Enhancement of Green Gram Nodulation and Growth by Bacillus Species

Rhizobacteria belonging to Bacillus sp. were isolated from the rhizosphere of green gram (Vigna radiata). Seed inoculation with the rhizobacteria showed stunting effect on root growth whereas four Bacillus strains caused stimulation of shoot growth at both 4 and 7 d of observations. Coinoculation of some Bacillus strains with effective Bradyrhizobium strain S24 resulted in enhanced nodulation and plant growth of green gram. The shoot dry mass (ratio to uninoculated control) varied from 1.32 to 6.33 at day 30 and from 1.28 to 3.55 at day 40 of plant growth. Nodule promoting effect after 40 d of plant growth was observed with majority of Bacillus strains except for MRS9 and MRS26. Maximum gains in nodulation, nitrogenase activity and plant growth were observed with Bacillus strains MRS12, MRS18, MRS22 and MRS27 after 40 d of plant growth, suggesting the usefulness of introduced rhizobacteria in improving crop productivity.     

Plant growth-promoting rhizobacteria modulate root-system architecture in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> through volatile organic compound emission

Extensive communication occurs between plants and microorganisms during different stages of plant development in which signaling molecules from the two partners play an important role. Volatile organic compounds (VOCs) emission by certain plant-growth promoting rhizobacteria (PGPR) has been found to be involved in plant growth. However, little is known about the role of bacterial VOCs in plant developmental processes. In this work, we investigated the effects of inoculation with twelve bacterial strains isolated from the rhizosphere of lemon plants (Citrus aurantifolia) on growth and development of Arabidopsis thaliana seedlings. Several bacterial strains showed a plant growth promoting effect stimulating biomass production, which was related to differential modulation of root-system architecture. The isolates L263, L266, and L272a stimulated primary root growth and lateral root development, while L254, L265a and L265b did not significantly alter primary root growth but strongly promoted lateral root formation. VOC emission analysis by SPME-GC-MS identified aldehydes, ketones and alcohols as the most abundant compounds common to most rhizobacteria. Other VOCs, including 1-octen-3-ol and butyrolactone were strain specific. Characterization of L254, L266 and L272a bacterial isolates by 16S rDNA analysis revealed the identity of these strains as Bacillus cereus, Bacillus simplex and Bacillus sp, respectively. Taken together, our data suggest that rhizospheric bacterial strains can modulate both plant growth promotion and root-system architecture by differential VOC emission.     

一株连香树根际促生细菌LWK2的分离鉴定及其全基因组序列分析

【背景】植物根际促生细菌是一类位于植物根际并能对植物生长产生促进作用的有益菌,在微生物肥料领域具有重要的应用价值。【目的】对濒危植物连香树根际的植物根际促生细菌进行分离筛选和连香树接种效应评价,挑选对连香树生长促进作用最为显著的菌种进行促生特性分析、菌种鉴定及全基因组序列测定与促生相关基因分析。【方法】利用相应筛选培养基对连香树根际土壤中解有机磷、溶无机磷和解钾细菌进行分离筛选,通过根际接种验证各菌株对连香树实生苗的促生能力。从中选取促生作用最为显著的细菌,进行解钾能力、产吲哚乙酸(indole-3-acetic acid,IAA)和1-氨基环丙烷-1-羧酸(1-aminocyclopropane-1-carboxylate,ACC)脱氨酶能力测定。利用菌体形态观察、16S rRNA基因序列分析及全基因组序列的平均核苷酸一致性比对进行菌种鉴定。最后利用基因组功能注释和比较基因组学分析对该菌株中的植物促生及重金属抗性相关基因进行解析。【结果】从连香树根际土壤中共筛选得到3株解有机磷细菌、2株溶无机磷细菌和2株解钾细菌,其中解钾细菌LWK2对连香树实生苗的生长促进作用最为显著。该菌株能够产...     

缓解花生连作障碍的根际促生菌分离及功能鉴定

【目的】长期连作障碍严重降低花生生产的产量及品质,根际促生菌可有效降解土壤中自毒化感物质、抑制植物病原菌生长及促进植物生长,从而有效缓解连作障碍问题。筛选优化具有缓解花生连作障碍能力的多功能根际益生微生物,验证其益生作用能力,为根际促生菌株在连作障碍中的应用提供理论依据及技术支持。【方法】采集连作12年地块花生根际土壤,利用以酚酸为唯一碳源的筛选培养基获得具有酚酸自毒化感物质降解及利用能力的根际促生菌,通过16S rRNA基因测序进行系统发育分析,确定根际促生菌菌株的分类地位,并验证其对植物病原菌生长抑制能力及解磷、解钾、产植物激素吲哚乙酸能力。【结果】从连作12年的花生发病土壤中获得7株可高效降解酚酸类自毒物质且降解底物多样的根际微生物菌株,经16S rRNA测序比对分别为克雷伯氏菌B02 (Klebsiella sp. B02)、克雷伯氏菌B07(Klebsiella sp. B07)、克雷伯氏菌B15 (Klebsiella sp. B15)、芽孢杆菌B28 (Bacillus sp. B28)、不动杆菌P09(Acinetobacter sp. P09)、布鲁氏杆菌VA05 (...     

<Emphasis Type="Italic">Bacillus megaterium</Emphasis> strain XTBG34 promotes plant growth by producing 2-pentylfuran

Several chemical changes in soil are associated with plant growth-promoting rhizobacteria. An endosporeforming bacterium, strain XTBG34, was isolated from a Xishuangbanna Tropical Botanical Garden soil sample and identified as Bacillus megaterium. The strain’s volatiles had remarkable plant growth promotion activity in Arabidopsis thaliana plants; after 15 days treatment, the fresh weight of plants inoculated with XTBG34 was almost 2-fold compared with those inoculated with DH5α. Head space volatile compounds produced by XTBG34, trapped with headspace solid phase microextraction and identified by gas chromatography-mass spectrometry, included aldehydes, alkanes, ketones and aroma components. Of the 11 compounds assayed for plant growth promotion activity in divided Petri plates, only 2-pentylfuran increased plant growth. We have therefore identified a new plant growth promotion volatile of B. megaterium XTBG34, which deserves further study in the mechanisms of interaction between plant growth-promoting rhizobacteria and plants.     

Tropane alkaloid production inDatura stramonium root cultures

Summary Tropane alkaloid production was studied in different root cultures ofDatura stramonium. Cultured roots were obtained with 10⁻⁶ M of indolbutyric acid. Their doubling times were from 6 to 19 days. Hyoscyamine content varied from 0.17 to 0.62% dry weight, and scopolamine content from 0.08 to 0.33% dry weight, depending on the lines. A comparison of the bioproductivity of these compounds in the pot-grown plant roots showed that it was two to three orders lower than cultured roots, and it increased one order of magnitude considering the productivity on the whole plant. Bioproductivity, growth capacity and alkaloid production stability during subsequent transfers (more than 2 yr) are reported. Only one root line (N5) showed excretion of the alkaloids to the culture medium. Characterization of three selected lines (N1, N5, and N9) showed that the highest alkaloid production is reached at the stationary phase of growth, with the exception of line N9.     

Plant-growth-promoting traits and antifungal potential of the Bacillus amyloliquefaciens YL-25

Biological control of plant soil-borne diseases has been shown as an attractive and an environment friendly alternative to chemical fungicides. Different microbial strains have been reported effective in controlling plant pathogens. Among those, Bacillus strains have their own importance. Bacillus amyloliquefaciens strain YL-25, isolated from the rhizosphere of healthy banana plant, was evaluated as bio-organic fertiliser (BIO) for its ability to promote plant growth and suppress Fusarium wilt of banana in pot experiment. The results showed that the application of the BIO containing strain YL-25 significantly promoted the growth of banana plants and decreased the incidence of Fusarium wilt compared to the organic fertiliser and chemical fertiliser (CF). In order to explore the beneficial mechanisms of strain YL-25, experiments were conducted in vitro. The phytohormones including indole-3-acetic acid and gibberellin A3 and stable antifungal compounds three homologous of iturin A were identified in the culture broth of strain YL-25. The strain YL-25 also showed the ability to degrade extracellular phytate in plate experiment. Owing to its innate multiple functional traits and biocontrol activity, the strain YL-25 may be used as plant-growth-promoting rhizobacterium and biocontrol agent against Fusarium wilt of banana.     

Enantiomeric differentiation of atropine/hyoscyamine by 13C NMR spectroscopy and its application to Datura stramonium extract

Introduction – The two enantiomers of hyoscyamine, an alkaloid found in many plant species, have distinct pharmacological and biological properties. Methods for the discrimination of both enantiomers are almost exclusively based on chiral HPLC/UV. Determination of the enantiomeric ratio (e.r.) of hyoscyamine is a challenging problem since this compound tends to racaemise, forming atropine during acid–base extraction. Objective – To develop a protocol for the calculation of enantiomeric ratio of hyoscyamine in a plant extract using a ¹³C NMR method. Methodology – Samples were prepared by extraction of dried Datura stramonium seeds. Observation of C12 and C15 NMR signals of hyoscyamine in the presence of one equivalent of TFA and sub‐stoichiometric amount of Yb(hfc)₃ allowed the calculation of the e.r. of S‐(?) and R‐(+)‐hyoscyamine. Results – The method was optimised with various mixtures of (+) and (?)‐hyoscyamine ranging from 50:50 (racaemic mixture, i.e. atropine) to 98.5:1.5. The e.r. measured by NMR on the signals of aromatic C12 and C15 were in agreement with the gravimetrically prepared samples. The method was then applied to an extract of Datura stramonium and S‐(?)‐hyoscyamine was the unique enantiomer. Conclusion – The study showed that the e.r. determination of atropine/hyoscyamine was achieved with a routine NMR spectrometer, using CLSR/TFA on pure compounds as well as on the crude extract of Datura stramonium. Copyright © 2010 John Wiley & Sons, Ltd.     

Improvement in symbiotic efficiency of chickpea (Cicer arietinum) by coinoculation of Bacillus strains with Mesorhizobium sp. Cicer

Rhizobacteria belonging to Bacillus sp. were isolated from the rhizosphere of chickpea (Cicer arietinum). Ten Bacillus strains were studied for their antifungal activity, effect on seedling emergence and plant growth promotion. Two Bacillus strains CBS127 and CBS155 inhibited the growth of all the four pathogenic fungi tested on nutrient agar medium plates in vitro. Seed inoculation with different Bacillus strains showed stimulatory effect on root and shoot growth at 10 d of observation in comparison to control whereas four Bacillus strains CBS24, CBS127, CBS129 and CBS155 caused retardation of shoot growth at 10 d. Maximum nodule-promoting effect was observed with Bacillus strains CBS106, CBS127 and CBS155. The symbiotic effectiveness of Mesorhizobium sp. Cicer strain Ca181 was further improved on coinoculation with six Bacillus strains i.e. CBS9, CBS17, CBS20, CBS106, CBS127 and CBS155 at 80 d of plant growth under sterile conditions and shoot dry weight ratios increased 1.62 to 1.74 times those of Mesorhizobium-inoculated treatments, suggesting the usefulness of introduced rhizobacteria in improving crop productivity.     

Elicitation of systemic resistance and growth promotion of Arabidopsis thaliana by PGPRs from Nicotiana glauca: a study of the putative induction pathway

The ability of six putative plant growth promoting rhizobacteria, isolated from the rhizosphere of Nicotiana glauca L., to stimulate growth and induce systemic resistance against Xanthomonas campestris CECT 95 in Arabidopsis thaliana L. Col-0 was evaluated. The six bacterial strains significantly reduced the disease symptoms caused by the pathogen compared to the controls, with the best results obtained with the Bacillus strain N11.37 and the Stenotrophomonas strain N6.8. These two strains were tested on A. thaliana NahG plants and jar1-1 and etr1-1 mutants, to elucidate whether the salicylic acid (SA)-dependent or SA-independent pathway was involved in the induction of systemic resistance. The results indicate that N6.8 induces the SA-dependent pathway. For N11.37 it is as yet not clear as in the etr1-1 mutants and NahG plants ISR is not expressed, while in jar1-1 it is. In addition, levels of SA were measured in Col-0 plants treated with N6.8 and N11.37 to confirm whether or not the two strains produced an increased level of SA. N6.8- and N11.37-induced plants showed higher levels of SA than the controls. It is concluded that N6.8 induces a SA-dependent pathway while N11.37 induces a pathway that is both ethylene (ET)- and SA-dependent.     

Establishment of hairy root cultures ofDatura stramonium. Characterization and stability of tropane alkaloid production during long periods of subculturing

The aim of this paper was the screening of the variability of growth patterns, biomass and tropane alkaloid production of 500 hairy root lines ofDatura stramonium. Data on the long term stability in alkaloid production of these lines for more than 5 years are also provided. In an effort to obtain high alkaloid-producing root clones, it is demonstrated that systematic selection is necessary. Comparisons are made, mainly concerning alkaloid production and its stability, with normal root cultures initiated from the same mother plants when necessary. Hairy root cultures were found to have a hyoscyamine and scopolamine bioproductivity of 2 orders of magnitude higher than mother plants.     

Antimicrobial activities of rhizobacterial strains of <Emphasis Type="Italic">Pseudomonas</Emphasis> and <Emphasis Type="Italic">Bacillus strains</Emphasis> isolated from rhizosphere soil of carnation (<Emphasis Type="Italic">Dianthus caryophyllus</Emphasis> cv. Sunrise)

Under the present study, an attempt was made to characterize rhizobacteria i.e. Pseudomonas and Bacillus species isolated from rhizosphere of carnation to evaluate their growth promoting effect on carnation so as to select and develop more efficient indigenous plant growth promoting and disease suppressing bioagents of specific soil type and specific plant type. Maximum strains of Pseudomonas and Bacillus sp. showed significant antimicrobial activities against most of the microorganisms tested. On the basis of in vitro antagonistic activities, the best strains were selected and used in field trial to study the influence of these strains on the growth of carnation. Results have shown marked effect on growth parameters and disease incidence has also been reduced significantly.     

Activité néformatrice d'acides ribonucléiques extraits de tumeurs végétales

RNAs extracted from crown-gall tumors, induced by Agrobacterium tumefaciens (strain B6) on stems of Datura stramonium L., have been isolated by the phenol method and purified through Biogel P 60 columns. These RNAs have been transformed into complexes with l -amino acids by incubation in a medium containing: Tris HCI buffer, pH 7.6, ATP, MgCl₂, a mixture of l -amino acids and a polypeptide synthetase purified from Alcaligenes faecalis. The inoculation of stems of Datura plants with these complexes induces the development of nodular outgrowths, whereas other complexes made from RNAs isolated from healthy Datura plants, from Agrobacterium tumefaciens, Escherichia coli and Alcaligenes faecalis do not cause any hyperplasia under our experimental conditions. The analysis of the results obtained, supported by histological studies of the outgrowths, suggests that these neoformations should be of tumoral nature.     

Synthetic community with six Pseudomonas strains screened from garlic rhizosphere microbiome promotes plant growth

The rhizosphere microbiome plays an important role in the growth and health of many plants, particularly for plant growth-promoting rhizobacteria (PGPR). Although the use of PGPR could improve plant production, real-world applications are still held back by low-efficiency methods of finding and using PGPR. In this study, the structure of bacterial and fungal rhizosphere communities of Jinxiang garlic under different growth periods (resume growth, bolting and maturation), soil types (loam, sandy loam and sandy soil) and agricultural practices (with and without microbial products) were explored by using amplicon sequencing. High-efficiency top-down approaches based on high-throughput technology and synthetic community (SynCom) approaches were used to find PGPR in garlic rhizosphere and improve plant production. Our findings indicated that Pseudomonas was a key PGPR in the rhizosphere of garlic. Furthermore, SynCom with six Pseudomonas strains isolated from the garlic rhizosphere were constructed, which showed that they have the ability to promote plant growth.     

Growth promotion of <Emphasis Type="Italic">Xanthium italicum</Emphasis> by application of rhizobacterial isolates of <Emphasis Type="Italic">Bacillus aryabhattai</Emphasis> in microcosm soil

This study was conducted using rhizobacteria, which are able to exert beneficial effects upon plant growth in the infertile soil collected from barren lakeside areas. Four strains of plant growth promoting bacteria were isolated from the rhizosphere of a common wild plant, Erigeron canadensis. Isolated strains LS9, LS11, LS12, and LS15 were identified as Bacillus aryabhattai by 16S rDNA sequence analysis. B. aryabhattai LS9, LS11, LS12, and LS15 could solubilize 577.9, 676.8, 623.6, and 581.3 mg/L of 0.5% insoluble calcium phosphate within 2 days of incubation. Production of indole acetic acid, a typical growth promoting phytohormone auxin, by strain LS15 was 471.3 mg/L in 2 days with the addition of auxin precursor L-tryptophan. All the strains also produced other phytohormones such as indole butyric acid, gibberellins, and abscisic acid, and strain LS15 showed the highest production rate of gibberellin (GA₃), 119.0 μg/mg protein. Isolated bacteria were used in a microcosm test for growth of wild plant Xanthium italicum, which can be utilized as a pioneer plant in barren lands. Seed germination was facilitated, and the lengths of roots, and shoots and the dry weights of germinated seedlings after 16 days were higher than those of the uninoculated control plants. Root lengths of seedlings of X. italicum increased by 121.1% in LS11-treated samples after 16 days. This plant growth-promoting capability of B. aryabhattai strains may be utilized as an environmentally friendly means of revegetating barren lands, especially sensitive areas such as lakeside lands.     

Hippophae rhamnoides L. rhizobacteria exhibit diversified cellulase and pectinase activities

Hippophae rhamnoides L. provides an enormous range of medicinal and nutritional benefits. The significant abilities of this plant to survive in Himalayan high altitudes enticed our study to investigate its rhizosphere. Seventeen rhizobacterial strains were isolated from the rhizospheric soil and plant root nodules, belonging to genus Frankia, Azorhizobium, Bacillus, Paenibacillus, Brevibacillus and Pseudomonas, as identified by 16SrRNA sequencing. This varying bacterial population was further examined for the presence of root degrading enzymes pectinase and cellulase, which enable them to intrude the plant roots. Based on the growth and substrate utilization by these rhizobacteria on pectinase screening agar medium and Mandels and Reese agar medium, all the seventeen strains were identified as pectinase and cellulase producing rhizobacteria. The quantitative analysis by DNS method demonstrated varying enzyme activities, spot-lighting the physiological variation in the microbiome. The divergence in the enzyme activities shown by all the strains was analysed statistically, using the software ASSISTAT.

     

Effects of growth-promoting rhizobacteria on maize growth and rhizosphere microbial community under conservation tillage in Northeast China

Conservation tillage in conjunction with straw mulching is a sustainable agricultural approach. However, straw mulching reduces the soil temperature, inhibits early maize growth and reduces grain yield in cold regions. To address this problem, we investigated the effects of inoculation of plant growth-promoting rhizobacteria (PGPR) on maize growth and rhizosphere microbial communities under conservation tillage in Northeast China. The PGPR strains Sinorhizobium sp. A15, Bacillus sp. A28, Sphingomonas sp. A55 and Enterobacter sp. P24 were isolated from the maize rhizosphere in the same area and inoculated separately. Inoculation of these strains significantly enhanced maize growth, and the strains A15, A28 and A55 significantly increased grain yield by as much as 22%–29%. Real-time quantitative PCR and high-throughput sequencing showed that separate inoculation with the four strains increased the abundance and species richness of bacteria in the maize rhizosphere. Notably, the relative abundance of Acidobacteria_Subgroup_6, Chloroflexi_KD4-96, and Verrucomicrobiae at the class level and Mucilaginibacter at the genus level were positively correlated with maize biomass and yield. Inoculation with PGPR shows potential for improvement of maize production under conservation tillage in cold regions by regulating the rhizosphere bacterial community structure and by direct stimulation of plant growth.     

Plant growth-promoting rhizobacteria isolation from rhizosphere of submerged macrophytes and their growth-promoting effect on Vallisneria natans under high sediment organic matter load

Sediment organic matter is a key stressor for submerged macrophyte growth, which negatively impacts the ecological restoration of lakes. Plant growth-promoting rhizobacteria (PGPR) were screened from the rhizosphere of submerged macrophytes and used due to their promoting effect on Vallisneria natans under a high sediment organic matter load. Root exudates were used as the sole carbon source to obtain the root affinity strains. Eight isolates were selected from the 61 isolated strains, based on the P solubilization, IAA production, cytokinins production and ACC deaminase activity. The analysis of the 16S rDNA indicated that one strain was Staphylococcus sp., while the other seven bacterial strains were Bacillus sp. They were all listed in low-risk groups for safety use in agricultural practices. The plant height significantly increased after inoculation with PGPR strains, with the highest rate of increase reaching 96%. This study provides an innovative technique for recovering submerged macrophytes under sediment organic matter stress.     

Biocontrol and plant-growth-promoting capacities of actinobacterial strains from the Algerian Sahara and characterisation of Streptosporangium becharense SG1 as a promising biocontrol agent

Sixteen actinobacterial strains isolated from various ecological niches in the Algerian Sahara were screened for their biocontrol potential in root rot disease caused by Fusarium culmorum and their promotion of durum wheat growth. All actinobacteria were studied for in vitro antagonistic activity and plant-growth-promotion traits, for the production of cyanhydric acid, siderophores, chitinases and indole-3-acetic acid, and for the solubilisation of inorganic phosphate. Strongly antagonistic actinobacteria were selected for the biocontrol of F. culmorum in vivo and for the growth promotion of durum wheat plants in autoclaved and non-autoclaved soils. The Streptosporangium becharense strain SG1 exhibited remarkable positive results in all trials. Compared to untreated wheat seeds, the root rot severity index was decreased significantly (P?相似文献   

Screening for PGPR to improve growth of Cistus ladanifer seedlings for reforestation of degraded mediterranean ecosystems

A screening for PGPRs was carried out in the rhizosphere of wild populations of Cistus ladanifer. Two hundred and seventy bacteria were isolated, purified and grouped by morphological criteria. Fifty percent of the isolates were selected and tested for aminocyclopropanecarboxylic acid (ACC) degradation, auxin and siderophore production and phosphate solubilisation. Fifty-eight percent of the isolates showed at least one of the evaluated activities, with phosphate solubilisation and siderophore production being the most abundant traits. After PCR-RAPDs (Randomly amplified polymorphic DNA) analysis, 11 groups appeared with 85% similiarity, revealing the low diversity in the system. One strain of each group was tested in a biological assay, and those that enhanced Cistus growth were identified by 16S rDNA sequencing.Although seven of the 11 assayed strains were phosphate solubilisers and able to produce siderophores, only one was really effective in increasing all biometric parameters in Cistus ladanifer seedlings, the lack of effect of the other six probably being due to the rich substrate used. This suggests that other mechanisms apart from nutrient mobilisation might be involved in growth promotion by this strain. However, the low diversity together with the high redundancy detected by PCR-RAPDs and the predominance of strains able to mobilise nutrients in the rhizosphere of Cistus reveals that the plant selects for bacteria that can help to supply scarce nutrients. This type of plant growth promoting rhizobacteria (PGPR) strains should be succesful in reforestation practices.