镉吸附细菌的分离及其对土壤镉的固定

[目的] 探究镉吸附细菌是否能够高效固定土壤有效镉（Cd）,为土壤有效Cd的微生物固定提供理论依据。[方法] 利用含Cd²⁺牛肉膏蛋白胨液体培养基对细菌进行Cd的耐受性测试筛选出镉抗性强的菌株;通过16S rRNA基因相似性及系统进化分析鉴定耐镉细菌,将菌细胞加入含CdCl₂溶液中进行Cd²⁺吸附效率测定;通过土培模拟实验,测定土壤pH、碱解氮、有效磷、速效钾、有机质、CEC、有效Cd及微生物数量来分析镉吸附细菌对镉污染土壤的影响。[结果] 从德阳鱼腥草根际土壤中分离获得的57株细菌对Cd²⁺表现出不同程度的抗性,并从中筛选出3株耐Cd优势细菌普罗威登斯菌属（Providencia）DY8、芽孢杆菌属（Bacillus）DY3和芽孢杆菌属（Bacillus）DY1-4。其对溶液中的Cd²⁺表现出较好的吸附作用,吸附效率随着Cd²⁺浓度升高而降低。DY8、DY3、DY1-4能使镉污染土壤中有效Cd含量分别降低72.11%、68.55%、62.32%,同时显著提高镉污染土壤中碱解氮、有效磷的含量。[结论] Cd污染农田土壤中含有丰富的耐Cd微生物资源,Cd吸附细菌能降低土壤中有效Cd的含量,且能有效改善土壤养分条件。     

不同恢复阶段热带森林土壤nirS型反硝化微生物群落结构及多样性特征

探明热带森林土壤反硝化微生物群落结构及多样性，对于理解反硝化引起的N₂O排放及缓解全球变暖具有重要意义。本研究以西双版纳3个不同恢复阶段热带森林类型[即白背桐（Mallotus paniculatus，MP）、崖豆藤（Millttia leptobotrya，ML）群落、群落及高檐蒲桃（Syzygium oblatum，SO）群落]为研究对象，揭示土壤nirS型反硝化微生物群落组成及多样性的干湿季变化，分析热带森林恢复过程中土壤理化环境变化对nirS型反硝化细菌群落的影响。结果表明，变形菌门（Proteobacteria）和酸杆菌门（Acidobacteria）相对丰度表现为恢复前期高于恢复后期，而脱氯单胞菌属（Dechloromonas）、嗜盐单胞菌属（Halomonas）和罗思河小杆菌属（Rhodanobacter）表现为恢复后期高于恢复前期；绿弯菌门（Chloroflexi）和放线菌门（Actinobacteria）均随恢复年限增加而增加，而贪铜菌属（Cupriavidus）和假单胞菌属（Pseudomonas）的相对丰度表现为随恢复年限增加而降低。9月份各样地新检测出的属数量表现为：SO （19种） > MP （13种） > ML （7种）。土壤nirS型反硝化微生物群落的Shannon多样性指数表现为：高檐蒲桃群落 > 崖豆藤群落 > 白背桐群落，且9月（湿季） > 3月（干季）。相关分析表明，热带森林恢复引起土壤N库（全氮、NH₄⁺、NO₃^-）、C有效性（微生物量碳、易氧化碳）及微气候（土壤含水率与温度）的改变，能够显著影响nirS型反硝化细菌群落的结构及多样性。主成分分析结果表明，土壤硝态氮、微生物量碳、全氮及易氧化碳是调控不同恢复阶段热带森林土壤nirS型反硝化细菌群落结构及多样性变化的主控因子，其次为土壤水分、温度、水解氮、pH、铵态氮、有机碳、容重及C/N。     

617株耐亚胺培南铜绿假单胞菌耐药性及其产超广谱β-内酰胺酶基因型研究

探讨耐亚胺培南铜绿假单胞菌的耐药性及其产超广谱β-内酰胺酶基因型。收集2011年7月至2013年12月上海市中医药大学附属曙光医院临床分离的铜绿假单胞菌共1 125株,筛选亚胺培南耐药株,常规纸片法检测其耐药性,并用E-test检测金属β-内酰胺酶（MBL）,采用PCR法检测耐药基因型。结果显示,1 125株铜绿假单胞菌中耐亚胺培南铜绿假单胞菌共计617株,占54.8%;亚胺培南敏感铜绿假单胞菌共计508株,占45.2%。617株亚胺培南耐药铜绿假单胞菌100%为多重耐药,而亚胺培南敏感铜绿假单胞菌的多重耐药率仅为13.78%,明显较前者低（χ²=871.15,P<0.05）;亚胺培南耐药的铜绿假单胞菌中MBL表型阳性共126株,阳性率为15.4%,94株(74.60%)表现为VIM-2阳性,10株（7.94%）表现为IMP-1阳性,1株检出OXA-10,〖WTBZ〗且该例菌株同时表达VIM-2。临床分离的耐亚胺培南的铜绿假单胞菌多为多重耐药,其产MBL的主要基因型是VIM-2。     

生物炭对褐土旱地玉米季氮转化功能基因、丛枝菌根真菌及N2O释放的影响

以豫西旱地玉米农田为研究对象,设置不同生物炭施用量处理（T0：不施用生物炭;T1：施用生物炭20 t/hm²;T2：施用生物炭40 t/hm²）,采用密闭式静态箱法测定N₂O排放通量和荧光定量PCR法分析丛枝菌根（arbuscular mycorrhizal,AM）真菌、氨单加氧酶（amoA）、亚硝酸盐还原酶（nirS、nirK）以及氧化亚氮还原酶（nosZ）的基因丰度,同时测定土壤理化性状的变化。研究结果表明,随着生物炭施用量的增加,土壤pH和含水量呈增加趋势,土壤有机碳、全氮和铵态氮含量显著提高,土壤容重和硝态氮含量显著降低。T1和T2处理土壤有机碳含量分别较T0显著提高38.44%和71.01%;T1和T2处理土壤铵态氮含量分别较T0显著增加15.89%和30.46%;T2处理土壤全氮含量较T0处理显著提高14.87%;T1和T2处理土壤硝态氮含量分别较T0减少10.57%和21.40%。随着生物炭施用量的增加,AM真菌侵染率显著增加,T1和T2处理分别较T0处理提高71.88%和115.88%;AOA、AOB、nirK和nirS基因丰度显著降低;nosZ基因丰度增加。施加生物炭处理的N₂O排放通量和累积排放量均低于不施生物炭处理,具体表现为：T0 > T1 > T2。相关分析表明,生物炭施用量与AM真菌基因丰度呈显著正相关;与nosZ基因丰度呈正相关;与AOA、AOB、nirK、nirS基因丰度呈极显著负相关。N₂O排放通量与AOA、nirK、nirS基因丰度呈极显著正相关;与土壤含水量和土壤硝态氮含量呈显著正相关;与AM真菌、nosZ基因丰度、易提取球囊霉素含量、铵态氮含量呈极显著负相关。集成推进树（ABT）分析表明,AOA对N₂O排放的影响最大,其次是AM真菌和nirS。总之,生物炭处理改善土壤理化性质、提高土壤AM真菌侵染率、调节硝化、反硝化相关功能基因的丰度,减少N₂O气体排放,为旱地农田合理施用生物炭减少N₂O气体排放提供理论依据。     

抑制铜绿假单胞菌和金黄色葡萄球菌生物膜形成的乳杆菌筛选及机制初探

筛选得到对慢性创面中铜绿假单胞菌（Pseudomonas aeruginosa）和金黄色葡萄球菌(Staphylococcus aureus)生物膜形成具有抑制作用的乳杆菌(Loctobacillus)。测定不同种乳杆菌对铜绿假单胞菌和金黄色葡萄球菌双菌生物膜量、生长及群体感应信号分子AI-2的影响，并采用主成分分析和菌株特性综合分析确定效果最佳的菌株，最后通过荧光定量PCR的方式探究该菌株对生物膜和群体感应相关基因表达的影响。结果表明，植物乳杆菌(Lactobacillus plantarum)、卷曲乳杆菌(Loctobacillus crispatus)、嗜酸乳杆菌(Loctobacillus acidophilus)、鼠李糖乳杆菌(Loctobacillus rhamnosus)、瑞士乳杆菌(Loctobacillus helveticus)、短乳杆菌(Loctobacilkus brevis)具有不同程度的抑菌、抑制生物膜形成的能力，且同种不同株的乳杆菌抑制生物膜形成的能力也有所差异。其中，植物乳杆菌CCFM233产生的AI-2信号分子较多，具有良好的抑菌能力，可使致病菌生物膜形成量降低，铜绿假单胞菌的LasR和rhlI基因表达水平和金黄色葡萄球菌的SarA基因表达水平显著下调。本研究旨在揭示植物乳杆菌CCFM233具有抗铜绿假单胞菌和金黄色葡萄球菌感染的潜力，为其应用于慢性创面敷料提供参考。     

冬小麦免耕覆盖与生物有机肥施用对土壤细菌群落的影响

为揭示保护性耕作措施对土壤细菌群落结构及多样性的影响规律,选取免耕覆盖＋施生物有机肥（NF）、免耕覆盖＋不施生物有机肥（NC）、传统耕作不覆盖＋施生物有机肥（TF）和传统耕作不覆盖＋不施生物有机肥（TC）4个处理,以农田土壤生态系统为研究对象,利用16S rDNA基因Illumina MiSeq高通量测序技术,研究了冬小麦免耕覆盖与生物有机肥施用对土壤细菌群落结构及多样性的影响。结果表明：1）与TC处理相比,NF处理显著降低了土壤pH （P=0.03^*）,增加了土壤全氮（P=0.002^**）、总碳含量（P=0.0001^**,P=0.007^**）,影响了土壤碳/氮比分配（P=0.003^**）。2）从16个土壤样本中共获得细菌27门、86纲、125目、213科和315属,其中放线菌门（Actinobacteria）、酸杆菌门（Acidobacteria）、绿弯菌门（Chloroflexi）和变形菌门（Proteobacteria）为优势菌门,其相对丰度约占总丰度的82.40%。3）与传统耕作施生物有机肥处理相比,免耕覆盖施生物有机肥增加了土壤细菌的多样性指数（Simpson指数和Shannon指数）,降低了ACE丰富度指数。4）NMDS及多元分析结果表明：土壤细菌群落丰富度指数、多样性指数均与土壤pH、速效磷和土壤碳/氮比成正相关,与土壤微生物生物量碳（SMBC）和土壤总碳成负相关;其中,土壤pH和SMBC分别是影响酸杆菌门和放线菌门的主要驱动因子。施生物有机肥和耕作措施两种因素均对土壤细菌群落结构组成产生了影响,但以施用生物有机肥对土壤细菌群落多样性的影响较明显;此外,施用生物有机肥在传统耕作和免耕覆盖两种情况下均增加了冬小麦产量,但以传统耕作施生物有机肥处理最明显。因此,传统耕作配施生物有机肥是宁夏南部山区改善土壤理化性质、增加土壤细菌群落丰富度和多样性的重要途径。     

微生物菌肥对寒地大豆根围土壤细菌群落和产量的影响

通过施用微生物菌肥研究寒地大豆根围土壤细菌多样性和群落组成,缓解因长期施用化肥和农药带来的土壤问题。以大豆合农69为研究对象,设置6个处理：施用大豆专用肥、颗粒肥、复合菌肥、减施15%化肥配施颗粒肥、减施15%化肥配施微生物复合颗粒肥和空白对照,采用高通量测序技术分析大豆荚期根围土壤细菌多样性和群落组成;采用传统统计学方法对株高、荚数、粒数和产量进行统计。门水平放线菌门(Actinobacteria)、变形菌门（Proteobacteria）、酸杆菌门（Acidobacteria）、绿弯菌门（Chloroflexi）、芽单胞菌门（Gemmatimonadetes）、拟杆菌门（Bacteroidetes）、Patescibacteria和WPS-2为优势菌门。其中减施15%化肥配施颗粒肥处理的优势菌门为变形菌门,其他几个处理的优势菌门为放线菌门;目、科和属水平Gaiellales/Other、酸杆菌目（Acidobacteriales/Other）、Frankiales/Other、鞘脂单胞菌属（Sphingomonas）、嗜酸栖热菌属（Acidothermus）、芽单胞菌属（Gemmatimonas）、罗河杆菌属（Rhodanobacter）、根瘤菌属（Bradyrhizobium）、芽单胞菌科（Gemmatimonadaceae/Other）、链霉菌属（Streptomyces）、念珠菌固体杆菌属（Candidatus Solibacter）、黄杆菌科（Xanthobacteraceae/Other）、褚氏杆菌属（Chujaibacter）、AD3/Other、WPS-2/Other、Saccharimonadales/Other、IMCC26256/Other、Ellin6067、Jatrophihabitans、SC-I-84/Other、芽生球菌属（Blastococcus）、苔藓杆菌目（Bryobacter）、Haliangium、Micropepsaceae/Other、锥杆菌属（Conexibacter）和Elsterales/Other共26个优势属;其中褚氏杆菌属是减施15%化肥配施福尔太微生物颗粒剂处理的优势属,酸杆菌目（Acidobacteriales/other）是空白对照优势目,Gaiellales/Other是其他4种处理的优势属。减施化肥配施福尔太微生物颗粒剂可以有效保证大豆产量,比单施化肥产量提高了4.72%。微生物菌肥的不同施肥方式可以有效改善大豆根围土壤微生物群落构成,减施化肥配施微生物菌肥对寒地大豆具有保产增产作用。     

多株功能菌种混合培养条件的响应面优化及其生长关系

对3种具有土壤中多种重金属污染修复和病虫害防治功能的光合细菌（Photosynthetic bacteria,PSB,包括Rhodobacter sphaeroides H菌株、Rhodopseudomonas palustris N菌株和Rhodospirillium rubrum M菌株）、枯草芽胞杆菌（Bacillus subtilis, BS）和植物乳酸杆菌（Lactobacillus plantarum, LP）进行混合培养,利用单因素和响应面试验优化培养基配方以及培养条件。确定功能菌混合培养的最佳条件：以光合细菌培养基为基础培养基,外加碳源为10 g/L蔗糖、氮源为1.25 g/L硫酸铵、培养温度为31.5 ℃、初始pH值为7.1、接种量为接种后的初始培养活菌数1.90×10⁹cfu/mL、培养时间为28.0 h。通过功能菌的加性模型法、生长动力学以及混合培养的生长关系分析表明,光合细菌、枯草芽胞杆菌和植物乳酸杆菌的生长均存在互惠互利关系。     

烟草根际可培养微生物多样性及防病促生菌的筛选

[背景] 根际微生物在植物根部生态系统中扮演着重要角色,影响着植物的营养吸收和健康生长。[目的] 了解常年不发病烟田烤烟品种K326根际可培养微生物的多样性,筛选具有防病促生功能的菌株,为烟草病害绿色防控提供资源。[方法] 采用传统培养方法对烟草根际土壤中的细菌和真菌进行分离鉴定,评价菌株的促生特性及病原菌拮抗能力,并进一步验证典型菌株对盆栽烟苗的促生效果。[结果] 共获得261株微生物菌株,包括160株细菌和101株真菌。经分子鉴定,细菌中以变形菌门（Proteobacteria）和厚壁菌门（Firmicutes）为主要类群;真菌中以子囊菌门（Ascomycota）和毛霉菌门（Mucoromycota）为主要类群。在属水平上,细菌以假单胞菌属（Pseudomonas）和芽孢杆菌属（Bacillus）为主,真菌以曲霉属（Aspergillus）和青霉属（Penicillium）为主。从不同种水平上进一步选择44株细菌为代表菌株,发现它们均具有不同程度的吲哚-3-乙酸（Indole-3-Acetic Acid,IAA）产生能力,9株能够溶解有机磷,16株能够溶解无机磷,13株产生铁载体,14株产生生1-氨基环丙烷-1-羧酸（1-Aminocyclopropane-1-Carboxylate,ACC）脱氨酶。从160株细菌中筛选得到抑制青枯病菌和黑胫病菌的菌株数目分别为25、26株。经盆栽试验发现韩国假单胞菌（P. koreensis） HCH2-3、浅黄绿假单胞菌（P. lurida） FGD5-2和贝莱斯芽孢杆菌（B. velezensis） EM-1对烟苗呈现不同程度的促生作用,其中3株菌联合施加对烟苗的促生效果最明显。[结论] 烟草根际存在着丰富多样的具有防病促生潜力的微生物,并且合成菌群或功能互补的菌株联合施用是未来微生物菌剂研发的重要方向。     

低温环境中T-2毒素降解菌的分离鉴定及特性研究

离筛选低温环境中T-2毒素的降解菌并探明其生化特性,探究T-2毒素降解微生物生化特性异同点,为T-2毒素降解微生物的检验提供生化判断参考。针对暴露于－20 ℃低温环境中的低浓度T-2毒素标准品,采用LC-MS/MS定量分析T-2毒素残留量,利用营养琼脂培养基（NA）和马铃薯葡萄糖琼脂培养基（PDA）共分离出5株降解菌,16S rDNA结合生化鉴定结果为死谷芽胞杆菌（Bacillus vallismortis）、蜡状芽胞杆菌（Bacillus cereus）、阴沟肠杆菌（Enterobacter cloacae）、弯曲假单胞菌（Pseudomonas geniculata）和尼泊尔葡萄球菌（Staphylococcus nepalensis）。这些分离株在－20 ℃条件下对低浓度T-2毒素均有不同程度的降解能力,其中蜡状芽胞杆菌（Bacillus cereus）降解能力最强,降解率为91%。它们的理化特性具有很多相似性,主要表现在5株菌均不能利用D 塔格糖(dTAG）,对ELLMAN都表现出阴性;Bacillus vallismortis Bp1234-7、Pseudomonas geniculata Bp24-4、〖WTBX〗Staphylococcus nepalensis Bp124-5和Enterobacter cloacae Bp123-7都能分解D-葡萄糖,而Bacillus cereus Bp1234-8不能。     

Root exudates and plant secondary metabolites of different plants enhance polychlorinated biphenyl degradation by rhizobacteria

Polychlorinated biphenyls (PCBs) are toxic and persistent compounds that are difficult to break down and biodegrade. Plant secondary metabolites (PSMs) on root exudates can act as inducers of the biphenyl catabolic pathway, enhancing PCB biodegradation. In this study, the authors evaluated the effect of root exudates and PSMs obtained from Avena sativa, Brachiaria decumbens, Medicago sativa, and Brassica juncea on the biodegradation of PCB 44, PCB 66, PCB 118, PCB 138, PCB 153, PCB 170, and PCB 180 by a microbial consortium isolated from the rhizosphere of plants grown on soil contaminated with Aroclor 1260. Microorganisms were identified as Pseudomonas sp. and Stenotrophomonas sp. based on their 16S rRNA sequence. The plant root exudates increased the degradation percentage of PCB 44, PCB 66, and PCB 118, which were used as carbon source by the microorganisms. Flavanone, flavone, isoflavone, 7-hydroxyflavanone, 7-hydroxyflavone, and 6-hydroxyflavone were the PSMs identified in the root exudates, which increased the degradation percentage of all seven PCB congeners; they were also used as growth substrates by microbial consortium. These results showed the importance of the interaction between plants and microorganisms for achieving the removal of persistent pollutants such as PCBs from soil.     

Studies on the Lipoprotein Lipases of Microorganisms

About 2000 strains of microorganisms were examined for lipoprotein lipase producibilities and some microorganisms were found to produce lipases similar to animal lipoprotein lipases.

Microorganisms were cultured on solid media containing a serum-activated olive oil emulsion, and strains which formed a clear zone around the colony were collected. The collected microorganisms were cultured on liquid media containing 0.5% of olive oil by shaking and the culture filtrates were tested for lipoprotein lipase activity by a turbidity method. The superior lipoprotein lipase producers obtained belonged to genera of Serratia, Pseudomonas, Mucor, and Streptomyces.     

Isolation of a microbial consortium from activated sludge for the biological treatment of food waste

The bacterial community in the activated sludge of a local wastewater treatment plant was studied in an effort to understand and exploit the metabolic versatility of microorganisms for the efficient biological treatment of food waste. Microorganisms capable of and efficient in degrading domestic food waste were screened based on their ability to produce areas of clearing on selective media containing protein, fat, cellulose and starch. Nine microbial species belonging to the genera Flavobacterium, Pseudomonas, Micrococcus, Aeromonas, Xanthomonas, Vibrio and Sphingomonas were found to degrade all components of food waste. These bacteria were added to domestic wastewater and shown to cause a 60% reduction in the biochemical oxygen demand (BOD) level of wastewater compared to a control in which no microorganisms were added. The ability of the microbial consortium to degrade domestic wastewater as evidenced by the decrease in BOD levels suggests its potential for use in the biological treatment of food waste.     

The Bioadsorption of Cadmium and Lead by Bacteria in Root Exudates Culture

Microorganisms are important for phytoremediation of soil contaminated with heavy metals. In the present study, bacteria Bacillus sp., Pseudomonas sp., Alcaligenes sp., and Flavobacterium sp. isolated from the Zhangshi Irrigation Area were applied to bioadsorbed Cd and Pb in liquid cultures with root exudates of sunflower as a sole carbon source. The experimental data demonstrated that these bacteria had a high potential of enrichment of Cd and Pb, and Bacillus sp. and Alcaligenes sp. had better ability to accumulate Cd or Pb than the others; the distinct bioadsorption of Cd and Pb by bacteria might depend on the physiology of bacteria, categories of heavy metals, and environmental factors (such as pH). In addition, root exudates of sunflower could not only support the growth of these bacteria, but also influence the toxicity and bioavailability of Cd and Pb. Our results indicated that amendment with bacteria isolated from heavy-metal-polluted soil and root exudates could be considered as a potential approach to enhance the phytoremediation of Cd- or Pb-contaminated soil.     

Effect of alginate encapsulation and selected disinfectants on survival of and phenanthrene mineralization byPseudomonas sp UG14Lr in creosote-contaminated soil

The survival and phenanthrene-mineralizing ability of free and alginate-encapsulatedPseudomonas sp UG14Lr cells were examined in a creosote-contaminated soil. Alginate encapsulation adversely affected both survival and phenanthrene mineralization. This was postulated to be due to concentration of water-soluble toxic compounds in the alginate beads. Toxicity studies showed that the concentrated water-soluble fraction of the creosote-contaminated soil may be toxic toPseudomonas sp UG14Lr in soil with a low moisture content. Survival of alginate-encapsulated cells improved with increasing soil moisture content. Free cells survived well at a steady population of 10⁸ CFU g^–1 dry soil for 28 days in the creosote-contaminated soil. However, phenanthrene mineralization was not improved compared to the uninoculated control. This was attributed to the existence of indigenous phenanthrene-mineralizing microorganisms already present in this contaminated soil. The effect of calcium hypochlorite and Germiphene on survival of and phenanthrene mineralization by free and alginate-encapsulatedPseudomonas sp UG14Lr cells in creosote-contaminated soil was also studied. Addition of 0.1% (w/w dry soil) calcium hypochlorite reduced the introduced free cells to below detection limits (10 CFU g^–1 dry soil) within 14 days, while Germiphene had no effect on cell numbers. Phenanthrene mineralization by free cells was not adversely affected by treatment with calcium hypochlorite or Germiphene. Survival of alginate-encapsulated cells after treatment with disinfectants was as poor as that without disinfection. The results show that alginate encapsulation may not be a suitable formulation for introduction ofPseudomonas sp UG14Lr into creosote-contaminated soils.     

Adsorption,Bioavailability, and Toxicity of Cadmium to Soil Microorganisms

The influence of adsorption on cadmium toxicity to soil microorganisms in soils was quantified as a function of solution and sorbent characteristics. The influence of adsorption on cadmium toxicity to soil microorganisms was assessed indirectly through the relative change in microbial hydrolysis of fluorescein diacetate (FDA) as a function of total Cd concentration and sorbent characteristics. The sequence of relative percentage of FDA hydrolysis was reference smectite (RS) > untreated Vertisol (UV) > dithionate-citrate-bicarbonate (DCB)-treated Vertisol (DV) > H₂O₂-treated Vertisol (HV) in suspensions containing the same total Cd concentrations. The correlation between the percentage of FDA hydrolysis and activity of Cd²⁺ _(aq) illustrates that RS has a higher capacity of Cd adsorption. The microbial activity of RS was higher and the toxicity was lower than that of other soil samples. The HV had lower capacity of Cd adsorption so that its FDA hydrolysis was low and the Cd toxicity was high.     

Co-inoculation Effects of Rhizobium sullae and Pseudomonas sp. on Growth,Antioxidant Status,and Expression Pattern of Genes Associated with Heavy Metal Tolerance and Accumulation of Cadmium in Sulla coronaria

Recently, phytoremediation assisted by soil bacteria has emerged as a potential tool to clean up the metal-contaminated/polluted environment. Three plant-growth-promoting bacteria (PGPBs): Rhizobium sullae, Pseudomonas fluorescens, and Pseudomonas sp. were found to tolerate cadmium (Cd) stress. Sulla coronaria inoculated with these PGPBs, and grown under different Cd concentrations (0, 100, and 200 µM), showed increases in dry biomass and proline content. Notable increases in different gas-exchange characteristics such as photosynthesis rate (A), transpiration rate (E), and water-use efficiency (WUE), as well as increases in nitrogen (N) and Cd accumulations were also recorded in inoculated plants compared to non-inoculated Cd stressed plants. The activities of antioxidant enzymes superoxide dismutase (SOD), guaiacol peroxidase (GPOX), catalase (CAT), and ascorbate peroxidase (APX) in S. coronaria roots increased under Cd stress after PGPB co-inoculation, suggesting that these PGPB species could be used for amelioration of stress tolerance in S. coronaria. The expression patterns of ScPCS, ScMT, ScF-box, ScGR, and ScGST in roots of S. coronaria indicated that these genes are differentially expressed under Cd treatments, suggesting their possible roles in Cd and heavy metal stress responses. The results indicate that co-inoculation with R. sullae and Pseudomonas sp. could alleviate Cd toxicity in S. coronaria. In the present study, the obtained data suggest that the application of PGPBs could be a promising strategy for enhancing the phytostabilization efficiency of Cd-contaminated soils.

     

Microbial Production of Theobromine from Caffeine

Production of theobromine from caffeine by caffeine-degrading bacteria was studied. We found that addition of metal ions such as Zn²⁺ to intact cells of a caffeine-degrading isolate from soil, Pseudomonas sp. No.6, resulted in a high theobromine accumulation from caffeine. We hypothesized that Zn²⁺ acts as a selective inhibitor of one of the theobromine-demethylating enzymes and further screened for theobromine-producing activities in the presence of Zn²⁺ among a number of caffeine-using microorganisms. A strain identified taxonomically as Pseudomonas putida No. 352 showed the best productivity among 973 microorganisms of stock cultures and soil isolates. Culture conditions for the production of theobromine from caffeine by P. putida No. 352 were studied. Under optimal conditions, nearly 20 g/liter of theobromine was produced from caffeine in a yield of 92%.     

碱性土壤盐化过程中阴离子对土壤中镉有效态和植物吸收镉的影响

镉是土壤环境中对土壤质量有着极其重要影响的污染物之一,低含量下就能对人体和动物产生危害.镉在土壤中的有效态既决定了它的生物有效性及对环境的危害程度,又是人们对受污染土壤进行治理和修复的基础.作为盐化土壤中的典型组分,无机盐不可避免对镉的有效态及生物有效性等地球化学行为产生明显影响.研究了碱性土壤盐化过程中无机盐阴离子对土壤中镉有效态和植物吸收镉影响.研究方法为:以钠盐为例,实验研究了碱性土壤盐化过程中无机盐阴离子对土壤中镉有效态的影响;通过油菜种植试验,分析了无机盐阴离子对土壤中镉生物有效性的影响.研究结果表明,土壤盐化过程中,土壤溶液中Cl-浓度较低时,土壤中镉的有效态含量随Cl-浓度增加而增大,但当土壤中Cl-/Cd的比值大于100∶1时,土壤中镉的有效态含量达到最大值.土壤溶液中SO42-含量对土壤中镉有效态含量的影响不明显;随着土壤溶液中HCO3-含量的增加,土壤中镉的有效态含量明显减少.由于Cl-、SO42-是土壤溶液中的主要成分,随着盐度的增加,镉的有效态含量增加.油菜种植试验显示,当土壤中Cl-的含量增加时,土壤中镉的有效态含量增加,有利于植物对镉的吸收,因此油菜中镉的含量随土壤中Cl-的含量增加而增加,但当土壤有效态含量超过2 mg/kg后,油菜吸收镉已经达到最大.随着土壤溶液中SO42-浓度的增加,油菜中镉含量基本不变;土壤溶液中HCO3-的含量增加,植物中镉的含量随土壤中HCO3-含量增加而减少.这些特征与土壤镉有效态变化相吻合.通过各种措施控制土壤盐度和调节阴离子类型和含量,有利于降低土壤中镉的有效态含量,减轻镉的活化;农业生产中适当调整无机肥料的种类,可以减少农作物对镉的吸收.     

Conversion of Lesquerolic Acid to 14-Oxo-11(<Emphasis Type="Italic">Z</Emphasis>)-Eicosenoic Acid by Genetically Variable <Emphasis Type="Italic">Sphingobacterium multivorum</Emphasis> Strains

This study focuses on the isolation and characterization of a high cadmium (Cd)-resistant bacterial strain, and possible exploitation of its Cd-accumulation and Cd-induced siderophore production property to improve plant growth in cadmium-contaminated soil through root colonization. The bacterial strain could tolerate up to 8 mM of Cd and could accumulate Cd intracellularly. The strain showed Cd-induced siderophore production maximally at 1.75 mM of Cd concentration under culture condition. It stimulated the growth of mustard and pumpkin plants in Cd-added soil through its establishment in rhizosphere. Through biochemical characterization and 16S rDNA sequence analysis, the strain KUCd1, as the name given to it, was identified as a strain of Pseudomonas aeruginosa.