一株虾池来源的螺旋拟柱孢藻藻株的分离鉴定及重金属离子Cu~(2+)、Cd~(2+)和Pb~(2+)对其生长的影响

【目的】探讨凡纳滨对虾养殖水体中入侵蓝藻拟柱孢藻的生长生理特性。【方法】从汕头澄海人工对虾养殖池分离纯化藻株,通过形态及其16SrRNA基因鉴定,之后在CT与BG11两种蓝藻通用培养基的基础上优化最佳培养条件,最后分析了不同浓度的3种重金属离子即Cu~(2+)(0–0.8 mg/L)、Cd~(2+)(0–4 mg/L)和Pb~(2+)(0–80 mg/L)对藻株生长的影响。【结果】澄海虾池来源的分离纯化藻株形态呈卷曲螺旋型,16S rRNA基因序列与多株其他来源的拟柱孢藻相似度均达98%以上。实验室培养,藻株最佳生长状态的培养条件是在BG11培养基的基础上调整氮浓度及氮磷比分别为N 62 mg/L,N︰P=9︰1,在此条件下,藻丝生物量可达(0.632±0.170)×107/L,藻丝比平均生长速率最高为(0.063±0.001)/d。本分离藻株活体对重金属Cu~(2+)、Cd~(2+)和Pb~(2+)具有一定的耐受性,其耐受浓度范围分别为0–0.2、0–0.5和1–40 mg/L,其中,Cu~(2+)和Cd~(2+)对藻的生长具有抑制作用,而且此抑制作用随着金属离子剂量的增加及作用时间的延长更加显著,Cu~(2+)和Cd~(2+)对藻体的半数抑制浓度(96 h EC50)分别为0.125和0.551 mg/L;而浓度范围为0–80 mg/L的Pb~(2+)对藻体的生长则表现为低剂量(≤40 mg/L)呈促进,高剂量(≥80 mg/L)则抑制。【结论】从凡纳滨对虾养殖池中分离鉴定出一株形态呈螺旋型的拟柱孢藻,命名为螺旋拟柱孢藻(Cylindrospermopsis raciborskii helix),本藻株活体能够在一定浓度的Cu~(2+)、Cd~(2+)和Pb~(2+)中生长,为螺旋拟柱孢藻活藻生物吸附重金属离子而改善虾池水体环境提供了可能性。     

Constitutively solvent-tolerant Pseudomonas taiwanensis VLB120∆ C∆ ttgV supports particularly high-styrene epoxidation activities when grown under glucose excess conditions

Solvent-tolerant bacteria represent an interesting option to deal with the substrate and product toxicity in bioprocesses. Recently, constitutive solvent tolerance was achieved for Pseudomonas taiwanensis VLB120 via knockout of the regulator TtgV, making tedious adaptation unnecessary. Remarkably, ttgV knockout increased styrene epoxidation activities of P. taiwanensis VLB120Δ C. With the aim to characterize and exploit the biocatalytic potential of P. taiwanensis VLB120Δ C and VLB120Δ CΔ ttgV, we investigated and correlated growth physiology, native styrene monooxygenase (StyAB) gene expression, whole-cell bioconversion kinetics, and epoxidation performance. Substrate inhibition kinetics was identified but was attenuated in two-liquid phase bioreactor setups. StyA fusion to the enhanced green fluorescent protein enabled precise enzyme level monitoring without affecting epoxidation activity. Glucose limitation compromised styAB expression and specific activities (30–40 U/g _CDW for both strains), whereas unlimited batch cultivation enabled specific activities up to 180 U/g _CDW for VLB120Δ CΔ ttgV strains, which is unrivaled for bioreactor-based whole-cell oxygenase biocatalysis. These extraordinarily high specific activities of constitutively solvent-tolerant P. taiwanensis VLB120∆ C∆ ttgV could be attributed to its high metabolic capacity, which also enabled high expression levels. This, together with the high product yields on glucose and biomass obtained qualifies the VLB120∆ ttgV strain as a highly attractive tool for the development of ecoefficient oxyfunctionalization processes and redox biocatalysis in general.     

混合喂养法建立成年营养性肥胖大鼠模型

目的:尝试用混合喂养法建立一种与临床相仿的成年营养性肥胖大鼠模型。方法:55只8周龄SD大鼠随机分为对照组10只(普通饲料喂养)和实验组45只(混合喂养),喂养2周后实验组剔除肥胖抵抗大鼠。每周记录大鼠体重,喂养9周后观察两组大鼠体重、体长、Lee's指数、空腹血糖(FBG)、血脂、葡萄糖耐量水平和肝脏组织病理改变。结果:喂养第9周末,实验组大鼠和对照组大鼠体重分别为(645.6±34.8)g和(483.3±31.5)g,Lee's指数分别为(326.3±24.2)和(302.7±19.8),组间比较有显著差异(P0.05)。实验组血清甘油三酯(TG)、总胆固醇(TC)及低密度脂蛋白胆固醇(LDL-C)、FPG、糖负荷后30、60、120分钟血糖均明显高于对照组,差异有统计学意义。HE染色病理结果显示实验组大鼠肝脏均出现脂肪样变,而对照组未见明显变性。结论:本研究所应用的混合喂养法可以稳定成功地建立伴有葡萄糖耐量减低和高脂血症的成年营养性肥胖大鼠模型。     

Oxygen supply limits the heat tolerance of lizard embryos

The mechanisms that set the thermal limits to life remain uncertain. Classically, researchers thought that heating kills by disrupting the structures of proteins or membranes, but an alternative hypothesis focuses on the demand for oxygen relative to its supply. We evaluated this alternative hypothesis by comparing the lethal temperature for lizard embryos developing at oxygen concentrations of 10–30%. Embryos exposed to normoxia and hyperoxia survived to higher temperatures than those exposed to hypoxia, suggesting that oxygen limitation sets the thermal maximum. As all animals pass through an embryonic stage where respiratory and cardiovascular systems must develop, oxygen limitation may limit the thermal niches of terrestrial animals as well as aquatic ones.     

Mapping the genome of Miscanthus sinensis for QTL associated with biomass productivity

In light of rising energy costs, lignocellulosic ethanol has been identified as a renewable alternative to petroleum-based transportation fuels. In an attempt to reach government mandated ethanol production levels, potential plant biofeedstock candidates have been investigated, and cold-tolerant, perennial accessions within the C₄ grass genus Miscanthus have been identified as leading contenders in the Midwestern US. To facilitate the development of improved cultivars through marker-assisted breeding, a quantitative trait locus (QTL) study was conducted on a full-sib, F₁ mapping population segregating for flowering time, height, leaf width, and yield using a genetic map consisting of 846 segregating SNP and SSR markers. This was a 3 year study investigating the genetic architecture underlying traits important to biomass production in a population of 221 progeny from a cross between M. sinensis ‘Grosse Fountaine’ and M. sinensis ‘Undine’ established in the spring of 2010; 72 QTLs with LOD scores above the genome-wide, permuted threshold equivalent to a P-value of 0.05 were identified across 13 traits. Of the 36 QTLs identified in 2011, 22 were detected again the following year. Both the use of spring emergence and vigor rating as a covariate to account for variation related to differences in establishment increased the power to detect QTLs in the 2 year establishment period. Finally, a dry period in the middle of the 2012 growing season suggested that yield declines were due to a decrease in tiller diameter.     

Bad guys turned nice? A critical assessment of Wolbachia mutualisms in arthropod hosts

Wolbachia are the most abundant bacterial endosymbionts among arthropods. Although maternally inherited, they do not conform to the widespread view that vertical transmission inevitably selects for beneficial symbionts. Instead, Wolbachia are notorious for their reproductive parasitism which, although lowering host fitness, ensures their spread. However, even for reproductive parasites it can pay to enhance host fitness. Indeed, there is a recent upsurge of reports on Wolbachia‐associated fitness benefits. Therefore, the question arises how such instances of mutualism are related to the phenotypes of reproductive parasitism. Here, we review the evidence of Wolbachia mutualisms in arthropods, including both facultative and obligate relationships, and critically assess their biological relevance. Although many studies report anti‐pathogenic effects of Wolbachia, few actually prove these effects to be relevant to field conditions. We further show that Wolbachia frequently have beneficial and detrimental effects at the same time, and that reproductive manipulations and obligate mutualisms may share common mechanisms. These findings undermine the idea of a clear‐cut distinction between Wolbachia mutualism and parasitism. In general, both facultative and obligate mutualisms can have a strong, and sometimes unforeseen, impact on the ecology and evolution of Wolbachia and their arthropod hosts. Acknowledging this mutualistic potential might be the key to a better understanding of some unresolved issues in the study of Wolbachia–host interactions.     

Potential of Mauritius Hemp (Furcraea gigantea Vent.) for the Remediation of Chromium Contaminated Soils

The present study was conducted to evaluate the ability of a high biomass producing, drought tolerant succulent plant Mauritius hemp (Furcraea gigantea Vent.) for its tolerance to different levels of Cr (0, 25, 50, 100 and 200 mg Cr kg soil^?1) and its potential for phytoremediation purposes. Based on the data on inhibition of the growth of plants with Cr, tolerance index and grade of growth inhibition, it was observed that the plant could tolerate up to 50 mg Cr kg ^?1 soil. Absorption of Cr from soil to plant and its translocation into plant tissues were discussed in terms of bio concentration factor (BCF), transfer factor (TF), and translocation efficiency (TE%). Cr was mainly accumulated in the roots and exclusion of Cr was found to be the principal physiological tolerance mechanism followed by a marked increase in proline, ascorbic acid, total free amino acids in the leaf tissue and malic acid in the rhizosphere samples to counter Cr stress. Based on the tissue concentration of Cr (< 300 μg g^?1 in the leaves and TF<1), it was concluded that, Furcraea gigantea could not be considered a hyperaccumulator and therefore unsuitable for phytoextraction of Cr. Nevertheless, Furcraea gigantea could be a suitable candidate for phytostablization of Cr contaminated soils.