微藻去除重金属镉的抗性机理研究进展

与水体中重金属去除的传统方法相比,生物吸附法是一种更具经济效益和环境效益的技术。微藻由于自身的廉价性和高吸附性已成为高效生物吸附剂的材料来源。要评价微藻在镉(Cd)去除方面的应用潜力,解析微藻抗重金属的机理是必要条件。因此,本文从抗Cd微藻种类,Cd对微藻光合作用、生长及结构的影响,胞外吸附的机理,胞内积累的机理,以及基因调控水平,阐述了目前微藻抗Cd的研究进展,以期为后续的研究提供理论帮助。     

热带地区不同水稻品种对土壤镉胁迫的生理生化响应

以热带地区主栽品种博优225和矮糯为材料,采用盆栽试验研究了不同水稻品种对土壤外源重金属Cd胁迫的耐性机理。结果表明:在各浓度镉胁迫下,2个品种水稻都是根累积的镉含量要高于茎叶和稻壳、糙米,即根>茎叶>稻壳>糙米;随着镉胁迫浓度的增加,细胞膜受损的伤害程度越大,矮糯质膜透性略高于博优225;随着Cd浓度的升高,水稻叶片丙二醛(MDA)、脯氨酸含量逐渐增加,且博优225的增加幅度明显大于矮糯,超氧化物歧化酶(SOD)和过氧化物酶(POD)活性均呈上升趋势,且博优225明显高于矮糯;过氧化氢酶(CAT)活性呈下降趋势;表明同样条件下博优225受Cd毒害更严重。     

不同品种万寿菊对镉胁迫的生长和生理响应

以6个万寿菊品种为研究对象,研究了不同浓度的重金属镉（Cd）胁迫（0、200、400、600 mg/L）对万寿菊基径、株高以及百叶重、茎叶重和单花质量等生长指标及其质膜透性（丙二醛、相对电导率）、保护酶活性（SOD、POD、CAT、APX）以及光合特性(叶绿素含量、净光合速率、气孔导度、蒸腾速率、水分利用效率)等生理指标的影响。结果显示:(1)低于400 mg/L的Cd胁迫对6个万寿菊品种的基径、株高无明显影响,而百叶重、茎叶重和单花质量却随着Cd浓度的增加显著降低,尤其是‘大英雄’和‘迪阿哥’2个品种表现的抗性较差。(2)随着Cd胁迫浓度的增加,各品种丙二醛（MDA）含量和相对电导率（REC）显著增加,而其保护酶活性不同程度降低。(3)Cd胁迫降低了万寿菊的叶绿素Chl a+b含量和Chl a/b,且抗性差的品种降低的幅度更大;叶片净光合速率（Pⁿ）明显降低,但蒸腾速率(T^r)和气孔导度(G^s)相对降幅较小,对水分利用效率（WUE）影响较小。研究表明,不同品种万寿菊对Cd毒害响应存在明显的差异,且Cd胁迫下生理响应的差异是品种间耐性差异的重要原因之一;抗性差的品种在高浓度Cd胁迫下,光合作用能力降低,抗氧化系统酶的活性受到显著抑制,膜质过氧化加剧,且品种‘珍妮’和‘金门’的抗性强于其他品种,可选择作为Cd污染区栽植植物。     

辣椒对镉胁迫的生理响应

以福湘5号、兴蔬215和川腾1号这3个辣椒品种为材料,用含有0mg/L、100mg/L、200mg/L、300mg/L重金属镉的1/2霍格兰培养液对具10片真叶的辣椒苗进行处理,7d后测定各项生理指标。结果表明,镉对辣椒的生长有很强的毒害作用,随着镉胁迫浓度的升高,3个辣椒品种的生物量、叶片叶绿素含量、电导率、丙二醛含量和活性氧清除系统酶活性都受到了不同程度的影响。在镉胁迫下,辣椒植株的株高、根长、鲜重受到明显抑制,根系发育畸形,叶片黄化。镉胁迫的毒害作用在3个辣椒品种间有差异。其中川腾1号耐镉胁迫能力较强,福湘5号次之,兴蔬215最差。     

珙桐幼苗生理生化指标对重金属铅、镉胁迫的响应

铅和镉在土壤中表现出很强的毒性,严重危害植物的生长发育.该研究着眼于中国特有濒危珍稀植物珙桐,探究盆栽实验条件下其抗氧化酶活性、丙二醛(MDA)以及游离脯氨酸、可溶性蛋白对不同浓度重金属铅、镉胁迫的响应规律.结果表明:(1)不同浓度铅处理下,珙桐幼苗MDA浓度均显著高于对照组,而镉胁迫条件下除10 mg·kg-1浓度外...     

产油微藻筛选和鉴定及其产油性能的研究

为了筛选具有产油能力的微藻,从自然界水体中分离出14株微藻,根据形态特点对它们进行了初步鉴定。对其中12株微藻在自养和异养条件下的生长特性和产油性能进行了比较。通过微藻的生长曲线,生物量和油脂含量等指标,从中筛选出高产藻株并对该藻株进行了分子生物学鉴定。结果表明:藻株Y06在12种微藻中的油脂产量和产率最高,经18S rDNA鉴定确定为栅藻(Scenedesmus abundans)。藻株Y06在自养条件下的油脂产率为9.40 mg/(L.d),在异养条件下的油脂产率为201.29 mg/(L.d)。     

富油能源微藻的筛选及产油性能评价

为了筛选具有产油潜力的能源微藻,以实验室保藏的20株淡水和海洋微藻(绿藻门18株,真眼点藻纲1株,硅藻纲1株)为研究对象,利用光径为3 cm柱状光生物反应器通气分批培养,通过测定微藻培养物的生物量和总脂含量等指标,从中筛选生长速度快、生物量和总脂含量高的微藻。结果表明:20株微藻的生物量和总脂含量分别在1.81~7.88g/L和16.0%~55.9% dw(% Dry weight)之间,筛选得到具有产油潜力的微藻9株,分别是栅藻(Scenedesmus sp.)(6.34g/L,55.9% dw)、麻织绿球藻(Chlorococcum tatrense)(5.93g/L,46.9% dw)、眼点拟微绿球藻(Nannochloropsis oculata)(7.88g/L,35.0% dw)、油面绿球藻(Chlorococcum oleofaciens)(5.58g/L,45.9% dw)、多形拟绿球藻(Pseudochlorococcum polymorphum)(6.10g/L,40.0% dw)、八月衣藻(Chlamydomonas augustae)(5.78g/L,40.5% dw)、椭圆小球藻(Chlorella ellipsoidea)(5.56g/L,40.7%dw)、椭圆绿球藻(Chlorococcum ellipsoideum)(5.41g/L,38.0% dw)、雪绿球藻(Chlorococcum nivale)(5.55g/L,36.3% dw),其中最具产业化潜力的微藻为栅藻(Scenedesmus sp.),其总脂收获量和单位体积总脂产率分别为3.5 g/L和218.7mg/L·d。     

产油微藻的分离、筛选及自养培养氮源、碳源的优化

从云南滇池的水样中分离筛选得到一株自养产油小球藻(Chlorella vulgaris,C.vulgaris),其油脂产率可达28.6mg/(L·d),进一步考察了不同氮源、氮源浓度和添加无机碳源对其自养生长和油脂积累的影响。结果表明,硝酸钠为优化氮源,氮元素的优化浓度为123mg/L,油脂含量随氮元素浓度升高而降低;添加NaHCO3显著提高了C.vulgaris生物量产率和油脂产率,其优化浓度为800mg/L。在氮源和碳源的优化浓度下,C.vulgaris的最大生物量产率和油脂产率可达332.8mg/(L·d)和100.2mg/(L·d),分别是对照组的3.6和3.4倍。     

镉胁迫对马蔺根系形态及部分生理指标的影响

以野生马蔺种子培育的实生苗为试验材料,采用水培法研究不同质量浓度镉(0、10、25、50、100、150 mg·L^-1)对马蔺幼苗生长、根系形态及部分生理指标的影响,分析镉胁迫下马蔺根系形态和生理指标的变化特征,以探讨马蔺的耐镉能力及耐镉机制。结果表明：(1)与对照相比,低浓度镉(10~25 mg·L^-1)促进了马蔺株高、地上部干重、根干重、总根长、根表面积、根体积和根系活力的增加,中高浓度镉(50~150 mg·L^-1)抑制根系生长,其株高、根干重、总根长等低于对照,根表面积、根体积和根系活力显著低于对照。(2)随镉浓度增加,马蔺叶片和根系中相对电导率、丙二醛(MDA)含量、过氧化物酶(POD)活性、过氧化氢酶(CAT)活性和脯氨酸(Pro)含量增加,但可溶性蛋白含量(SP)则先升高后降低;根系的超氧化物歧化酶(SOD)活性随镉浓度增加先升高后降低,而叶片SOD活性则持续增加。(3)马蔺地上部和地下部镉含量随镉离子浓度升高而增加,根系和地上部镉含量分别达到829.39~8 944.54 和200.60~519.76 mg·kg^-1,转移系数为0.06~0.32(<1.0),大多数镉离子被保留在根中,只有少量被转移到地上部。研究发现,在镉胁迫条件下,马蔺幼苗可能是通过根系对镉离子的积累,减少镉离子从根部到地上部的转移,并通过提高抗氧化酶活性、保持渗透平衡和清除过量自由基,从而提高其对镉的耐受性。     

大豆对菲胁迫的生理响应及耐菲机理研究

为了探讨菲胁迫下植物的生理反应及耐受机制,以大豆为供试材料,采用叶片喷施试验,分别从表型、生物量、氧化损伤以及抗氧化酶活性等方面研究不同浓度菲处理对大豆幼苗生长的影响。结果表明:低浓度菲(≤50 μmol/L)能够增加叶片生物量,提高叶绿素及类胡萝卜素含量。同时,幼苗叶片中的丙二醛(Malondialdehyde,MDA)含量、脯氨酸含量,超氧化物歧化酶(Superoxide dismutase,SOD)活性以及过氧化物酶(Peroxidase,POD)的活性明显高于对照组。在高浓度菲(75-100 μmol/L)处理下,MDA含量继续增大,大豆幼苗的生物量、叶绿素含量、渗透胁迫物质含量及SOD活性都受到抑制,而叶片中的类胡萝卜素含量及POD活性较高。以上结果表明,植物通过提高SOD和POD活性,以及类胡萝卜素和渗透胁迫物质含量来减轻叶片施用菲对植物生物量、叶绿素含量及氧化胁迫的影响。此外,POD和类胡萝卜素在高浓度菲胁迫下仍保持较高水平,说明它们在菲胁迫中起到较为稳定的作用。     

Physiological and biochemical analysis of mechanisms underlying cadmium tolerance and accumulation in turnip

The capacity of plants to accumulate cadmium (Cd) is significant for phytoremediation of Cd-polluted soils. Turnips cultivated in China include species featuring high Cd accumulation and some of these plants act as Cd hyperaccumulator landraces. These plants can accumulate over 100 mg Cd kg^-1 dry weight in leaves without injury. Hence, studies that explore mechanisms underlying Cd detoxification and transport in turnip plants are essential. In the present study, we compared physiological and biochemical changes in turnip leaves treated with two Cd concentrations to controls. We discovered that Cd stress significantly increased the enzymatic activities or compound contents in the antioxidant system, including members of the glutathione-ascorbic acid cycle, whereas oxidation of reactive oxygen species (ROS) remained stable. Cd treatments also increased the contents of phytochelatins as well as a number of amino acids. Based on these results, we conclude that turnips initiate a series of response processes to manage Cd treatment. First, the antioxidant system maintaining ROS homeostasis and osmotic adjustment is excited to maintain stability of cell osmotic potential. Cd is chelated into its stable form to reduce its toxicity. Cd is possibly transported to vacuoles or non-protoplasts for isolation. Amino acid synthesis may directly and indirectly play an important role in these processes. This study partly revealed physiological and biochemical mechanisms underlying turnip response to Cd stress and provides information on artificially increasing or decreasing Cd accumulation in turnips and other plants.     

Systematic investigation of biomass and lipid productivity by microalgae in photobioreactors for biodiesel application

We describe a methodology to investigate the potential of given microalgae species for biodiesel production by characterizing their productivity in terms of both biomass and lipids. A multi-step approach was used: determination of biological needs for macronutrients (nitrate, phosphate and sulphate), determination of maximum biomass productivity (the “light-limited” regime), scaling-up of biomass production in photobioreactors, including a theoretical framework to predict corresponding productivities, and investigation of how nitrate starvation protocol affects cell biochemical composition and triggers triacylglycerol (TAG) accumulation. The methodology was applied to two freshwater strains, Chlorella vulgaris and Neochloris oleoabundans, and one seawater diatom strain, Cylindrotheca closterium. The highest total lipid content was achieved with N. oleoabundans (25-37% of DW), while the highest TAG content was found in C. vulgaris (11-14% of DW). These two species showed similar TAG productivities.     

Screening of Malaysian indigenous microalgae for antioxidant properties and nutritional value

Fourteen indigenous microalgal samples from Malaysia were isolated, purified and cultured from fresh, brackish and marine waters. The ability of the microalgae to be natural sources of antioxidants was studied by a screening test using three antioxidant chemical assays [ferric thiocyanate (FTC), thiobarbituric acid (TBA) and 1, 1’-diphenyl-2-picrylhydrazyl (DPPH)]. The results showed that six microalgal methanolic crude extracts (Isochrysis galbana, Chaetoceros calcitrans, Scenedesmus quadricauda, Chlorella vulgaris, Nannochloropsis oculata and Tetraselmis tetrathele) were active in inhibiting the lipid peroxidation of linoleic acid. Among all the microalgae, I. galbana and C. calcitrans showed the highest antioxidant activity (>90%) in FTC and TBA assays, indicating that these microalgae might contain active compounds for protection from lipid peroxidation. Nutritional analyses were performed on microalgae with high antioxidant activities (I. galbana and C. calcitrans) in order to investigate their nutritive value. Both microalgae were found to be rich in nutrients. For examples, I. galbana had average percentage composition of protein, carbohydrate, and lipid, as 47.9 ± 2.5; 26.8 ± 0.2; 14.5 ± 1.4%, respectively, while the corresponding values for C. calcitrans were 36.4 ± 1.7; 27.4 ± 3.0; 15.5 ± 0.9%. In addition, they contained high levels of omega-3 polyunsatrated fatty acids (PUFA) (28.0% ± 0.7 in I. galbana and 28.5% ± 1.4 in C. calcitrans), omega-6 PUFA (6.5% ± 1.8 in I. galbana and 23.0% ± 2.5 in C. calcitrans) and a high composition of essential amino acids. This study illustrates that some microalgae such as I. galbana and C. calcitrans have the potential to be used as natural sources of antioxidants with high nutritional value. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Foliar spray of brassinosteroid enhances yield and quality of Solanum lycopersicum under cadmium stress

The presence of cadmium in the soil above a particular level is proposed to check not only plant growth but also productivity and fruit quality. Therefore, in the present study investigations are directed to evaluate the effect of four levels of cadmium (3, 6, 9, 12 mg kg⁻¹) in interaction with two analogs of brassinosteroids on the growth, fruit yield and quality of tomato. Under greenhouse conditions plants were analyzed for antioxidant system activity and photosynthetic assimilation efficiency. Cd stressed plants exhibited poor growth and biological yield. The metal also had a negative impact on the antioxidant system of the resulting fruits. However, the follow up application of BRs (10⁻⁸ M) neutralized the damaging effects of the metal on the plants.     

Physiological mechanism of hypertolerance of cadmium in Kentucky bluegrass and tall fescue: Chemical forms and tissue distribution

Kentucky bluegrass (Poa pratensis) and tall fescue (Festuca arundinacea) are hypertolerant grasses to soil cadmium contamination. Little information is available on their tolerance mechanism. A sand culture and a hydroponic culture experiment were designed to investigate the Cd chemical form changes and its translocation in different tissues. The results showed that Kentucky bluegrass and tall fescue can tolerate 50–200 mg kg⁻¹ of soil Cd stresses and accumulate as high as 4275 and 2559 mg Cd kg⁻¹ DW, respectively, in their shoots without the loss of shoot biomass. Their Cd hypertolerance was correlated with an increase of the undissolved Cd phosphates in the leaves in both grass species, as determined by sequential solvent extraction procedures. The superior Cd tolerance of tall fescue to Kentucky bluegrass was associated with less Cd translocation into the stele of roots and less Cd transported to leaves. The pectate- and protein-integrated Cd forms may be involved in the symplastic translocation of Cd from cortex into stele, and this may lead the higher Cd concentrations in the stele of roots and then above ground leaves via long-distance transport in Kentucky bluegrass.     

Zero-waste biorefinery of oleaginous microalgae as promising sources of biofuels and biochemicals through direct transesterification and acid hydrolysis

Oleaginous microalgae are considered as promising sources of biofuels and biochemicals due to their high lipid content and other high-value components such as pigments, carbohydrate and protein. This study aimed to develop an efficient biorefinery process for utilizing all of the components in oleaginous microalgae. Acetone extraction was used to recover microalgal pigments prior to processes for the other products. Microalgal lipids were converted into biodiesel (fatty acid methyl ester, FAME) through a conventional two-step process of lipid extraction followed by transesterification, and alternatively a one-step direct transesterification. The comparable FAME yields from both methods indicate the effectiveness of direct transesterification. The operating parameters for direct transesterification were optimized through response surface methodology (RSM). The maximum FAME yield of 256 g/kg-biomass was achieved when using chloroform:methanol as co-solvents for extracting and reacting reagents at 1.35:1 volumetric ratio, 70 °C reaction temperature, and 120 min reaction time. The carbohydrate content in lipid-free microalgal biomass residues (LMBRs) was subsequently acid hydrolyzed into sugars under optimized conditions from RSM. The maximum sugar yield obtained was 44.8 g/kg-LMBRs and the protein residues were recovered after hydrolysis. This biorefinery process may contribute greatly to zero-waste industrialization of microalgae based biofuels and biochemicals.     

健康老年人肠道中肠杆菌科细菌的分布及其耐药机制研究

目的分析健康老年人肠道菌群,探讨本地区健康老年人肠道中肠杆菌科细菌的分布及其耐药情况。方法取粪便标本分别接种于血平板、SS平板、麦康凯平板进行细菌培养,用全自动微生物鉴定仪和质谱仪鉴定细菌到种,采用K-B纸片扩散法进行药敏试验测定其耐药表型,PCR扩增测序再与GenBank上比对其耐药基因。结果在175例研究对象中,有59. 4%（104/175）的健康老年人肠道中只有一种肠杆菌科细菌;细菌种类以大肠埃希菌为主,占88.0%。大肠埃希菌对IPM、CTX、AMC.F0X和CIP的耐药率分别为0% ,27.9%、4. 5% ,1.3%和37. 0% ;肺炎克雷伯菌对IPM、CTX、AMC、FOX和CIP的耐药率分别为1.9%、5.8%、1.9%、1.9%和3.8%;两者相比较,大肠埃希菌对CTX、CIP的耐药率明显高于肺炎克雷伯菌（P〈0. 05）。ESBLs总携带率为17. 4%,其中大肠埃希菌的携带率（24.0%）明显高于肺炎克雷伯菌（5.8%） （P 〈0.05）;产ESBLs菌株的基因型,均为CTX-M型酶,其中以CTX-M-14最多,占57. 8%。结论本研究获得了老年人肠道肠杆菌科细菌的分布特点及其耐药机制。健康老年人肠道中肠杆菌科细菌部分抗生素的耐药率比浙江省内医院肠杆菌科细菌统计结果低,这主要是和其ESBLs携带率较低相关;但同时也已有泛耐药细菌的出现,应提高警惕。