Root endophytes enhance stress‐tolerance of Cicuta virosa L. growing in a mining pond of eastern Japan

Cicuta virosa L. plants can grow in a pond subjected to heavy‐metal inputs at the Hitachi mine, eastern Japan. They accumulate heavy‐metal elements, especially high concentrations of zinc (Zn), in their roots. We focused on the role that root bacterial endophytes play in the heavy‐metal uptake of plants and the provision of heavy‐metal tolerance within plants. Our purpose was to clarify the effects of endophytes on: (i) Zn accumulation in C. virosa roots; (ii) growth of C. virosa seedlings; and (iii) heavy‐metal tolerance of C. virosa plants. Root endophytic Pseudomonas putida and Rhodopseudomonas sp., which induced the high production of Zn‐chelating compounds, were selected for the seedling inoculation test. The results of the inoculation test demonstrated that both strains of endophytes increased Zn accumulation in C. virosa roots by solubilizing Zn in the sediment. Both strains also increased the growth of seedlings by possible production of indole‐3‐acetic acid in the plant. The heavy‐metal tolerance of C. virosa seedlings was likely promoted by producing metal‐chelating compounds that detoxify the metals in the plant tissues, and by decreasing the heavy‐metal contents in the tissues via rapid seedling growth. Thus, such mutualistic interactions between plants and bacteria contribute to the persistence of C. virosa in this severe environment.     

Enhancement of the efficiency of Cd phytoextraction using bacterial endophytes isolated from Chromolaena odorata,a Cd hyperaccumulator

Phytoextraction is a technique using a hyperaccumulator to remove heavy metals from soil. The efficiency of heavy metal uptake can be enhanced by the inoculation of endophytes. In this study, we isolated and identified 23 endophytes from Chromolaena odorata, a cadmium (Cd) hyperaccumulator that consisted of 19 bacteria, 2 actinomycetes and 2 fungi. All bacteria and fungi could produce at least 1 plant growth promoting factors. However, only 4 bacterial isolates; Paenibacillus sp. SB12, Bacillus sp. SB31, Bacillus sp. LB51, and Alcaligenes sp. RB54 showed the highest minimum inhibitory concentration (MIC) value (2.9 mM), followed by Exiguobacterium sp.RB51 (1.7 mM). Then, these 5 high-MIC bacteria and 1 low-MIC bacterium, Bacillus sp. LB15 were inoculated onto sunflower grown in soil supplemented with 250 mg/kg of Cd. After 60 days, all inoculated plants accumulated significantly higher Cd concentration than the non-inoculated counterparts, and those inoculated with strain LB51 showed the highest Cd accumulation and growth. Interestingly, strain LB15 with low MIC also enhanced Cd accumulation in plants. The results suggest that these bacteria, particularly strain LB51, could be applied to improve Cd accumulation in plants, and that bacteria with low MIC also have the potential to enhance the efficiency of phytoextraction.     

Isolation and characterization of endophytic bacterium LRE07 from cadmium hyperaccumulator Solanum nigrum L. and its potential for remediation

Valuable endophytic strains facilitating plants growth and detoxification of heavy metals are required because the application of plant–endophyte symbiotic system is a promising potential technique to improve efficiency of phytoremediation. In this study, endophytic bacterium LRE07 was isolated from cadmium hyperaccumulator Solanum nigrum L. It was identified as Serratia sp. by 16S rRNA sequence analysis. The endophytic bacterium LRE07 was resistant to the toxic effects of heavy metals, solubilized mineral phosphate, and produced indoleacetic acid and siderophore. The heavy metal detoxification was studied in growing LRE07 cells. The strain bound over 65% of cadmium and 35% of zinc in its growing cells from single metal solutions 72 h after inoculation. Besides the high removal efficiencies in single-ion system, an analogous removal phenomenon was also observed in multi-ions system, indicating that the endophyte possesses specific and remarkable heavy metal remediation abilities.     

Increased plant growth and copper uptake of host and non-host plants by metal-resistant and plant growth-promoting endophytic bacteria

The effects of inoculation with two metal-resistant and plant growth-promoting endophytic bacteria (Burkholderia sp. GL12 and Bacillus megaterium JL35) were evaluated on the plant growth and Cu uptake in their host Elsholtzia splendens and non-host Brassica napus plants grown in natural Cu-contaminated soil. The two strains showed a high level of ACC deaminase activities. In pot experiments, inoculation with strain GL12 significantly increased root and above-ground tissue dry weights of both plants, consequently increasing the total Cu uptake of E. splendens and Brassica napus by 132% and 48.2% respectively. Inoculation with strain JL35 was found to significantly increase not only the biomass of B. napus, consequently increasing the total Cu uptake of B. napus by 31.3%, but Cu concentration of E. splendens for above-ground tissues by 318% and roots by 69.7%, consequently increasing the total Cu uptake of E. splendens by 223%. The two strains could colonize the rhizosphere soils and root interiors of both plants. Notably, strain JL35 could colonize the shoot tissues and significantly increase the translocation factors and bioaccumulation factors of E. splendens. These results suggested that Burkholderia sp. GL12 and B. megaterium JL35 were valuable bacterial resource which had the potential in improving the efficiency of Cu phytoextraction by E. splendens and B. napus in a natural Cu-contaminated soil.     

Phytoextraction capacity of trees growing on a metal contaminated soil

Phytoremediation is an innovative biological technique to reclaim land contaminated by heavy metals or organic pollutants. In the present work, we studied the ability of five woody species to extract heavy metal (copper, zinc or cadmium) from a polluted soil to their above-ground tissues. Metal content in leaves and twigs was determined. Salix and Betula transferred zinc and cadmium to leaves and twigs, but Alnus, Fraxinus and Sorbus excluded them from their above-ground tissues. None of the species considered transferred copper to the shoots.     

Inoculating wheat (Triticum aestivum L.) with the endophytic bacterium Serratia sp. PW7 to reduce pyrene contamination

This research was conducted to find an optimal inoculation way for a pyrene-degrading endophytic Serratia sp. PW7 to colonize wheat for reducing pyrene contamination. Three inoculation ways, which are soaking seeds in inocula (TS), dipping roots of seedlings in inocula (TR), and spraying inocula on leaves of seedlings (TL), were used in this study. Inoculated seedlings and noninoculated seedlings (CK) were, respectively, cultivated in Hoagland solutions supplemented with pyrene in a growth chamber. The results showed that strain PW7 successfully colonized the inoculated seedlings in high numbers, and significantly promoted the growth of seedlings (TS and TR). More importantly, strain PW7 reduced pyrene levels in the seedlings and the Hoagland solutions. Compared to the noninoculated seedlings, the pyrene contents of the inoculated seedlings were decreased by 35.7-86.3% in the shoots and by 26.8–60.1% in the roots after 8-day cultivation. By comparing the efficiencies of decreasing pyrene residues, it can be concluded that TR was an optimal inoculation way for endophytic strains to colonize the inoculated plants and to reduce the pyrene contamination. Our findings provide an optimized inoculation way to reduce organic contamination in crops by inoculating plants with functional endophytic bacteria.     

Cadmium and Nickel Toxicity for <Emphasis Type="Italic">Sinapis alba</Emphasis> Plants Inoculated with Endophytic Strains of <Emphasis Type="Italic">Bacillus subtilis</Emphasis>

We studied the effect of cadmium and nickel on Sinapis alba L. plants inoculated with endophytic strains of Bacillus subtilis. It was shown that treatment of S. alba seeds with endophytic strains of bacteria B. subtilis improves plant resistance to the toxic effect of cadmium and nickel and reduces manifestation of oxidative stress in the presence of higher levels of metal ions in the above-ground part of plants. Anti-stress effect and the ability of endophytic strains of B. subtilis to intensify uptake of cadmium and nickel ions by S. alba plants may be used for phytoextraction of heavy metals and stimulation of plant growth in contaminated areas.     

Response of ectomycorrhizalPinus banksiana andPicea glauca to heavy metals in soil

Pinus banksiana andPicea glauca inoculated or not with the ectomycorrhizal fungusSuillus luteus were grown in a sandy loam soil containing a range of Cd, Cu, Ni, Pb and Zn concentrations. Ectomycorrhizal colonization rates were significantly reduced on Pinus and Picea seedlings by the heavy metals, particularly Cd and Ni. Needle tissue metal concentrations were lower in ectomycorrhizal seedlings at low soil metal concentrations. However, at higher soil concentrations, heavy metal concentrations of needle tissue were similar in ectomycorrhizal and nonmycorrhizal plants. The growth of nonmycorrhizal seedlings exposed to heavy metals was reduced compared to those inoculated withSuillus luteus. Apparently ectomycorrhizal colonization can protect Pinus and Picea seedlings from heavy metal toxicity at low or intermediate soil concentrations of Cd, Cu, Ni, Pb and Zn.     

Isolation and characterization of heavy metals resistant bacteria from Lagos Lagoon

A total of 228 bacteria with an ability to resist toxic heavy metals were isolated from 8 selected sites of the Lagos Lagoon. The bacteria isolated wereStaphylocaccus sp.,Bacillus sp.,Pseudomonas sp.,Streptococcus sp.,Moraxella sp.,Escherichia coli, Proteus sp.,Klebsiella sp. andSalmonella sp. The heavy metals to which resistance was recorded were mercury, lead, zinc, cobalt, copper and chromium. The lagoon sites from which the highest number of resistant bacteria were isolated were Marina and Ebute-Ero. The heavy metal to which most bacteria were resistant was cobalt, while the least was chromium. The significance of the result is discussed in relation to the Nigerian environment and human health.     

Nitrate-dependent control of root architecture and N nutrition are altered by a plant growth-promoting Phyllobacterium sp

Both root architecture and plant N nutrition are altered by inoculation with the plant growth-promoting rhizobacteria (PGPR) Phyllobacterium strain STM196. It is known that NO₃⁻ and N metabolites can act as regulatory signals on root development and N transporters. In this study, we investigate the possible interrelated effects on root development and N transport. We show that the inhibition of Arabidopsis lateral root growth by high external NO₃⁻ is overridden by Phyllobacterium inoculation. However, the leaf NO₃⁻ pool remained unchanged in inoculated plants. By contrast, the Gln root pool was reduced in inoculated plants. Unexpectedly, NO₃⁻ influx and the expression levels of AtNRT1.1 and AtNRT2.1 genes coding for root NO₃⁻ transporters were also decreased after 8 days of Phyllobacterium inoculation. Although the mechanisms by which PGPR exert their positive effects remain unknown, our data show that they can optimize plant development independently from N supply, thus alleviating the regulatory mechanisms that operate in axenic conditions. In addition, we found that Phyllobacterium sp. elicited a very strong induction of AtNRT2.5 and AtNRT2.6, both genes preferentially expressed in the shoots whose functions are unknown.     

The effects of toxic metals,content of nutrients and inoculation with mycorrhizal fungi on the level of phenolics in roots and growth of Scots pine seedlings

The effects of two substrates and several strains of mycorrhizal fungi on the content of soluble phenolics in roots and growth of Scots pine seedlings was investigated. The first substrate was fertile and contaminated with copper, zinc and lead, whereas the second one displayed nutrient deficiency. The dry weights of needles, trunks, roots and the total biomass were higher in groups of seedlings inoculated with mycorrhizal fungi on fertile and polluted substrate. Inoculation of pine seedlings on this substrate resulted in a decrease in concentration of phenolics in roots and except for seedlings inoculated with Laccaria laccata negatively influenced the above-ground part: root ratio.     

一株耐盐甲基杆菌Methylobacterium sp.W-1的分离及促生潜能研究

[背景] 多种甲基杆菌属细菌对寄主植物有促生作用,其分布区域较广。筛选具有耐盐与促生特性的甲基杆菌属菌株可为微生物菌肥的开发提供依据。[目的] 从新疆乌尔禾地区盐渍土壤中筛选耐盐促生菌,对其培养基成分进行优化及促生能力进行研究,为微生物菌肥的开发提供依据。[方法] 采用阿须贝无氮培养基筛选耐盐菌株,对菌株进行基因序列分析及生理生化测定,采用平板试验法初步研究该菌对拟南芥的生长影响。[结果] 筛选出中度耐盐菌株W-1,经鉴定为甲基杆菌属（Methylobacteriumsp.）。菌株生长最佳无机盐为NaCl,最适浓度为1%–3%,最高耐受浓度达7%。最佳氮源为酸水解酪蛋白,产生长素最高达33.53 mg/L。溶磷能力达28.71 mg/L。菌株W-1接种拟南芥幼苗后叶绿素a和叶绿素b含量均高于对照组,同时对其根系发育有显著的促进作用。[结论] 菌株W-1促生性能显著,可为生物肥料制备提供菌种资源。     

Employment of Rhizobacteria for the Inoculation of Barley Plants Cultivated in Soil Contaminated with Lead and Cadmium

In laboratory experiments, the rhizobacteria Azospirillum lipoferum 137, Arthrobacter mysorens7, Agrobacterium radiobacter 10, and Flavobacterium sp. L30 were found to have a relatively high resistance to the toxic heavy metals lead and cadmium (except that strain L30 was found to be sensitive to Cd). When introduced by means of seed bacterization, the heavy metal–resistant strains actively colonized the rhizosphere of barley plants cultivated in uncontaminated and contaminated soils. In both pot and field experiments, seed bacterization improved the growth of barley plants and the uptake of nutrient elements from soil contaminated with Pb and Cd. The bacterization also prevented the accumulation of Pb and Cd in barley plants, thereby mitigating the toxic effect of these heavy metals on the plants.     

Biomethanation of Spent Wash: Bacterial Pretreatment to Remove Heavy Metals by Adsorption

In a semicontinuous fermentation system, biomethanation of diluted spent wash (DW, initial COD 25–27 g/l) resulted in only 0.2 l/l of methane production in 20 d. Two capsular Gram-negative strains of bacteria were used for adsorption of heavy metals such as lead, copper, and zinc from spent wash. Strain I removed 64 % of the lead in 1 h and 82% of the copper in 2 h, while strain II removed 76% of the zinc in 2 h. The diluted spent wash from which heavy metals were removed was supplemented with synthetic medium and an acidophilic strain of Candida sp. This treatment improved methanogenesis. In 12 d, 4.9 l/l of biogas containing 63% methane was produced.     

Intercellular colonization and growth promoting effects of Methylobacterium sp. with plant-growth regulators on rice (Oryza sativa L. Cv CO-43)

The Methylobacterium sp. strain NPFM-SB3, isolated from Sesbania rostrata stem nodules possessed nitrogenase activity and nodA genes. Pure culture of NPFM-SB3 strain produced indole-3-acetic acid, cytokinins and on inoculation to rice plants resulted in numerous lateral roots. Inoculation of synthetic auxins 2,4-dichlorophenoxy acetic acid, naphthalene acetic acid or flavonoids naringenin and dihydroxy-4-methoxyisoflavone individually or to bacterial inoculated rice seedlings improved the plant growth and lateral root formation under hydroponic condition. The formation of nodule-like structure and nitrogenase activity which is purely auxin dependent was observed in 2,4-dichlorophenoxy acetic acid treatments to Methylobacterium sp. NPFM-SB3 inoculated rice plants. The rhizobia entered through fissures formed due to lateral root emergence and spread intercellularly in the nodular structures concluded that the effect of 2,4-dichlorophenoxy acetic acid treatment for rice seedlings grown under gnotobiotic conditions is to create a niche in which these bacteria can grow.     

Survival in Sterile Soil and Atrazine Degradation of Pseudomonas sp. Strain ADP Immobilized on Zeolite

In laboratory settings, the ability of bacteria and fungi to degrade many environmental contaminants is well proven. However, the potential of microbial inoculants in soil remediation has not often been realized because catabolically competent strains rarely survive and proliferate in soil, and even if they do, they usually fail to express their desired catabolic potential. One method to address the survival problem is formulating the microorganisms with physical and chemical support systems. This study investigates the survival of Pseudomonas sp. strain ADP in sterile soil and its retention of atrazine-degrading functionality. Assessment was conducted with free and zeolite-immobilized bacteria incorporated into the soil. Pseudomonas sp. strain ADP remained viable for at least 10 weeks when stored at 15°C in sterile soil. Cell numbers increased for both free and zeolite-immobilized bacteria during this period, except for free cells when grown in Miller's Luria-Bertani medium, which exhibited constant cell numbers over the 10 weeks. Only the zeolite-immobilized cell retained full functionality to degrade atrazine after 10 weeks in sterile soil regardless of the medium used to culture Pseudomonas sp. strain ADP. Functionality was diminished in free-cell inoculations except when using an improved culture medium. Survival of zeolite-immobilized Pseudomonas sp. strain ADP separated from the soil matrix after 10 weeks’ incubation was significantly (p < .05) greater than in soil inoculated with free cells or in the soil fraction inoculated by release from zeolite-immobilized Pseudomonas sp. strain ADP.     

Isolation and characterization of heavy metal tolerant Gram-positive bacteria with bioremedial properties from municipal waste rich soil of Kestopur canal (Kolkata), West Bengal,India

The present study was conducted to determine the culturable bacterial profile from Kestopur canal (Kolkata, India) and analyze their heavy metal tolerance. In addition to daily sewage including solid and soluble wastes, a considerable load of toxic metals are released into this water body from industries, tanneries and agriculture, household as well as health sectors. Screening out microbes from such an environment was done keeping in mind their multifunctional application especially for bioremediation. Heavy metals are major environmental pollutants when present in high concentration in soil and show potential toxic effects on growth and development in plants and animals. Some edible herbs growing in the canal vicinity, and consumed by people, were found to harbour these heavy metals at sub-toxic levels. The bioconcentration factor of these plants being <1 indicates that they probably only absorb but not accumulate heavy metals. All the thirteen Grampositive bacteria isolated from these plants rhizosphere were found to tolerate high concentration of heavy metals like Co, Ni, Pb, Cr, Fe. Phylogenetic analysis of their 16S rDNA genes revealed that they belonged to one main taxonomic group — the Firmicutes. Seven of them were found to be novel with 92–95% sequence homology with known bacterial strains. Further microbiological analyses show that the alkaliphilic Bacillus weihenstephanensis strain IA1 and Exiguobacterium aestuarii strain CE1, with selective antibiotic sensitivity along with high Ni²⁺ and Cr⁶⁺ removal capabilities, respectively, can be prospective candidates for bioremediation.     

Phytoremediation of landfill leachate waste contaminants through floating bed technique using water hyacinth and water lettuce

Abstract

In the present study, the effectiveness of water hyacinth and water lettuce was tested for the phytoremediation of landfill leachate for the period of 15?days. Fifteen plastic containers were used in experimental setup where aquatic plants were fitted as a floating bed with the help of thermo-pole sheet. It was observed that both plants significantly (p?<?0.05/p?<?0.01/p?<?0.001) reduce the physicochemical parameters pH, TDS, BOD, COD and heavy metals like Zn, Pb, Fe, Cu and Ni from landfill leachate. Maximum reduction in these parameters was obtained at 50% and 75% landfill leachate treatment and their removal rate gradually increased from day 3 to day 15 of the experiment. The maximum removal rate for heavy metals such as for Zn (80–90%), Fe (83–87%) and Pb (76–84%) was attained by Eichhornia crassipes and Pistia stratiotes. Value of bioconcentration and translocation factor was less than 1 which indicates the low transport of heavy metals from roots to the above-ground parts of the plants. Both these plants accumulate heavy metals inside their body without showing much reduction in growth and showing tolerance to all the present metals. Therefore, results obtained from the study suggest that these aquatic plants are suitable candidate for the removal of pollution load from landfill leachate.     

Rhizostabilization of metals in soils using Lupinus luteus inoculated with the metal resistant rhizobacterium Serratia sp. MSMC541

The aim of this work was to test Lupinus luteus plants, inoculated with metal resistant rhizobacteria, in order to phytostabilise metals in contaminated soils. The resistance to heavy metals of strains isolated from nodules of Lupinus plants was evaluated. The strain MSMC541 showed multi-resistance to several metals (up to 13.3 mM As, 2.2 mM Cd, 2.3 mM Cu, 9 mM Pb and 30 mM Zn), and it was selected for further characterization. Furthermore, this strain was able to biosorb great amounts of metals in cell biomass. 16S rDNA sequencing positioned this strain within the genus Serratia. The presence of arsenic resistance genes was confirmed by southern blot and PCR amplification. A rhizoremediation pot experiment was conducted using Lupinus luteus grown on sand supplemented with heavy metals and inoculated with MSMC541. Plant growth parameters and metal accumulation were determined in inoculated vs. non-inoculated Lupinus luteus plants. The results showed that inoculation with MSMC541 improved the plant tolerance to metals. At the same time, metal translocation to the shoot was significantly reduced upon inoculation. These results suggest that Lupinus luteus plants, inoculated with the metal resistant strain Serratia sp. MSMC541, have a great potential for phytostabilization of metal contaminated soils.     

砂生槐根瘤内生菌对青稞种子萌发及幼苗的促生作用

该文以接种不同砂生槐根瘤内生菌的黑青稞种子和不接种菌株的黑青稞种子为研究材料,采用培养皿作为基质,观察黑青稞种子萌发及幼苗生长情况,测定接种不同根瘤内生菌后的黑青稞发芽率、发芽势、发芽指数、株高、根长、须根数、根冠比、植株全株干/鲜重的生理性状,并对各不同处理进行隶属函数综合评价.结果表明:菌株R7和R17的发芽率均达...