Characterization of the dimer-monomer equilibrium of the papaya Copper/Zinc superoxide dismutase and its equilibrium shift by a single amino acid mutation.

The coding region of the copper/zinc superoxide dismutase (Cu/Zn SOD) cDNA from papaya fruit, Carica papaya L. cv. Tainong 2, was cloned into an expression vector, pET-20b(+). The Cu/Zn SOD was expressed in Escherichia coli and purified by His-tag technique. Two active forms of the enzyme (30% dimer and 70% monomer) in equilibrium were observed. The activity of the dimeric enzyme was higher than that of the monomeric form. The thermal inactivation rate constant K(d) values calculated for the dimer and monomer at 90 degrees C were -0.0203 and -0.0216 min(-1), and the half-lives for inactivation were 41.9 and 31.8 min, respectively. This indicated that the dimeric enzyme was more stable than its monomeric form. The dimerization of the enzyme was inhibited under acidic pH (below 3.0) or imidazole buffer (above 0.5 M), whereas it was not affected under alkaline pH (above 9.0). Both activity and forms of the enzyme were not affected by 1-4% SDS. Furthermore, the dimeric enzyme was much more resistant to proteolytic attack after 3 h of incubation at 37 degrees C with trypsin or chymotrypsin. In addition, mutation of the papaya Cu/Zn SOD at position 48 from Leu to Phe (L48F) affected the association of monomer, whereas a mutant with Lys substitution (L48K) at the same position tended to dissociate into monomeric form.     

Molecular characterization and pathogenicity of Francisella noatunensis subsp. orientalis isolated from cultured tilapia (Oreochromis sp.) in Taiwan

Francisella noatunensis subsp. orientalis is a causative agent of systemic granulomatous disease in tilapia. The present study was designed to understand the genetic and phenotypic diversities among Taiwanese Fno isolates obtained from tilapia (n = 17) and green Texas cichlid (Herichthys cyanoguttatus) (n = 1). The enzymatic profiles of the isolates were studied using the API ZYM system. Phylogenetic tree analysis of the 16S rRNA and housekeeping gene and pulsed‐field gel electrophoresis (PFGE) were carried out to determine the genotypic characters of all isolates. The phylogenetic tree showed similarity of 99%–100% nucleotide sequences of 16S rRNA and housekeeping genes compared to the Fno references genes from GenBank database. Comparatively, the results revealed an identical profile of enzymatic and PFGE pattern which was distincted from that of F. philomiragia. To understand the pathogenicity, the isolates were intraperitoneal injected to tilapia the gross lesions were observed concomitant with natural outbreak. Median lethal dose upon Nile tilapia and red tilapia were 9.06 × 10³ CFU/fish and 2.08 × 10² CFU/fish, respectively. Thus, our data provide understanding the epidemiology of Taiwanese Fno isolates, and help in development of future control and prevention.     

Conversion of Squid Pen to Homogentisic Acid via Paenibacillus sp. TKU036 and the Antioxidant and Anti-Inflammatory Activities of Homogentisic Acid

The culture supernatant of Paenibacillus sp. TKU036, a bacterium isolated from Taiwanese soils, showed high antioxidant activity (85%) when cultured in a squid pen powder (SPP)-containing medium at 37 °C for three days. Homogentisic acid (2,5-dihydroxyphenylacetic acid, HGA) was isolated and found to be the major antioxidant in the culture supernatant of the SPP-containing medium fermented by Paenibacillus sp. TKU036. Tryptophan was also present in the culture supernatant. The results of high-performance liquid chromatography (HPLC) fingerprinting showed that HGA and tryptophan were produced via fermentation but did not pre-exist in the unfermented SPP-containing medium. Neither HGA nor tryptophan was found in the culture supernatants obtained from the fermentation of nutrient broth or other chitinous material, i.e., medium containing shrimp head powder, by Paenibacillus sp. TKU036. The production of HGA via microorganisms has rarely been reported. In this study, we found that squid pen was a potential carbon and nitrogen source for Paenibacillus sp. Tryptophan (105 mg/L) and HGA (60 mg/L) were recovered from the culture supernatant. The isolated HGA was found to have higher antioxidant activity (IC₅₀ = 6.9 μg/mL) than α-tocopherol (IC₅₀ = 17.6 μg/mL). The anti-inflammatory activity of the isolated HGA (IC₅₀ = 10.14 μg/mL) was lower than that of quercetin (IC₅₀ = 1.14 μg/mL). As a result, squid pen, a fishery processing byproduct, is a valuable material for the production of tryptophan and the antioxidant and anti-inflammatory HGA via microbial conversion.     

气候变化对沧州金丝小枣产量的影响及对策研究

根据沧州气候变化和金丝小枣产量的资料,研究气候变化对金丝小枣产量的影响及对策.结果表明:近5 a与前10 a相比,由于气候变化导致的熟前增长期日照时数的变化,夏季降水量的变化,成熟收获期日照时数和平均气温的变化,成熟收获期降水量的变化对金丝小枣的产量都有明显的影响.可以通过建设烘干房,加强针对性的气象灾害预警服务等措施来减轻灾情.     

拟南芥AAP1基因的克隆及植物表达载体的构建

拟南芥氨基酸透性酶1(AAP1,也叫NAT1)是植物中第一个被分离的氨基酸转运蛋白,在拟南芥主根、侧根、根毛及根表皮细胞中均有增加氨基酸含量的作用。本研究利用RT-PCR的方法,从拟南芥中克隆了该基因,测序结果与GenBank(NM-104616.4)中已发表的拟南芥AAP1(AtAAP1)基因的同源性高达99.93%;并将AtAAP1基因与pCAMBIA3300构建p3300-AAP1植物表达载体,为过表达AtAAP1基因,提高作物氨基酸含量,从而改善作物氮素利用效率提供参考。     

河北献县表层土壤全氟空间变异性特征分析

为了对河北献县土壤改良及对地氟病的防治提供指导性建议,采用地理信息系统与地统计相结合的方法对研究区表层土壤全氟的空间变异特征进行了分析。结果表明:献县表层土壤全氟经对数转换后符合指数模型,全氟具有很强的空间相关性,说明其有明显的可迁性特点,受水文地质、地形等自然结构性因素影响较大而受人为因素影响较小;用Kriging内插法对未测区域全氟进行最优估计,并形成插值图,可更直观的反映出研究区内表层土壤全氟的空间变异特征。从整体上看献县表层土壤全氟含量呈现东南西三部含量高而北部偏低的分布特征,其分布特征受河流走向影响较大且远离河床处氟含量呈渐增趋势。     

灰葡萄孢诱变菌株毒素的除草活性研究

 对灰葡萄孢BC4菌株进行紫外线诱变得到了15个诱变菌株, 经测定筛选出BC4-1、BC4-2和BC4-15等3个诱变菌株中以BC4-1菌株效果最好。试验发现，用于毒素产生的PD培养基的pH 值对产毒能力影响很大，以pH 4.0最优。用三氯甲烷、石油醚、乙酸乙酯萃取培养滤液制备BC-粗毒素，生物测定结果表明，以乙酸乙酯萃取所得粗毒素对杂草种子萌发及生长抑制作用最强。通过柱层析法和HPLC法分离和纯化除草活性组分,得到1个在271 nm有最大UV吸收的化合物,该组分在100 mg·L-1浓度下对马唐的生长具有强烈的抑制作用，在50 mg·L-1浓度下可完全抑制马唐和反枝苋种子的萌发。     

青龙湾沙区土壤养分状况分析

为了研究不同植被类型对沙区土壤的改良效果,调查沙区土壤的养分状况,笔者对青龙湾沙区不同植被类型的土壤有机质、有效氮、速效钾、有效磷等指标进行分析。结果表明,青龙湾沙区土壤pH值范围为7.40~7.72,土壤呈中性略偏微碱性;土壤有机质、有效氮、有效磷及速效钾含量偏低。有机质含量对于土壤其他营养元素的含量和有效性均具有比较大的影响。不同植被类型对沙区土壤的改良具有一定的差异,除农田外,果园、毛白杨刺槐混交林的改良效果较好,小叶杨林改良效果较差。总体来说,经过生态林改良后的土壤养分状态得到明显改善。