Stabilization of dextransucrase from <Emphasis Type="Italic">Leuconostoc mesenteroides</Emphasis> NRRL B-640

Phosphate solubilizing yeast (PSY) were isolated from rhizosphere, non-rhizosphere and fruits from Bhavnagar district. The potential of 25 yeasts were analyzed on the basis of phosphate solubilizing zone to growth on solid medium denoted as solubilization index (SI) which ranged from 1.10 to 1.50. Among 25 yeast isolates, 6 yeast belonging to genus Saccharomyces (2), Hansenula, Klockera, Rhodotorula and Debaryomyces exhibited highest SI (1.33–1.50) were further examined for in vitro tricalcium phosphate (TCP) and low grade rock phosphate (RP) solubilization. TCP proved superior to RP with all the yeasts. Within low grade RPs tested, except isolate Y5, all isolates showed maximum solubilization with Hirapur RP (HRP) ranging from 7.24 to 19.30 mg% P₂O₅. Among six PSY screened, Debaryomyces hansenii showing maximal HRP solubilization was chosen for further physiological studies. Maximum HRP solubilization was expressed in following condition: pH optima 7.0, temperature optima 28°C and optimal period of incubation were 15 days. Acidic pH of the spent media was a constant feature in all the cases. No correlation could be established between final acidity produced by yeasts and the quantity of phosphate liberated.     

Establishment of phosphate-solubilizing strains of Azotobacter chroococcum in the rhizosphere and their effect on wheat cultivars under green house conditions

A pot experiment was conducted in the green house to investigate the establishment of phosphate solubilizing strains of Azotobacter chroococcum, including soil isolates and their mutants, in the rhizosphere and their effect on growth parameters and root biomass of three genetically divergent wheat cultivars (Triticum aestivum L.). Five fertilizer treatments were performed: Control, 90 kg N ha^—1, 90 kg N + 60 kg P₂O₅ ha^—1, 120 kg N ha^—1 and 120 kg N + 60 kg P₂O₅ ha^—1. Phosphate solubilizing and phytohormone producing parent soil isolates and mutant strains of A. chroococcum were isolated and selected by an enrichment method. In vitro phosphate solubilization and growth hormone production by mutant strains was increased compared with soil isolates. Seed inoculation of wheat varieties with P solubilizing and phytohormone producing A. chroococcum showed better response compared with controls. Mutant strains of A. chroococcum showed higher increase in grain (12.6%) and straw (11.4%) yield over control and their survival (12—14%) in the rhizosphere as compared to their parent soil isolate (P4). Mutant strain M37 performed better in all three varieties in terms of increase in grain yield (14.0%) and root biomass (11.4%) over control.     

Solubilization of organic and inorganic phosphates by three highly efficient soil bacterial isolates

Screening soil samples collected from a diverse range of slightly alkaline soil types, we have isolated 22 competent phosphate solubilizing bacteria (PSB). Three isolates identified as Pantoea agglomerans strain P5, Microbacterium laevaniformans strain P7 and Pseudomonas putida strain P13 hydrolyzed inorganic and organic phosphate compounds effectively. Bacterial growth rates and phosphate solubilization activities were measured quantitatively under various environmental conditions. In general, a close association was evident between phosphate solubilizing ability and growth rate which is an indicator of active metabolism. All three PSB were able to withstand temperature as high as 42°C, high concentration of NaCl upto 5% and a wide range of initial pH from 5 to 11 while hydrolyzing phosphate compounds actively. Such criteria make these isolates superior candidates for biofertilizers that are capable of utilizing both organic and mineral phosphate substrates to release absorbable phosphate ion for plants.     

一株耐盐日本曲霉的筛选及其溶磷促生作用

【目的】从内蒙古种植葵花的盐碱地中筛选高效溶磷真菌,为盐碱地增产节肥开发生物肥料提供溶磷菌种资源。【方法】利用ITS r DNA序列鉴定菌株、固体培养基测定耐盐性,液体摇床培养与盆栽试验结合分析菌株溶磷能力,盆栽和田间试验明确菌株M1促进作物生长和增产作用;LC-MS技术测定菌株M1在液体培养基中分泌有机酸和植物激素含量,明确菌株M1的溶磷和促生机理。【结果】溶磷菌株M1鉴定为日本曲霉(Aspergillus japonicus)。液体培养基接种菌株M1培养6 d,以Ca_3(PO_4)_2为磷源时上清液有效磷达1020.89 mg/L,溶解率为63.30%;以AlPO_4为磷源时有效磷达995.69 mg/L,溶解率为48.59%;以贵州开阳磷矿粉、江苏锦屏磷矿粉、云南晋宁磷矿粉、河北钒山磷矿粉和云南昆阳磷矿粉为磷源接种菌株M1,从晋宁磷矿粉释放的有效磷浓度最高,达到363.64 mg/L。菌株M1可耐受10%NaCl。将M1制备的菌剂分别接种于施用Ca_3(PO_4)_2、AlPO_4和开阳磷矿粉3种磷源的4种盆栽试验土壤包括北京石灰性潮土、安徽黏性潮土、安徽水稻土和山东沿海盐潮土。结果显示,菌株M1对玉米植株促生效果显著,玉米植株鲜重比对照提高2.14%–90.91%、干重增加22.15%–268.28%;土壤有效磷提高21.81–24.27 mg/kg。菌株M1与4种土壤的适配性均高于对照菌株DSM 821。田间小区花生产量结果显示,接种溶磷菌剂M1增产效果最好,花生果实产量达4.46 t/hm~2,比不接种菌剂的对照处理增加0.81 t/hm~2,增产22.19%。菌株M1在含有磷酸三钙、磷酸铝和开阳磷矿粉3种难溶磷培养液中经过6 d培养,均产生7种有机酸,其中草酸和柠檬酸含量最高,分别为616.16 mg/L和413.69 mg/L;培养液均能检测到吲哚乙酸(IAA)和玉米素,IAA含量为15.45–77.58 mg/L,玉米素浓度为0.06–0.11 mg/L。【结论】获得了一株高效溶解多种难溶磷的日本曲霉菌M1,它能显著增加土壤有效磷、促进玉米生长和花生增产,与4种典型土壤适配性好,具有良好的农业应用前景。     

Solubilization of rock phosphates byRhizobium andBradyrhizobium

The ability ofRhizobium andBradyrhizobium strains to solubilize phosphate from hydroxyapatite was determined in a medium containing NH₄Cl or KNO₃. The presence of NH₄ ⁺ in the medium resulted in higher solubilization of phosphate as compared to the presence of KNO₃, with the exception ofR. leguminosarium bv. viceae strain TAL 1236 and 1402 which solubilized comparable amounts of phosphate in a medium containing either KNO₃ or NH₄Cl. These results suggest that the strains employ two different mechanisms for phosphate solubilization, one depending on the presence of NH₄ ⁺, the other not requiring its presence. Temperature and aeration (O₂ demand) optima were 30°C and 4.2 Hz (shaking frequency), respectively. In nonsterile soil the tested strain (R. meliloti TAL 1236) was very effective in solubilizing rock phosphate.     

Phosphate solubilization and growth promotion by <Emphasis Type="Italic">Pseudomonas fragi</Emphasis> CS11RH1 (MTCC 8984), a psychrotolerant bacterium isolated from a high altitude Himalayan rhizosphere

Phosphate solubilization and growth promotion by Pseudomonas fragi CS11RH1 (MTCC 8984), a psychrotolerant bacterium isolated from a high altitude garlic rhizosphere from the Indian Himalayas, are reported here. The identity of the isolate was arrived on the basis of its biochemical features and sequencing of the 16S rRNA gene. The isolate grew and solubilized phosphate at temperatures ranging from 4 to 30°C. Besides solubilizing P it produced indole acetic acid (IAA) and hydrogen cyanide (HCN). Seed bacterization with the isolate significantly increased the percent germination, rate of germination, plant biomass and nutrient uptake of wheat seedlings. While Pseudomonas fragi is normally associated with the spoilage of dairy products stored at cold temperatures, this is an early report on the plant growth promoting ability of the bacterium.     

Simultaneous phosphate solubilization potential and antifungal activity of new fluorescent pseudomonad strains, Pseudomonasaeruginosa, P. plecoglossicida and P. mosselii

Of 80 fluorescent pseudomonad strains screened for phosphate solubilization, three strains (BFPB9, FP12 and FP13) showed the ability to solubilize tri-calcium phosphate (Ca₃(PO₄)₂). During mineral phosphate solubilization, decrease of pH in the culture medium due to the production of organic acids by the strains was observed. These phosphate solubilizing strains produced indole-3-acetic acid (IAA) and protease as well as exhibited a broad-spectrum antifungal activity against phytopathogenic fungi. When tested in PCR using the gene-specific primers, strain BFPB9 showed the presence of hcnBC genes that encode hydrogen cyanide. On the basis of phenotypic traits, 16S rRNA sequence homology and subsequent phylogenetic analysis, strains BFPB9, FP12 and FP13 were designated as Pseudomonas aeruginosa, P. plecoglossicida and P. mosselii, respectively. Present investigation reports the phosphate solubilization potential and biocontrol ability of new strains that belong to P. plecoglossicida and P. mosselii. Because of the innate potential of phosphate solubilization, production of siderophore, IAA, protease, cellulase and HCN strains reported in this study can be used as biofertilizers as well as biocontrol agents.     

A study of the growth condition and solubilization of phosphate from hydroxyapatite byPantoea agglomerans

The growth conditions ofPantoea agglomerans, a phosphate solubilizing organism, were studied in our laboratory to determine the optimal conditions.Pantoea agglomerans showed the highest growth rate at 30°C, pH 7.0 and 2 vvm, after 50 h cultivation. A certain relationship between pH and phosphate concentration, was evident when the glucose concentration in the medium was changed. Increasing glucose concentration increased the pH buffer action of the broth. At glucose concentrations higher than the optimum concentration of 0.2 M, the cell growth was retarded.P. agglomerans consumed glucose as a substrate to produce organic acids which caused the pH decrease in the culture medium. The phosphate concentration in the medium was increased by the presence of the organic acids, which solubilized insoluble phosphates such as hydroxyapatite.     

Characterization of plant growth-promoting rhizobacterium <Emphasis Type="Italic">Exiguobacterium</Emphasis> NII-0906 for its growth promotion of cowpea (<Emphasis Type="Italic">Vigna unguiculata</Emphasis>)

A phosphate solubilizing and antagonistic bacterial strain, isolated from a Western Ghat forest soil in Kerala province, India (designated as NII-0906), showed cold tolerance and grew from 10 to 37°C (optimum temperature 30°C). It was a Gram-positive, rod shaped, 0.8–1.6 μm in size, and exhibited tolerance to a wide pH range (5–12; optimum 7.0) and salt concentration up to 7% (w/v). The isolate showed maximum similarity with Exiguobacterium marinum TF-80^T based on 16S rRNA analysis. It solubilized tricalcium phosphate under in vitro conditions. The phosphate solubilization was estimated along a temperature range (5–40°C), and maximum activity (84.7 μg mL⁻¹ day⁻¹) was recorded at 30°C after 10 days of incubation. The phosphate solubilizing activity coincided with a concomitant decrease in pH of the medium. The isolate also exhibited antifungal activity against phytopathogenic fungi in Petri dish assays and produced siderophore and hydrogen cyanide. The strain’s plant growth promotion properties were demonstrated through a cowpea-based bioassay under greenhouse conditions. The bacterial inoculation resulted in significant increment in plant root, stem and as well as in plant biomass. Further, scanning electron microscopic study revealed the root colonization in cowpea. These results could offer potential perspective for the strain to be used as plant growth-promoting rhizobacteria, which could be used as an inoculant for regional crops.     

Performance evaluation of potent phosphate solubilizing bacteria in potato rhizosphere

Three phosphate solubilizing bacterial isolates identified as Pantoea agglomerans strain P5, Microbacterium laevaniformans strain P7 and Pseudomonas putida strain P13 were assessed for mutual relationships among them, competitiveness with soil microorganisms and associations with plant root using luxAB reporter genes for follow-up studies. Synergism between either P. agglomerans or M. laevaniformans, as acid-producing bacteria, and P. putida, as a strong phosphatase producer, was consistently observed both in liquid culture medium and in root rhizosphere. All laboratory, greenhouse and field experiments proved that these three isolates compete well with naturally occurring soil microorganisms. Consistently, the combinations of either P. agglomerans or M. laevaniformans strains with Pseudomonas putida led to higher biomass and potato tuber in greenhouse and in field trials. It is conceivable that combinations of an acid- and a phosphatase-producing bacterium would allow simultaneous utilization of both inorganic and organic phosphorus compounds preserving the soil structure.     

Effect of Abiotic Stress on Phosphate Solubilization by Biocontrol Fungus <Emphasis Type="Italic">Trichoderma</Emphasis> sp.

This study was undertaken to explore the role of Trichoderma sp. in phosphate (P) solubilization and antagonism against fungal phytopathogens. All fungal isolates (SE₆, KT₆, KT₂₈, and BRT₁₁) and a standard culture of T. harzianum (Th-std) were able to antagonize two fungal phytopathogens (Sclerotium rolfsii and Rhizoctonia solani) of chickpea (Cicer arietinum L.) wilt complex. Transmission electron microscopic studies (TEM) further confirmed ultra-cytological changes in the sclerotia of S. rolfsii parasitized by Trichoderma sp. All fungal cultures exhibited production of NH₃ and siderophore, but only BRT₁₁, SE₆, and Th-std could produce HCN. Among all the cultures tested, isolate KT₆ was found to be most effective for solubilization of ferric phosphate releasing 398.4 μg ml⁻¹ phosphate while isolates BRT₁₁ and SE₆ showed more potential for tricalcium phosphate (TCP) solubilization releasing 449.05 and 412.64 μg ml⁻¹ phosphate, respectively, in their culture filtrates. Part of this study focused on the influence of abiotic stress conditions such as pH, temperature, and heavy metal (cadmium) on phosphate (TCP) solubilizing efficiency. Two selected cultures KT₆ and T. harzianum retained their P solubilizing potential at varying concentrations of cadmium (0–1000 μg ml⁻¹). Isolate KT₆ and standard culture of T. harzianum released 278.4 and 287.6 μg ml⁻¹ phosphate, respectively, at 1000 μg ml⁻¹cadmium. Maximum solubilization of TCP was obtained at alkaline pH and at 28°C temperature. Isolate BRT₁₁ was found most alkalo-tolerant releasing 448.0 μg ml⁻¹ phosphate at pH 9.     

Pseudomonas corrugata (NRRL B-30409) Mutants Increased Phosphate Solubilization, Organic Acid Production, and Plant Growth at Lower Temperatures

A study for screening and selection of mutants of Pseudomonas corrugata (NRRL B-30409) based on their phosphate solubilization ability, production of organic acids, and subsequent effect on plant growth at lower temperatures under in vitro and in situ conditions was conducted. Of a total 115 mutants tested, two (PCM-56 and PCM-82) were selected based on their greater phosphate solubilization ability at 21°C in Pikovskaya’s broth. The two mutants were found more efficient than wild-type strain for phosphate solubilization activity across a range of temperature from psychotropic (4°C) to mesophilic (28°C) in aerated GPS medium containing insoluble rock phosphate. High-performance liquid chromatography analysis showed that phosphate solubilization potential of wild-type and mutant strains were mediated by production of organic acids in the culture medium. The two efficient mutants and the wild strain oxidized glucose to gluconic acid and sequentially to 2-ketogluconic acid. Under in vitro conditions at 10°C, the mutants exhibited increased plant growth as compared to wild type, indicating their functionality at lower temperatures. In greenhouse trials using sterilized soil amended with either soluble or rock phosphate, inoculation with mutants showed greater positive effect on all of the growth parameters and soil enzymatic activities. To the best of our knowledge, this is the first report on the development of phosphate solubilizing mutants of psychotropic wild strain of P. corrugata, native to the Indian Himalayan region.     

Phosphate-solubilization mechanism and in vitro plant growth promotion activity mediated by Pantoea eucalypti isolated from Lotus tenuis rhizosphere in the Salado River Basin (Argentina)

Aims: To isolate and characterize phosphate‐solubilizing strains from a constrained environment such as the Salado River Basin and to assess their phosphate‐solubilizing mechanisms, to further selection of the most promising strains to inoculate and improve the implantation and persistence of Lotus tenuis in the most important area devoted to meat‐cow production in Argentina. Methods and Results: Fifty isolates were obtained and through BOX‐PCR analysis, 17 non‐redundant strains were identified. Subsequently, they were found to be related to Pantoea, Erwinia, Pseudomonas, Rhizobium and Enterobacter genera, via 16S rRNA gene sequence analysis. This was in agreement with the clusters obtained by antibiotic resistance analysis. All isolates were tested for their phosphate‐solubilizing activity and selected strains were inoculated onto L. tenuis plants. The most efficient isolate, was identified as Pantoea eucalypti, a novel species in terms of plant growth‐promoting rhizobacteria. Conclusions: The isolates obtained in this study showed a significant in vitro plant‐growth promoting activity onto Lotus tenuis and the best of them solubilizes phosphate mainly via induction of the metabolism through secretion and oxidation of gluconic acid. Singnificance and Impact of the Study: The use of these bacteria as bioinoculants, alone or in combination with nitrogen‐fixing micro‐organisms, could be a sustainable practice to facilitate the nutrient supply to Lotus tenuis plants and preventing negative side‐effects such as eutrophication.     

Medium pH, carbon and nitrogen concentrations modulate the phosphate solubilization efficiency of Penicillium purpurogenum through organic acid production

Aims: To study phosphate solubilization in Penicillium purpurogenum as function of medium pH, and carbon and nitrogen concentrations. Methods and Results: Tricalcium phosphate (CP) solubilization efficiency of P. purpurogenum was evaluated at acid or alkaline pH using different C and N sources. Glucose‐ and (NH₄)₂SO₄‐based media showed the highest P solubilization values followed by fructose. P. purpurogenum solubilizing ability was higher in cultures grown at pH 6·5 than cultures at pH 8·5. Organic acids were detected in both alkaline and neutral media, but the relative percentages of each organic acid differed. Highest P release coincided with the highest organic acids production peak, especially gluconic acid. When P. purpurogenum grew in alkaline media, the nature and concentration of organic acids changed at different N and C concentrations. A factorial categorical experimental design showed that the highest P‐solubilizing activity, coinciding with the highest organic acid production, corresponded to the highest C concentration and lowest N concentration. Conclusions: The results described in the present study show that medium pH and carbon and nitrogen concentrations modulate the P solubilization efficiency of P. purpurogenum through the production of organic acids and particularly that of gluconic acid. In the P solubilization optimization studies, glucose and (NH₄)₂SO₄ as C and N sources allowed a higher solubilization efficiency at high pH. Significance and Impact of the Study: This organism is a potentially proficient soil inoculant, especially in P‐poor alkaline soils where other P solubilizers fail to release soluble P. Further work is necessary to elucidate whether these results can be extrapolated to natural soil ecosystems, where different pH values are present. Penicillium purpurogenum could be used to develop a bioprocess for the manufacture of phosphatic fertilizer with phosphate calcium minerals.     

Inoculation with Pseudomonas putida PCI2, a phosphate solubilizing rhizobacterium,stimulates the growth of tomato plants

The use of phosphate solubilizing plant growth-promoting microorganisms as inoculants assists in the hydrolysis of insoluble forms of phosphorus leading to increased plant growth. Pseudomonas putida PCI2 was evaluated for phosphatase activity and solubilization of AlPO₄ and FePO₄. The effect of different incubation temperatures, concentrations of NaCl and different pH on growth of PCI2 and P solubilization was studied. PCI2 proved to be positive for phosphatase activity, solubilized AlPO₄ and hydrolyzed Ca₃(PO₄)₂ even in medium with 5 % NaCl. In addition, PCI2 produced 45 % units of siderophores. The production of IAA by PCI2 was stimulated in vitro by the addition of different concentrations of L-tryptophan to the culture medium. Assays with tomato seedlings showed that the length of the root was reduced as the concentration of IAA increased. On the other hand, inoculation with PCI2 caused a clear growth-promoting effect on shoot growth in the presence of L-tryptophan. P. putida PCI2 is adapted to different environmental conditions and has potential to be developed and used as an inoculant for increasing the growth of tomato plants.     

Biological nitrogen fixation and phosphate solubilization by bacteria isolated from tropical soils

Introduction

In addition to fixing atmospheric nitrogen, some bacterial isolates can also solubilize insoluble phosphates, further contributing to plant growth.

Aims

The objectives of this study were the following: isolate, select, and identify nodulating bacteria in the cowpea that are efficient not only in biological nitrogen fixation (BNF) but also in the solubilization of insoluble inorganic phosphates; identify and quantify the organic acids produced; and establish the relationship between those acids and the solubilizing capacity.

Methods

The bacteria were captured from two soils containing high concentrations of insoluble phosphorus from the cities of Lavras and Patos de Minas, using the cowpea [Vigna unguiculata (L.) Walp.] as bait. We obtained 78 strains, which were characterized according to their cultural attributes in culture medium 79 with the strains UFLA 03-84, INPA 03-11B, and BR3267 (approved by the Ministry of Livestock and Supply Agriculture—MAPA, as inoculants for the cowpea) and Burkholderia cepacia (LMG1222^T), which was used as a positive control for phosphate solubilization. Strains that were selected for their efficiency in both processes were identified by 16S rDNA sequence analysis. We evaluated the symbiotic efficiency (BNF) in a greenhouse and the solubilization efficiency of CaHPO₄, Al(H₂PO₄)₃, and FePO₄.2H₂O in solid and liquid GELP media. Strains that excelled at the solubilization of these phosphate sources were also evaluated for the production of the following organic acids: oxalic, citric, gluconic, lactic, succinic, and propionic.

Results

The presence of Acinetobacter, Bacillus, Firmicutes, Microbacterium, Paenibacillus, and Rhizobium was detected by 16S rDNA sequencing and analysis. Bacterial strains obtained from cowpea nodules varied greatly in the efficiency of their BNF and phosphate solubilization processes, especially in the strains UFLA 03-09, UFLA 03-10, UFLA 03-12, and UFLA 03-13, which were more efficient in both processes. More strains were able to solubilize insoluble inorganic calcium and iron phosphates in liquid medium than in solid medium. The production of organic acids was related to the solubilization of CaHPO₄ and FePO₄.2H₂O for some strains, and the type and concentration of the acid influenced this process.

Conclusions

These are the first results obtained with bacterial isolates from tropical soils in which the production of organic acids was detected and quantified to examine the solubilization of insoluble inorganic phosphates.     

Solubilization of insoluble inorganic phosphates by a novel temperature-, pH-, and salt-tolerant yeast, <Emphasis Type="Italic">Rhodotorula</Emphasis> sp<Emphasis Type="Italic">.</Emphasis> PS4, isolated from seabuckthorn rhizosphere,growing in cold desert of Ladakh,India

The study was aimed to develop biofertilizer solubilizing inorganic phosphates for region experiencing temperature, pH and salt stressed conditions. A yeast strain PS4, which was temperature-, pH- and salt-tolerant and capable of solubilizing insoluble inorganic phosphate was isolated from rhizosphere of seabuckthorn (Hippophae rhamnoides L.), growing in the Indian Trans-Himalaya. Based on morphological, biochemical, whole cell FAME analysis and molecular characterization, strain PS4 was identified as Rhodotorula sp. The soluble phosphate production under optimal conditions at pH 7 and 30°C was 278.3 mg l⁻¹. Strain PS4 showed ability to solubilize insoluble phosphate under different stress conditions viz. 5–40°C temperature, 1–5% salt concentration and 3–11 pH range. Soluble phosphate production from Ca₃(PO₄)₂ under combined stress conditions at extreme values of temperature, pH and salt concentration showed 81.6–83.2% reduction as compare to optimal conditions after 5 days incubation. The strain solubilize Ca₃(PO₄)₂ to a great extent than FePO₄ and AlPO₄. The solubilization of insoluble phosphate was associated with drop in pH of the culture media. Inoculation of tomato seedling with the strain increased fruit yield, roots and shoot length. Rhodotorula sp. PS4 with phosphate-solubilizing ability under stress conditions appeared to be attractive for exploring their plant growth-promoting activity towards the development of microbial inoculants in stressed region.     

Rhizosphere competent <Emphasis Type="Italic">Pantoea agglomerans</Emphasis> enhances maize (<Emphasis Type="Italic">Zea mays</Emphasis>) and chickpea (<Emphasis Type="Italic">Cicer arietinum</Emphasis> L.) growth,without altering the rhizosphere functional diversity

Plant growth promoting Pantoea agglomerans NBRISRM (NBRISRM) was able to produce 60.4 μg/ml indole acetic acid and solubilize 77.5 μg/ml tri-calcium phosphate under in vitro conditions. Addition of 2% NaCl (w/v) in the media induced the IAA production and phosphate solubilization by 11% and 7%, respectively. For evaluating the plant growth promotory effect of NBRISRM inoculation a micro plot trial was conducted using maize and chickpea as host plants. The results revealed significant increase in all growth parameters tested in NBRISRM inoculated maize and chickpea plants, which were further confirmed by higher macronutrients (N, P and K) accumulation as compared to un-inoculated controls. Throughout the growing season of maize and chickpea, rhizosphere population of NBRISRM were in the range 10⁷–10⁸ CFU/g soil and competing with 10⁷–10⁹ CFU/g soil with heterogeneous bacterial population. Functional richness, diversity, and evenness were found significantly higher in maize rhizosphere as compared to chickpea, whereas NBRISRM inoculation were not able to change it, in both crops as compared to their un-inoculated control. To the best of our knowledge this is first report where we demonstrated the effect of P. agglomerans strain for improving maize and chickpea growth without altering the functional diversity.     

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...     

Organic acid production in vitro and plant growth promotion in maize under controlled environment by phosphate-solubilizing fluorescent Pseudomonas

Background  

Phosphorus deficiency is a major constraint to crop production due to rapid binding of the applied phosphorus into fixed forms not available to the plants. Microbial solubilization of inorganic phosphates has been attributed mainly to the production of organic acids. Phosphate-solubilizing microorganisms enhance plant growth under conditions of poor phosphorus availability by solubilizing insoluble phosphates in the soil. This paper describes the production of organic acids during inorganic phosphate solubilization and influence on plant growth as a function of phosphate solubilization by fluorescent Pseudomonas.