novel chimeric promoter for the complete containment of pollen- and seed-mediated gene flow

Effective containment of gene flow in transgenic plants requires a promoter that is highly specific for male and female gametes or tissues. Here, we report the creation of a novel pollen-, stigma- and carpel-specific (PSC) promoter through the fusion of the pollen-specific LAT52 and carpel-specific AGL5 enhancers to a stigma-specific SLG promoter. Gene expression analysis showed that fusion of the LAT52 enhancer to the SLG promoter enables the latter to gain pollen-specific activity while the acquirement of carpel-specific activity requires the correct orientation of the inserted AGL5 enhancer in the PSC promoter, and only a forward- but not a reverse-oriented one is functional. The resulting fPSC promoter, when fused to DT-A, generated at least three aberrant gynoecium phenotypes. Type I plants exhibited shortened stigmatic tissues, resembling plants containing the DT-A gene controlled by the SLG promoter. However, type II and III plants displayed partial or complete ablation of gynoecia, and were unable to support the reproductive process. Type II and III plants also produced severely perturbed anthers and pollen in comparison to type I or SLG::DT-A plants, and transgenic pollen grains were unable, when out-crossed with control plants, to pass the transgene to the next generation in all plants examined, indicating that they are selectively eliminated. This tissue-specific ablation or perturbation is highly specific, and does not compromise vegetative growth. Evidently, the fPSC promoter faithfully acquires tissue specificity from the incorporated enhancers and promoter, and should have a practical application for transgene containment in non-fruit and -grain producing plant crops.     

Microbial subversion of heparan sulfate proteoglycans

The interactions between the host and microbial pathogen largely dictate the onset, progression, and outcome of infectious diseases. Pathogens subvert host components to promote their pathogenesis and, among these, cell surface heparan sulfate proteoglycans are exploited by many pathogens for their initial attachment and subsequent cellular entry. The ability to interact with heparan sulfate proteoglycans is widespread among viruses, bacteria, and parasites. Certain pathogens also use heparan sulfate proteoglycans to evade host defense mechanisms. These findings suggest that heparan sulfate proteoglycans are critical in microbial pathogenesis, and that heparan sulfate proteoglycan-pathogen interactions are potential targets for novel prophylactic and therapeutic approaches.     

Estimation of genetic parameters for disease‐resistance traits in Cynoglossus semilaevis (Günther, 1873)

The objective of this study was to estimate genetic parameters for three traits based on 28 Cynoglossus semilaevis families approximately 6 months of age (at least 5 cm total length), including trait_1 (survival of 26 families, 3434 individuals in total subjected to challenge tests with Edwardsiella tarda), trait_2 (survival of 20 families, 2016 individuals in total subjected to challenge tests with Vibrio anguillarum) and trait_3 (survival of 27 families, 9340 individuals tagged at circa 180 days of age and reared in indoor ponds for circa another 5 months). The result showed that there were large differences in the survival of the families after challenge (11.11–65.31% for E. tarda and 9.18–70.54% for V. anguillarum). Additionally, the survival of families reared in indoor ponds was also different, varying from 21.00% to 73.67%. Heritabilities of the three traits varied from 0.14 to 0.26, as estimated by the linear model (LM) and the threshold model (TM). The trait_1 heritabilities (0.26 and 0.19 estimated by LM and TM) were higher than those of the others (0.20 and 0.23 estimated by LM, 0.14 and 0.19 estimated by TM). The estimates of heritabilities using LM were consistently higher than those of TM in this study. There were significant medium genetic correlations of 0.44 and 0.42 between trait_1 and trait_2 obtained from LM and TM (P < 0.05). However, very low and non‐significant genetic correlations of trait_1 and trait_3 (?0.10 for LM, ?0.05 for TM), as well as those of trait_2 and trait_3 (0.05 for LM, 0.04 for TM) were obtained. Therefore, indirect selection for trait_1 and trait_2 was effective, but almost ineffectual for trait_1 and trait_3 as well as trait_2 and trait_3. Otherwise, there was no significant difference in the predictive abilities of LM and TM. Two families resistant to both Edwardsiella tarda and Vibrio anguillarum were selected plus one family resistant to both Vibrio anguillarum and naturally infected by unknown pathogens through family selection. As there was very low and non‐significant genetic correlation of trait_3 and trait_1 as well as trait_2, superior strains are anticipated with the ability to resist two or more kinds of diseases, through the crossing of families selected for the three traits described above. The results support the hypothesis that genetic variation exists for disease survival, which could be used to design a breeding program for selecting strains of Cynoglossus semilaevis with high disease resistance.     

非洲紫罗兰叶片脱分化过程中核酸蛋白质和滨粉含量动态的研究

本文测定了非洲紫罗兰（Ｓａｉｎｔｐａｕｌｔａｉｏｎａｎｔｈａ）叶片脱分化过程中核酸、蛋白质和波粉的含量。结果表明：发生脱分化的叶片中的蛋白质和淀粉含量均低于对照,而ＲＮＡ含量则高于对照,ＤＮＡ含量无明显差异。叶片培养的第一天内,发生脱分化的叶片中的蛋白质含量明显下降,对照中的蛋白质含量上升。脱分化过程中,淀粉含量有一个上升、下降、再上升的变化过程,对照中淀粉含量一直上升。     

脐血浆治疗大鼠实验性肝衰竭及其机制的研究

本文采用脐血浆治疗实验性肝衰竭大鼠模型,并与成人血浆的疗效进行了比较。结果表明,脐血浆降低大鼠死亡率、血谷丙转氨酶水平,总胆红素浓度及使甲胎蛋白水平升高均明显高于成人血浆的作用（Ｐ＜０．０５）．肝脏病理组织学也显示脐血浆具有减轻病理损害和较快修复坏死组织的作用。提示脐血浆中含有促进肝细胞再生的因子,具有显著提高实验性大鼠肝衰竭的存活率。