酸性土壤中耐铝细菌的筛选鉴定及其耐铝能力分析

以含有1 mmol/L Al3+的S-LB培养基作为筛选培养基,从酸性土壤中分离到13株耐铝的细菌菌株,选取其中6株进行形态学分析,结果观察到这些菌株的菌体均呈杆状,其中1株为革兰阳性反应,其余5株为革兰阴性反应。以细菌通用引物扩增这些菌株的16S rDNA并测序,将得到的序列与GenBank中的序列进行BLAST比对,利用MEGA 4.0软件,按照Neighbor-joining法构建系统进化树,这6个菌株分别与Enterobacter endosymbiont、Serratia marces-cens、Pantoea agglomerans、Enterobacter aerogenes、Bacillus subtilis和Enterobacter asburiae的亲缘关系最近。将这些菌株接种到加有2 mmol/L Al3+、pH 4.5的S-LB固体培养基上培养时,它们都能生长,说明这些菌株具有较好的耐铝能力,这些菌株为进一步研究细菌的耐铝机制提供了极好的材料。

不同决明品种(系)的耐铝毒能力研究

在铝浓度60 mg/L下,对10个不同决明品种(系)进行液培。通过农艺性状、主根伸长率、株高增长率、根系电导率、根系活力和脯氨酸含量变化测定,研究不同决明牧草品系的耐铝毒能力。试验结果表明,86134R2、86134R1、86134R3、2204、92985R1属于耐铝毒的决明品种(系);34721R1、34721R2、34721F4、92985R2决明品种(系)耐铝毒能力中等;34721F7属于铝敏感决明品系。

一株耐铝甜瓜枯萎病拮抗细菌的分离鉴定及其耐铝特性研究

从甜瓜根际酸性土壤中分离筛选到1株耐铝甜瓜枯萎病拮抗菌,命名为A2。根据表型、生理生化特征和16S r RNA基因序列相似性分析,将其鉴定为Pseudomonas sp.。菌株A2对甜瓜枯萎病病原菌的相对防效为68.3%,且拮抗能力具有遗传稳定性。相比Al Cl3处理,菌株A2对Al2(SO4)3表现出了更好的耐受性,最高可耐受50mmol/L Al3+。在含有A13+的S-LB培养基中,菌株最适生长温度为30℃;培养基初始p H值的降低会加剧A13+对菌株A2的毒害作用。研究结果可为含活性铝的酸性土壤中甜瓜枯萎病的生物防治提供优良菌株资源和理论基础。

海南五指山茶园土壤中耐铝细菌的分离鉴定及其耐铝特性

从海南五指山茶园土壤中分离得到2株高效耐铝细菌,命名为A3、 A4。根据表型、生理生化特性和16S rRNA基因序列相似性分析,将其分别鉴定为不动杆菌属(Acinetobacter sp.)、短波单胞菌属(Brevundimonas sp.)。A3可耐受12 mmol/L Al^(3+),菌株A4最高可耐受20 mmol/L Al^(3+)。选取耐铝效果较好的菌株A4,进一步研究其在不同浓度Al^(3+)(0、 10、 20 mmol/L)下的生长规律。发现菌株A4在Al^(3+)存在条件下, pH为4.5～5.0时,对培养基起始pH的变化并不敏感;菌株A4的耐铝能力并不受Al^(3+)诱导而变化,是其本身的固有特性。试验结果可为耐铝细菌改良酸性土壤提供良好的菌种资源。

铝胁迫对决明属水土保持牧草幼苗根系的影响

耐铝能力对红、黄壤山区水土保持牧草的生长具有重要影响。AFT2 2 17(C .nictitans)、CPI3 472 1(C .rotundi folia)和CPI8613 4(C .rotundifolia)三个决明品系水土保持牧草耐铝能力均较强 ,但对Al3+ 敏感性有差异 ,按反应强弱排序为 :CPI8613 4>AFT2 2 17>CPI3 472 1;经 6个Al浓度梯度处理 ,从主根长、侧根数、根细胞质膜透性等指标分析 ,三个决明品系中CPI3 472 1的幼苗耐铝能力相对较强 ,AFT2 2 17、CPI8613 4耐铝能力稍弱 ,铝毒临界值前者为 60mg/L ,后两者为 40mg/L。同时试验表明决明品系水土保持牧草的根系需要适量铝的刺激 。

铝胁迫下八仙花HmVALT基因表达的差异

【目的】了解八仙花HmVALT基因表达与耐铝能力的关系,揭示八仙花耐铝机理。【方法】以耐铝的八仙花品种H.macrophyllacv‘Coerulea’为材料,扩增获得HmVALT基因片段,利用半定量RT-PCR方法,分析在0,50,100,200,400,600μmol/L AlCl3胁迫下,八仙花根和叶中HmVALT基因的表达情况。【结果】各处理HmVALT基因在八仙花根和叶部均有表达,且根部的表达量高于叶部;铝胁迫浓度为400μmol/L时八仙花根和叶中HmVALT基因表达量最高,随后降低。【结论】HmVALT基因的表达与八仙花耐铝性密切相关。

E2EM’s prediction of LaB_(6) as nucleation substrate for primary Mn-rich phase in Al-Si-Cu-Mn heat-resistant alloy and its refining effect

Edge-to-edge matching(E2EM)model was used to predict the potency of LaB_(6) as the heterogeneous nucleation substrate for primary Al_(13)Mn_(4)Si_(8) phase formed during the solidification of Al−Si−Cu−Mn heat-resistant alloy.There are five pairs of orientation relationships(ORs)between LaB_(6) and Al_(13)Mn_(4)Si_(8) phases which meet the criteria of E2EM model.One pair of plane ORs((110)LaB_(6)//(110)Al_(13)Mn_(4)Si_(8))are demonstrated by TEM observation.This strongly indicates that the LaB_(6) phase can act as the heterogeneous nucleation substrate for the primary Al_(13)Mn_(4)Si_(8) phase.1.0 wt.%of Al−2La−1B master alloy was also added into Al−12Si−4Cu−2Mn alloy to evaluate the refining effect by microstructure observation and tensile test.Experimental results show that addition of Al−2La−1B master alloy can significantly refine the primary Al_(13)Mn_(4)Si_(8) phase,supporting the prediction accuracy of E2EM model.However,such refinement of primary Al_(13)Mn_(4)Si_(8) phase does not lead to an improvement in strength.This is due to the larger difference in elastic modulus between the finally formed Al_(13)Mn_(4)Si_(8) phase and aluminum matrix than that of Al_(15)Mn_(3)Si_(2) phase.

Enhancing mechanical properties and corrosion performance of AA6063 aluminum alloys through constrained groove pressing technique

The use of a constrained groove pressing(CGP) method to plastically deform AA6063 aluminum alloy led to the improved surface properties. It was found that hardness magnitude is dramatically improved and its uniformity is considerably decreased after the first pass, while subsequent passes result in better hardness behavior for the processed material. Also, the elongated grains formed in the first pass of the CGP are gradually converted to the equiaxed counterparts by adding pass numbers. Eventually, higher corrosion resistance of the sample by imposing the CGP process is related to the quick formation of passivation film and the change in the morphology of the second phase and precipitates which hinder their electrochemical reactions and decrease the potential localized attack sites.