COLONIZATION OF VIGNA RADIATA ROOTS BY CHROMIUM RESISTANT BACTERIAL STRAINS OF OCHROBACTRUM INTERMEDIUM, BACILLUS CEREUS AND BREVIBA CTERIUM SP.

The rhizosphere is the constricted zone of soil surrounding theroot that is under the immediate influence of root system.This zoneis rich in nutrients compared with bulk soil,due to the accumula-tion of various organic compounds released from roots by exu…     

Identification of Bacillus methylotrophicus and its application in preventing fly maggot production in the environment北大核心CSCD

This research aimed to screen Bacillus spp. to prevent the production of fly maggot on kitchen wastes from soil in the experimental bases of the South China Agricultural University. A nutrient-rich medium was used to isolate the Bacillus spp. with high temperature treatment. The seventeen Bacillus strains were obtained and assigned to three groups by using Insertion Sequence based PCR (IS-PCR) DNA fingerprinting patterns. The homology of the 16S rDNA gene was 100% between Group I and Bacillus methylotrophicus CBMB 205T, 99.61% between Group II and Bacillus aerophilus 28KT, and 99.87% between Group III and Bacillus cereus ATCC 14579T. The results of kitchen waste tests proved that the representative bacteria of Group I RF2 had the ability to prevent fly maggot production on kitchen wastes. Furthermore, the results of physiological and biochemical tests, carbon utilization tests, and antagonists against plant pathogen tests showed that the bacteria from Group I RF2 had the ability to decompose glucose into pyruvate and then decarboxylate pyruvate to diacetyl under alkaline conditions, convert ammonia to intracellular amino acids or other kinds of nitrogenous compounds, use many kinds of carbon source for self-growth, and be antagonistic against plant pathogenic rice sheath blight disease, banana fusarium wilt, and Fusarium oxysporum. Besides, the bacteria from RF2 could secret organic acids to dissolve insoluble phosphate [Ca3(PO4)2] for its own growth by decreasing the pH. Group I RF2 was a strong plant-promotion bacterium, and had good prospects of application for preventing fly maggot production on kitchen wastes. © 2018 Science Press. All rights reserved.     

Role of phosphate solubilizing bacteria on rock phosphate solubility and growth of aerobic rice

Use of phosphate-solubilizing bacteria (PSB) as inoculants has concurrently increased phosphorous uptake in plants and improved yields in several crop species. The ability of PSB to improve growth of aerobic rice (Oryza sativa L.) through enhanced phosphorus (P) uptake from Christmas island rock phosphate (RP) was studied in glasshouse experiments. Two isolated PSB strains; Bacillus spp. PSB9 and PSB16, were evaluated with RP treatments at 0, 30 and 60 kg ha(-1). Surface sterilized seeds of aerobic rice were planted in plastic pots containing 3 kg soil and the effect of treatments incorporated at planting were observed over 60 days of growth. The isolated PSB strains (PSB9 and PSB16) solubilized significantly high amounts of P (20.05-24.08 mg kg(-1)) compared to non-inoculated (19-23.10 mg kg(-1)) treatments. Significantly higher P solubilization (24.08 mg kg(-1)) and plant P uptake (5.31 mg plant(-1)) was observed with the PSB16 strain at the highest P level of 60 kg ha(-1). The higher amounts of soluble P in the soil solution increased P uptake in plants and resulted in higher plant biomass (21.48 g plant(-1)). PSB strains also increased plant height (80 cm) and improved root morphology in aerobic rice. The results showed that inoculation of aerobic rice with PSB improved phosphate solubilizing activity of incorporated RP.     

Characterisation of growth and biochemical response of Onopordum acanthium L. under lead stress as affected by microbial inoculation

Microbial associations may influence the negative effects of potentially toxic elements on plants. In a greenhouse experiment, the growth; biochemical response; and Pb, Fe, and Zn uptake of Onopordum acanthium L. were investigated in response to inoculation with arbuscular mycorrhizal fungi, AMF (a mixture of Funneliformis mosseae, Rhizophagus irregularis, and Rhizophagus fasciculatus) and plant growth-promoting rhizobacteria, PGPR (a mixture of Pseudomonas species including P. putida, P. fluorescens, and P. aeruginosa) at increased Pb levels in soil. The treatments were arranged as a factorial experiment based on a randomised complete block design. Results revealed that inoculation with AMF and PGPR decreased Pb toxicity in plants. Inoculated plants with AMF and PGPR had higher shoot and root dry weight compared with the non-inoculated plants. In this study, AMF and PGPR inoculation led to a significant increase (P?≤?.05) in chlorophyll a, b, chlorophyll a+b, carotenoid, proline, and relative water content of plants. Furthermore, AMF and PGPR inoculation likely played a more important role in growth and Pb uptake in O. acanthium L. Our results suggest that AMF and Pseudomonas bacteria could be effective bio-inoculants for enhancing the plant growth and Pb uptake by inhibiting the adverse effects of Pb in O. acanthium.     

Effects of two different intercropping systems on arbuscular mycorrhizal fungal colonization and polychlorinated biphenyl (PCB) dissipation北大核心CSCD

Polychlorinated biphenyls (PCBs) are typical organic contaminants in the environment. It is indicated that plants and soil microorganisms have a positive synergistic effect on the remediation of PCB-contaminated soil. To investigate the effect of intercropping on arbuscular mycorrhizal (AM) fungal colonization and PCB remediation, a pot-cultivation experiment with two intercropping treatments, corn (Zea mays L.) / ryegrass (Lolium perenne L.) and corn/alfalfa (Medicago sativa L.), and a corn monoculture was conducted in a greenhouse. All treatments were inoculated with Funneliformis mosseae M47V. Plant biomass, root mycorrhizal colonization rate, concentration of PCBs and their homologs in soil, 16S rDNA gene abundance, and community composition measured by Terminal Restriction Fragment Length Polymorphism (T-RFLP) were determined after harvesting the plants. Intercropping significantly increased the root mycorrhizal colonization rate and plant biomass of corn (P < 0.05), as well as the available N content of the soil. A significant difference of the bacterial community composition was found among different treatments (P < 0.05). Compared with corn monoculture, corn/alfalfa intercropping significantly increased soil bacteria abundance (P < 0.05). The dissipation rates of total PCBs, as well as that of penta-chloro biphenyls were significantly increased in the intercropping treatments, when compared to the corn monoculture treatment. Moreover, corn/ryegrass intercropping has a significantly positive effect on the dissipation of tri-chloro biphenyls. Non-metric multidimensional scaling (NMDS) analysis indicated that the PCBs homologues composition were significantly correlated with the relative abundance of 128 bp and 148 bp T-RFs. Corn intercropping with ryegrass or alfalfa has a positive effect on root mycorrhizal colonization rate and plant biomass of corn. Inoculation of AM fungi in intercropping treatments significantly improved the efficiency of PCB remediation by promoting bacterial abundance and shifting the bacterial community composition. In conclusion, intercropping combined with AM fungi have positive synergistic effects on the remediation of PCB-contaminated soils. © 2018 Science Press. All rights reserved.     

芽胞杆菌属(Bacillus sp.)10株细菌混合制剂对4种作物出苗及苗期生长的影响

以10株具有促生及抑制病害的芽胞杆菌属菌株(Bacillus sp．)的培养物，按不同比例配制成5个混合剂型细菌制剂．A、B、C、D剂型播种时接种不结球小白菜30d后，株高、叶片数、根长和干重分别增加7．8％、6．2％、9．4％和13．8％，除C处理的株高与对照差异不显著外，其余均达显著水平．接种A和B剂型显著提高豌豆出苗率，出苗9d时两菌剂处理的地上和地下部干重分别平均提高92．3％和183．3％，并发现5株供试菌株对引起豌豆病害病原菌有明显的抑菌作用．以A、B、E三个剂型菌悬液培养水稻种子4d时，各处理的平均芽长提高33．3％，根长提高16．0％，培养25d时株高、根数和地上部干重平均分别提高16．0％、9．5％和22．7％，均达显著水平．B剂型的培养物培养小麦27d时发现对株高、叶片数和植株干重的影响都不显著，但对根数和根重有显著的促进作用．综合分析认为，A菌剂最有利于供试作物出苗和苗期生长，其次为B剂型．表5参17     

油菜根系分泌物对不同作物幼苗生长的化感效应

在实验室采用发芽试验的方法研究了油菜Brassicacampestris根系分泌物对小麦、油菜、蚕豆和玉米种子活力、幼苗生长发育及生理生化特性造成的化感效应。结果表明,油菜根系分泌物的化感累加作用对不同作物种子发芽率、幼苗芽长、芽质量、根长、根质量、根系活力以及幼芽过氧化物酶(POD)活性和丙二醛(MDA)含量均具有显著影响,其化感效应对小麦的影响程度最弱,其中对小麦的种子发芽率、幼苗根长、芽干物质量、POD活性和根系活力以及各作物幼芽细胞膜的毒害程度均表现出促进作用,而对小麦幼苗其它生长特性以及油菜、蚕豆和玉米幼苗的所有生长特性均表现为抑制作用,表明油菜根系分泌物对不同作物及不同生长特性的化感效应具有不同的选择性。因此,合理搭配油菜作物的间、套、轮作是其夺取优质、高产栽培的关键技术。     

Effects of exotic Spartina alterniflora on rhizosphere and endophytic bacterial community structures and diversity in roots of native mangroves北大核心CSCD

Root-associated microbial communities are very important for biogeochemical cycles of carbon, nitrogen, and sulfur in wetland ecosystems, and help to enhance the mechanisms of plant invasions. In the estuary of Jiulong River (China), Spartina alternifiora has widely invaded Kandelia obovata-dominated habitats, making it necessary to investigate the influence of rootassociated bacteria. The endophytic and rhizosphere bacterial community structures associated with selected plant species were investigated using the barcoded Illumina paired-end sequencing technique. The diversity indices of bacteria associated with the roots of S. alterniflora were higher than those of the transition stands and K. obovata monoculture. Using principal coordinate analysis with UniFrac metrics, the comparison of diversity showed that all samples could be significantly clustered into three major groups, according to the bacterial communities of origin. Four phyla, namely, Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes, were abundant in the rhizoplane of the two salt marsh plants, whereas Cyanobacteria and Proteobacteria were the more abundant endophytic bacteria. Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes in the rhizosphere bacteria of S. alterniflora accounted for 78.0%, 5.6%, 3.3%, and 1.6%, respectively. Members of the phyla Spirochaetes and Chloroflexi were found among the endophytic bacteria of S. alterniflora and K. obovata, respectively. Using linear discriminate analysis, we found some dominant rhizoplane and endophytic bacteria, including Pseudoalteromonadaceae, Vibrionaceae, Methylophilaceae, and Desulfovibrio, which could potentially affect the carbon, nitrogen, and sulfur cycles. Of interest was that endophytic bacteria were more sensitive to plant invasion than rhizosphere bacteria. Thus, the results provide evidence for the isolation of functional bacteria and the effects of root-associated microbial groups on S. alterniflora invasions. © 2018 Science Press. All rights reserved.     

石灰对重金属铅影响玉米生长的抑制效应研究

采用盆栽试验,研究了在施用石灰改良的条件下,土壤重金属铅污染对玉米生长的影响。结果表明:土壤重金属铅污染质量分数越高,玉米吸收重金属铅越多,对玉米的生长影响越大。石灰对重金属铅影响玉米生长的抑制效应表现在株高、叶面积、根容积等,改良处理与单一铅污染的处理差异显著。玉米的不同部位对重金属铅吸收由多到少的顺序为根→茎、叶→籽实。     

Antagonistic potential of fluorescent pseudomonads and control of charcoal rot of chickpea caused by Macrophomina phaseolina

The effectiveness of plant growth promoting rhizobacteria especially Pseudomonas fluorescens isolates were tested against charcoal rot of chickpea both in green house as well as in field conditions. Most of the isolates reduced charcoal rot disease and promoted plant growth in green house. A marked increase in shoot and root length was observed in P. fluorescens treated plants. Among all the P. fluorescens isolates Pf4-99, was found most effective in the improvement of chickpea crop in green house as well as in field. Pf4-99 effectively promoted plant growth and produced indole acetic acid in culture medium. This isolate also inhibited the mycelial growth of the M. phaseolina under in vitro conditions and reduced the disease severity Potential isolate (Pf4-99) also significantly increased the biomass of the chickpea plants, shoot length, root length and protein content of the chickpea seeds. A part from these, the total number of seeds per plant and their weight were also enhanced. The colonization of Pf4-99 reduced the incidence of seed mycoflora by which indirectly enhanced the seed germination and vigour index of seedlings. The observations revealed that isolate Pf4-99 is quite effective to reduce the charcoal rot disease both in field and greenhouse, and also increases seed yields significantly Therefore, this isolate appears to be an efficient biocontrol agent against charcoal rot disease as well as yield increasing rhizobacterium.     

Growth of Brassica juncea under chromium stress: influence of siderophores and indole 3 acetic acid producing rhizosphere bacteria

Plant growth promoting rhizobacterial (PGPR) strains A3 and S32 have been shown to promote the growth of Brassica juncea under chromium stress which has been related to the microbial production of siderophores and indole 3 acetic acid (IAA). The aim of the present study is to evaluate the importance of siderophores and IAA producing PGPR on the growth of Brassica juncea under chromium stress. The production of IAA and siderophores were observed in the strains A3 and S32, respectively. Both PGPR strains promote the growth of Brassica juncea under chromium stress. The maximum growth was observed in plants inoculated with siderophores producing strain 32. Both the bacterial inoculum did not influence the uptake of chromium by plants. The present observation showed that PGPR isolates A3 and S32 are capable of protecting the plants against the inhibitory effects of chromium by producing the siderophores and IAA.     

培养条件对产酸克雷伯氏菌SG-11生物合成IAA影响的研究

研究了产酸克雷伯氏菌（Ｋｌｅｂｉｓｅｌｌａ ｏｘｙｔｏｃａ）ＳＧ－１１菌株的培养条件对其ＩＡＡ生物合成的影响。结果表明：该菌生长到稳定期时才开始大量产生ＩＡＡ；在基本培养基中，该菌对不同氮源的利用有别，在以（ＮＨ４）２ＳＯ４为氮源时，ＩＡＡ的产量最高，作为碳源的葡萄糖当加入浓度为６ｇ／Ｌ时，游离态ＩＡＡ的产量最高；在ＬＢ培养基中，当ｐ（Ｏ２）由正常值降低１／４时，ＩＡＡ的产生量陡然下降，灭菌前，把     

荧光假单胞菌群根部定殖的研究进展

本文从定殖动态、引入菌株的特性及其环境条件的影响等方面综述了近１０ａ来有关荧光假单胞菌群根部定殖的研究进展．     

Bacterial colonization of the phyllosphere of nineteen plant species and antimicrobial activity of their leaf secondary metabolites against leaf associated bacteria

Summary. The scope of this work was to examine whether leaf constitutive secondary metabolites play a role in determining bacterial colonization of the phyllosphere. To this aim, we surveyed nineteen native or cultivated plant species that share a common bacterial pool in a North Mediterranean area, and estimated the size of total and ice nucleation active (INA) bacterial populations on their leaves. Large differences in the colonization of their phyllosphere were found; the population size of epiphytic bacteria ranged from 7.5 × 10² to 1 × 10⁶ CFU/g fresh weight, in eucalypt and celery, respectively. Species native in Mediterranean-type climate areas, particularly those belonging to the group of aromatic plants, are characterized by scarce presence of INA bacteria. The antibacterial activity of essential oils, surface phenolics and leaf tissue extracts was also estimated against the INA strains P. syringae and E. herbicola, isolated from two of these plant species. E. herbicola proved more sensitive than P. syringae. Of the species examined, oregano [Origanum vulgare L. subsp. hirtum (Link.) Ietswaart], an aromatic plant, had the highest antimicrobial activity, whereas six species showed no activity at all. Further experiments were performed with oregano and bean (Phaseolus vulgaris L.) that represent two extremes in their secondary metabolite content. Both plants were inoculated with P. syringae. By the end of incubation, the bacterial population on bean plants was about 100 times higher than that on oregano leaves. Scanning electron micrographs showed that bacterial growth on oregano leaves was confined to sites away from glandular hairs. Results from the bacterial colonization survey together with those from the toxicity tests showed that all species rich in antibacterial secondary metabolites harbored low leaf bacterial populations. These results provide substantial evidence that leaf secondary metabolites function as constitutive defense chemicals against microbial invasions. However, the fact that species with non- or moderately active leaf secondary metabolites are not always highly colonized suggests mediation of other unknown factors, the contribution of which requires further investigation.     

Alleviation of nickel stress by halophilic bacteria in mungbean(Vigna radiata)

Mungbean is an important, short-duration legume crop with high nutritive value for poor families, where protein and micronutrient scarcity are most pervasive. In developing countries, like Pakistan, where mungbean is one of the greatest sources of protein for underprivileged people, salinity and metal stresses are drastically limiting its yield. Therefore, it is necessary to explore the ways for promoting the growth of mungbean under stressed conditions. This study provides the basis for the use of two previously isolated halophilic and nickel-resistant bacteria [Bacillus subtilis and Halomonas aquamarina(1)] in promoting the growth of mungbean plant under nickel-stressed environments. These bacterial strains were previously found to improve the growth of plants under salinity because of their good biofilm-forming abilities. We hypothesized that these two halophilic and nickel-resistant biofilm-forming bacteria can help the plants to grow under nickel-stressed environments by promoting soil aggregation as they were previously reported to resist salinity and nickel stress, as well as were found to promote plant growth under saline environments. The results revealed that under nickel stress, both bacteria promote plant growth by facilitating the formation of soil aggregates through an increase in their extra polymeric substance(EPS) production.     

Diversity of root associated microorganisms of selected medicinal plants and influence of rhizomicroorganisms on the antimicrobial property of Coriandrum sativum

The total heterotrophic bacteria, actinomycetes and fungus were enumerated from the rhizosphere and non-rhizosphere soil of 50 selected locally available medicinal plants in and around Bharathiar University. In all the plants, population of microorganism were higher in the rhizosphere soil than in the non rhizosphere soil. Among the microorganisms, bacterial population was higher in number followed by fungus and actinomycetes. Of the medicinal plants, the maximum rhizosphere effect was observed in Annona squamosa and the minimum effect was seen in Eclipta alba and Cassia auriculata. Among the bacteria the dominant species was Bacillus followed by Pseudomonas, Enterobacter, Corynebacterium, Micrococcus and Serratia. The Streptomyces species was found to be dominant followed by Deuteromycetes and Frankia among the actinomycetes. Among the fungal isolates Rhizopus was found to be higher in number followed by Aspergillus, Penicillium, Mucor and Fusarium. About 70.96% of the bacterial isolates were found to be nitrate reducers and 90.60% of the bacteria solubilised phosphate. The rhizosphere bacterial isolates were also capable of hydrolyzing starch, cellulose, casein, urea and gelatin. The isolates of bacteria, actinomycetes and fungus were also able to produce phytohormone Indole-3-acetic acid (IAA). The maximum IAA production was recorded by Fusarium sp (5.8 mg/l). The rhizosphere bacterial isolates showed resistance to 14 commercially used antibiotics. In an attempt to check the influence of these plant growth promoting microorganisms on the antimicrobial property of Coriandrum sativum against Escherichia coli MTCC-443 and Aeromonas hydrophila MTCC-646, the results observed was not encouraging since the inoculants did not influence the antibacterial property. However extensive and in depth study is required to find out the influence of rhizomicroorganisms on the antibacterial property of medicinal plants. The other results clearly indicated that the rhizosphere microorganisms could be exploited for its innumerable properties and active metabolites.     

Alleviation of nickel stress by halophilic bacteria in mungbean (Vigna radiata)北大核心CSCD

Mungbean is an important, short-duration legume crop with high nutritive value for poor families, where protein and micronutrient scarcity are most pervasive. In developing countries, like Pakistan, where mungbean is one of the greatest sources of protein for underprivileged people, salinity and metal stresses are drastically limiting its yield. Therefore, it is necessary to explore the ways for promoting the growth of mungbean under stressed conditions. This study provides the basis for the use of two previously isolated halophilic and nickel-resistant bacteria [Bacillus subtilis and Halomonas aquamarina (1)] in promoting the growth of mungbean plant under nickel-stressed environments. These bacterial strains were previously found to improve the growth of plants under salinity because of their good biofilm-forming abilities. We hypothesized that these two halophilic and nickel-resistant biofilm-forming bacteria can help the plants to grow under nickel-stressed environments by promoting soil aggregation as they were previously reported to resist salinity and nickel stress, as well as were found to promote plant growth under saline environments. The results revealed that under nickel stress, both bacteria promote plant growth by facilitating the formation of soil aggregates through an increase in their extra polymeric substance (EPS) production. © 2018 Science Press. All rights reserved.     

镉在北京褐潮土中对玉米幼苗及其根际微生物的毒性效应

通过温室盆栽实验,研究了镉在北京褐潮土中对玉米(品种郑单958)幼苗的毒性效应及其生物富集特性,并通过聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)技术,探讨了镉对玉米根际微生物群落结构的影响。结果表明,高浓度(>100mg·kg-1)镉对玉米幼苗的生长发育有明显的抑制作用,北京褐潮土中镉引起玉米幼苗株高下降1/2的效应浓度(EC50)为654.6mg·kg-1,引起玉米根部和地上部干质量下降1/2的EC50分别为323.6和110.2mg·kg-1,玉米幼苗地上部生物量(干质量)可作为评价重金属生态毒性的适宜终点。玉米幼苗对镉有一定的吸收累积效应,镉在玉米幼苗各组织中的浓度分布为根>茎>叶,其中根部对镉有一定的富集作用(生物富集系数BAF>1)。镉污染可引起玉米根际微生物群落结构发生改变,高浓度(1000mg·kg-1)镉可导致部分微生物种群数量减少甚至完全消失,表明镉污染可对植物幼苗、植物根际微生物以及植物-微生物之间的相互作用造成重要的干扰和威胁。     

促进植物生长根圈细菌(PGPR)的研究现状

有机农业提倡与自然共存不破坏平衡,而自然界的土壤中存在许多可促进植物生长的植物根圈微生物(plant growth promoting rhizobacteria,PGPR),此类微生物可分泌促进植物生长的物质,并可诱导植物产生抗性基因,增强植物抗病.PGPR可产生有机物质促进植物生长,改善土壤肥力,增加可溶性磷及铁,诱发植物抗病、克服逆境、增强营养吸收,固氮或防治病害等,在有机农业上有助于植物增产,改善农业对化学肥料的依赖,生产出健康的作物.参25.     

The influence of introducing soft-shelled turtle on soil nitrogen-fixing microorganisms in paddy field北大核心CSCD

Soil microorganisms are an important part of the soil ecosystem, but studies on the structure of the soil bacterial community, especially the related genes, is lacking. This study aimed to investigate the structure of soil microorganisms and the connection between the soil microorganisms and different farming systems. We used the Illumina Genome Analyzer IIx to compare root soil bacteria (nifH gene) diversity characteristics between the rice-turtle co-culture system (R-T) and rice monoculture system (R-M), aiming to reveal the structural characteristics of soil microorganisms, and the connection between the soil microorganisms and different farming systems. The results of High Throughput Sequencing of nitrogen-fixing bacteria showed that the main nitrogen-fixing bacteria were classified as Bradyrhizobium, Geobacter, Anaeromyxobacter, Desulfovibrio, Sideroxydans, Desulfuromonas, Halorhodospira, Azotobacter, Desulfobulbus, Methylomonas, Pseudacidovorax, and Azospirillum. The diversity index of nitrogen-fixing bacteria in the root soil of R-T was higher than that of R-M, which was 6.85-0.07. The difference of soil nitrogen-fixation bacteria in the root soil of rice paddy was 23.86% among the different farming systems, and the difference in the different rice growth period was 16.97%. In summary, the rice growth period and different farming systems both have an influence on the nitrogen-fixation bacteria in paddy soil; the influence of the growth period on the nitrogen-fixation bacteria in the paddy soil was greater. © 2018 Science Press. All rights reserved.