Genome Sequence of the Plant Growth-Promoting Rhizobacterium Bacillus sp. Strain 916

Bacillus sp. strain 916, isolated from the soil, showed strong activity against Rhizoctonia solani. Here, we present the high-quality draft genome sequence of Bacillus sp. strain 916. Its 3.9-Mb genome reveals a number of genes whose products are possibly involved in promotion of plant growth or antibiosis.     

Endophytic colonization of balloon flower by antifungal strain Bacillus sp. CY22

Endophytic Bacillus sp. CY22 was previously isolated from the root interior of the balloon flower (Platycodon grandiflorum) (Cho et al., Biosci. Biotechnol. Biochem., 66, 1270-1275 (2002)). Three-month-old balloon flower seedlings were inoculated with 10(7) cfu/ml of strain CY22R3, a rifampicin-resistant strain of CY22, and external and internal root colonization was assessed 2 and 4 weeks later. After inoculation, large numbers of bacteria were observed on the root surface by scanning electron microscopy. More detailed studies using optical and transmission electron microscopy confirmed that Bacillus sp. CY22 was endophytically established within intercellular spaces, cortical cells, and aerenchymas of root. Also, Bacillus sp. CY22 showed antibiotic activities against several phytopathogens by producing the antibiotic iturin A. In the pot test, root rot of balloon flower seedlings caused by Rhizoctonia solani was suppressed when the Bacillus sp. CY22R3 was inoculated into the soil.     

The effect of Penicillium fungi on plant growth and phosphorus mobilization in neutral to alkaline soils from southern Australia

The phosphate solubilizing fungi Penicillium radicum, Penicillium bilaiae (strain RS7B-SD1), and an unidentified Penicillium sp. designated strain KC6-W2 were tested for their ability to increase the growth and phosphorus (P) nutrition of wheat, medic, and lentil in three soils of neutral to alkaline pH reaction. The strongest plant growth promoting (PGP) strain was Penicillium sp. KC6-W2, which stimulated significant increases in shoot growth and dry mass in seven of the nine experiments conducted. Levels of PGP by Penicillium sp. KC6-W2 ranged from 6.6% to 19% and were associated with increased uptake of P to the shoot. The PGP properties of Penicillium sp. KC6-W2 were evident on each of the three different plant species and soil types, a level of reliability not observed in other strains tested. Inoculation of seed with P. radicum increased lentil growth by 5.5% (P < 0.05) in soil from Tarlee but did not affect plant growth in the eight other experiments. Inoculation of plant seed with P. bilaiae RS7B-SD1 resulted in significant PGP in two of the nine experiments conducted. However, when significant, stimulation of PGP by P. bilaiae RS7B-SD1 was strong and resulted in increases in medic dry matter (19%) and lentil shoot dry matter (15%). A soil microcosm experiment investigated the effect of Penicillium fungi on cycling of soil P. Penicillium bilaiae RS7B-SD1 was the only fungus to significantly increase HCO3-extractable P (23% increase; P < 0.05). Production of phosphatase enzymes was not associated with increased HCO3-extractable P. Addition of carbon in the form of ryegrass seed significantly increased microbial respiration and movement of P to the microbial biomass (P < 0.05), but these parameters were irrespective of Penicillium treatment. This work has established the potential for use of Penicillium inoculants to increase plant growth on alkaline soils in Australia. The role of Penicillium fungi in plant P uptake and soil P cycling requires further exploration.     

Plant growth promoting potential of free-living diazotrophs and other rhizobacteria isolated from Northern Indian soil

The viable count of free-living diazotrophic bacteria in different crop rhizospheres varied from 1.11 x 10(4) to 8.5 x 10(5) CFU/g of soil. The majority of the diazotrophs phenotypically belong to either Azotobacter chroococcum, non-A. chroococcum type and to a heterogenous group tentatively named putative nitrogen-fixing (PNF) bacteria. In this study, 25 isolates of the PNF group were screened for their multiple plant growth-promoting (PGP) traits and grouped into 5 PGP types. An isolate, PNF(11) showed promising PGP potential in vitro and was characterized as a species of Achromobacter by 16S rRNA analysis. The isolate PNF(11) along with three other previously isolated PGP bacteria, Azotobacter sp. (AZS(3)), fluorescent pseudomonas (Ps(5)), Bacillus sp. (Bc(1)) were selected for crop inoculation response in green house experiment on Vigna radiata var.T44. Plants from inoculated and control pots were sampled and analyzed at 30, 45 and 60 days after sowing for various vegetative, nodule-related data and yield parameters. The findings indicated that selected isolate of PNF bacteria, and other PGP isolates with multiple activities significantly improve the plant growth parameters, yield parameters of Vigna radiata T44 over control and also show good compatibility with Bradyrhizobium inoculation.     

Salt Stress Mitigating Potential of Halotolerant/Halophilic Plant Growth Promoting

Abstract

In the current study, the PGP (production of siderophore and IAA, fixation of nitrogen and solubilization of phosphate) potential of forty-five bacterial isolates comprising sixteen genera (Marinibacillus, Zhihengliuella, Bacillus, Nesterenkonia, Halobacillus, Promicromonospora, Terribacillus, Jeotgalibacillus, Staphylococcus, Oceanobacillus, Virgibacillus, Halomonas, Gracilibacillus, Planococcus, Thalassobacillus and Microbacterium) was investigated. Among these forty-five bacterial isolates, most of the isolates (40 isolates) possess plant growth promoting potential. Four bacterial isolates [Marinibacillus sp. (EM1), Zhihengliuella salsuginis (EM30), Planococcus sp. (EK9), and Promicromonospora sp. (EK12)] possessing PGP traits were applied on the barley grown under salt (NaCl) stress in a hydroponic system. Comparing to the un-inoculated group, all the four bacterial isolates significantly improved plant growth that inhibited with NaCl (200?mM) stress. The growth rate of the plants inoculated with Zhihengliuella salsuginis (EM30), Promicromonospora sp. (EK12), Planococcus sp. (EK9), and Marinibacillus sp. (EM1) was 81.86, 80.51, 70.62 and 69.22, respectively. As far as we know, this is the first report showing the PGP potential of Marinibacillus sp. (EM1), Bacillus horikoshii (EM9), Bacillus patagoniensis (EM12), Bacillus agaradhaerens (EK13), Oceanobacillus profundus (EM26) Thalassobacillus devorans (EM34) and Promicromonospora sp. (EK12).     

Isolation and characterization of endophytic Streptomyces strains from surface-sterilized tomato (Lycopersicon esculentum) roots

AIMS: To isolate endophytic Streptomyces strains from tomato and examine their antimicrobial activity. METHODS: Endophytic Streptomyces strains were isolated using surface-sterilization methods and identified by morphological characteristics. Antimicrobial activities were measured by the agar plate sensitivity method. Antifungal activity in vivo was measured by seedling mortality in infested soils. RESULTS: Twenty-one per cent of endophytic streptomycete isolates produced antibacterial metabolites and 41% produced antifungal metabolites in S medium. Sixty-five per cent of the most frequently isolated strains inhibited the growth of Rhizoctonia solani by the antibiosis assay but only 32% produced metabolites active against R. solani in S medium. Growth promotion and enhanced disease resistance of seedlings inoculated with Streptomyces sp. strain S30 were observed in tomato but not in cucumber seedlings. CONCLUSIONS: Endophytic Streptomyces spp. strains were successfully isolated using stringent methods and strain S30 promoted growth and enhanced resistance to R. solani in tomato seedlings. SIGNIFICANCE AND IMPACT OF THE STUDY: Endophytic streptomycetes showing antifungal activity in vitro and in vivo may indicate the potential for their use as biocontrol agents particularly of R. solani disease of tomato seedlings.     

Rhizoctonia wilt suppression of brinjal (Solanum melongena L) and plant growth activity by Bacillus BS2

An antibiotic-producing and hydrogen-cyanide-producing rhizobacteria strain Bacillus BS2 showed a wide range of antifungal activity against many Fusarium sp. and brinjal wilt disease pathogen Rhizoctonia solani. Seed bacterization with the strain BS2 promoted seed germination and plant growth in leguminous plants Phaseolus vulgaris and non-leguminous plants Solanum melongena L, Brassica oleracea var. capitata, B. oleraceae var. gongylodes and Lycopersicon esculentum Mill in terms of relative growth rate, shoot height, root length, total biomass production and total chlorophyll content of leaves. Yield of bacterized plants were increased by 10 to 49% compared to uninoculated control plants. Brinjal sapling raised through seed bacterization by the strain BS2 showed a significantly reduced wilt syndrome of brinjal caused by Rhizoctonia solani. Control of wilt disease by the bacterium was clue to the production of antibiotic-like substances, whereas plant growth-promotion was due to the activity of hydrogen cyanide. Root colonization study confirmed that the introduced bacteria colonized the roots and occupied 23-25% of total aerobic bacteria, which was confirmed using dual antibiotic (nalidixic acid and streptomycin sulphate) resistant mutant strain. The results obtained through this investigation suggested the potentiality of the strain BS2 to be used as a plant growth promoter and suppressor of wilt pathogen.     

Evaluation of Nostoc strain ATCC 53789 as a potential source of natural pesticides

The cyanobacterium Nostoc strain ATCC 53789, a known cryptophycin producer, was tested for its potential as a source of natural pesticides. The antibacterial, antifungal, insecticidal, nematocidal, and cytotoxic activities of methanolic extracts of the cyanobacterium were evaluated. Among the target organisms, nine fungi (Armillaria sp., Fusarium oxysporum f. sp. melonis, Penicillium expansum, Phytophthora cambivora, P. cinnamomi, Rhizoctonia solani, Rosellinia, sp., Sclerotinia sclerotiorum, and Verticillium albo-atrum) were growth inhibited and one insect (Helicoverpa armigera) was killed by the extract, as well as the two model organisms for nematocidal (Caenorhabditis elegans) and cytotoxic (Artemia salina) activity. No antibacterial activity was detected. The antifungal activity against S. sclerotiorum was further studied with both extracts and biomass of the cyanobacterium in a system involving tomato as a host plant. Finally, the herbicidal activity of Nostoc strain ATCC 53789 was evaluated against a grass mixture. To fully exploit the potential of this cyanobacterium in agriculture as a source of pesticides, suitable application methods to overcome its toxicity toward plants and nontarget organisms must be developed.     

Screening and evaluation of antiparasitic and in vitro anticancer activities of Panamanian endophytic fungi

Many compounds produced by fungi have relevant pharmaceutical applications. The purpose of this study was to collect and isolate endophytic fungi from different regions of Panama and then to test their potential therapeutic activities against Leishmania donovani, Plasmodium falciparum, and Trypanosoma cruzi as well as their anticancer activities in MCF-7 cells. Of the 25 fungal isolates obtained, ten of them had good anti-parasitic potential, showing selective activity against L. donovani; four had significant anti-malarial activity; and three inhibited the growth of T. cruzi. Anticancer activity was demonstrated in four isolates. Of the active isolates, Edenia sp. strain F0755, Xylaria sp. strain F1220, Aspergillus sp. strain F1544, Mycoleptodiscus sp. strain F0194, Phomopsis sp. strain F1566, Pycnoporus sp. strain F0305, and Diaporthe sp. strain F1647 showed the most promise based on their selective bioactivity and lack of toxicity in the assays.     

PhoR/PhoP two component regulatory system affects biocontrol capability of Bacillus subtilis NCD-2

The Bacillus subtilis strain NCD-2 is an important biocontrol agent against cotton verticillium wilt and cotton sore shin in the field, which are caused by Verticillium dahliae Kleb and Rhizoctonia solani Kuhn, respectively. A mutant of strain NCD-2, designated M216, with decreased antagonism to V. dahliae and R. solani, was selected by mini-Tn10 mutagenesis and in vitro virulence screening. The inserted gene in the mutant was cloned and identified as the phoR gene, which encodes a sensor kinase in the PhoP/PhoR two-component system. Compared to the wild-type strain, the APase activities of the mutant was decreased significantly when cultured in low phosphate medium, but no obvious difference was observed when cultured in high phosphate medium. The mutant also grew more slowly on organic phosphate agar and lost its phosphatidylcholine-solubilizing ability. The suppression of cotton seedling damping-off in vivo and colonization of the rhizosphere of cotton also decreased in the mutant strain when compared with the wild type strain. All of these characteristics could be partially restored by complementation of the phoR gene in the M216 mutant.     

THE ANTIBIOTIC ACTION OF BACILLUS SUBTILIS IN RELATION TO CERTAIN PARASITIC FUNGI, WITH SPECIAL REFERENCE TO ALTERNARIA SOLANI (ELL. & MART.) JONES & GROUT

The culture filtrate of a strain of Bacillus subtilis is shown to be antagonistic to the growth of Rhizoctonia solani, R. bataticola, Alternaria solani, Botrytis cinerea, Fusarium udum , and Colletotrichum falcatum , exhibiting specificity of action. Malformation of the germ tube of Alternaria solani spores resulting in 'bulb' formation is also reported. Diffusion of the antibiotic principle inside host tissues is indicated.     

植物根际促生菌的筛选及鉴定

【目的】植物根际促生菌(PGPR)和植物的互作关系往往不稳定,PGPR菌群有可能提高菌株对野外环境的适应性。为此,本文根据PGPR促生机制的多样性,从不同植物根际土壤进行了PGPR的筛选及鉴定。【方法】首先,按照固氮、解磷、解钾、拮抗6种常见病原真菌,同时能在植物根际定殖为基本初筛标准,然后在实验室条件下测定初筛菌株的多项促生能力(PGP),最后通过生理生化试验和16SrRNA基因序列分析对所筛菌株进行鉴定。【结果】从江苏扬州、盐城等地土壤样品筛选出14株PGPR,具有体外抑菌、产NH3、产IAA、产HCN、产嗜铁素、解磷、溶钾、固氮以及产抗生素等促生能力。分类鉴定结果显示:7株属于假单胞菌属(Pseudomonas)、3株属于类芽孢杆菌属(Paenibacillus)、2株为芽孢杆菌属(Bacillus)、1株为布克霍尔德氏菌属(Burkholderia)、1株为欧文氏菌属(Erwinia)。【结论】所筛细菌具有多种促生能力,且能在根际定殖,为进一步构建多功能PGPR广适菌群提供菌株资源。     

Alleviating salt stress in tomato seedlings using Arthrobacter and Bacillus megaterium isolated from the rhizosphere of wild plants grown on saline–alkaline lands

Salt-induced soil degradation is common in farmlands and limits the growth and development of numerous crop plants in the world. In this study, we isolated salt-tolerant bacteria from the rhizosphere of Tamarix chinensis, Suaeda salsa and Zoysia sinica, which are common wild plants grown on a saline–alkaline land, to test these bacteria's efficiency in alleviating salt stress in tomato plants. We screened out seven strains (TF1–7) that are efficient in reducing salt stress in tomato seedlings. The sequence data of 16S rRNA genes showed that these strains belong to Arthrobacter and Bacillus megaterium. All strains could hydrolyze casein and solubilize phosphate, and showed at least one plant growth promotion (PGP)-related gene, indicating their potential in promoting plant growth. The Arthrobacter strains TF1 and TF7 and the Bacillus megaterium strain TF2 and TF3 could produce indole acetic acid under salt stress, further demonstrating their PGP potential. Tomato seed germination, seedling length, vigor index, and plant fresh and dry weight were enhanced by inoculation of Arthrobacter and B. megaterium strains under salt stress. Our results demonstrated that salt-tolerant bacteria isolated from the rhizosphere of wild plants grown on saline–alkaline lands could be used for alleviating salt stress in crop plants.     

Isolation and Structure Elucidation of a New Antifungal and Antibacterial Antibiotic Produced by Streptomyces sp. 201

An antibacterial and antifungal antibiotic was isolated from the culture filtrate of Streptomyces sp. 201, and its structure was determined as 2-methyl-heptyl isonicotinate by extensive use of NMR spectroscopy. The compound exhibited marked antimicrobial activity against Bacillus subtilis, Shigella sp., Klebsiella sp., E. coli, Proteus mirabilis, and the pathogenic fungi, Fusarium moniliforme, F. semitectum, F. oxysporum, F. solani and Rhizoctonia solani.     

Isolation and structure elucidation of a new antifungal and antibacterial antibiotic produced by Streptomyces sp. 201

An antibacterial and antifungal antibiotic was isolated from the culture filtrate of Streptomyces sp. 201, and its structure was determined as 2-methyl-heptyl isonicotinate by extensive use of NMR spectroscopy. The compound exhibited marked antimicrobial activity against Bacillus subtilis, Shigella sp., Klebsiella sp., E. coli, Proteus mirabilis, and the pathogenic fungi, Fusarium moniliforme, F. semitectum, F. oxysporum, F. solani and Rhizoctonia solani.     

Characterization of PGP Traits of a Hexavalent Chromium Resistant Raoultella sp. Isolated from the Rice Field near Industrial Sewage of Burdwan District,WB, India

Chromium (Cr) is the most toxic at its hexavalent state. Widespread use of chromium for various anthropogenic activities causing rapid decline of the agricultural productivity is now a major global concern. The purpose of this study was to isolate the plant growth promoting (PGP) chromium-resistant bacteria and characterize it before being applied for bioremediation. A potent Cr-resistant rhizobacterium (CrS2) was isolated from the rice field near an industrial sewage and identified as Raoultella sp. based on 16S rDNA sequence homology with some phenotypic characteristics. The strain exhibited Cr(VI) resistance up to 25 mM and also possesses some important PGP traits. The selected CrS2 strain has varied degrees of resistance to other toxic heavy metals/metalloids like arsenic, cadmium, and lead. The removal capacity of chromium was studied in broth cultures. The appropriate growth media for the strain is peptone yeast glucose media with glucose (0.5%) and peptone (1%) as carbon and nitrogen sources, respectively. The strain removed substantial amount of chromium after media optimization. The chromate reductase (EC.1.6.5.2) activity was constitutive in nature of this strain. Thus, the strain CrS2 may be exploited for bioremediation of Cr(VI) in Cr-contaminated agricultural soil, where it might also enhance plant growth promotion.     

The survival of plant growth promoting microorganisms in peat inoculant as measured by selective plate counting and enzyme-linked immunoassay

Achieving specific counting of plant growth promoting (PGP) microorganisms maintained at high numbers in inert carriers such as peat is an important objective for the inoculation of field crops such as cereals. In this paper, methods based on selective media together with strain-specific counting using enzyme-linked immunoassay (ELISA) were examined. Selective plate counting was developed by screening four commercial PGP biofertiliser strains for resistance to antibiotics. ELISAs for each strain were developed and calibrated by purifying polyclonal antibodies, testing sample pre-treatment strategies, and investigating the effect of culture age on standard curves. Selective plate counting proved to be more accurate than the ELISA methodology, confirming that all microbial strains survived for at least 1 month in sterile peat without loss in viable numbers, and further demonstrated growth inhibition of the strain Candida tropicalis HY when co-inoculated with the other strains Pseudomonas fluorescens 1 N, Bacillus amyloliquefaciens E19 and Bacillus subtilis B9. This is the first known study to have investigated the dynamics of PGP microorganisms in multi-strain inoculants and demonstrates the utility and hitherto unmentioned drawbacks of two different low-cost counting methods for biofertiliser quality control. Such information is vital for the adoption and success of non-rhizobial PGP biofertilisers for sustainable agriculture.     

芽孢杆菌SK007的分类鉴定及其拮抗植物病原菌的功能分析

【背景】农业生产中,发掘和利用具有生防功能的微生物资源是保障粮食安全和提高作物产量的重要举措。【目的】明确土壤中芽孢杆菌SK007的分类地位,验证其对多种植物病原菌的拮抗作用,挖掘潜在的生防功能。【方法】通过16SrRNA基因和基因组分析方法确定分离菌株SK007的分类地位;采用平板对峙法研究该菌株对番茄灰霉病菌、白菜黑斑病菌、烟草赤星病菌、小麦赤霉病菌、马铃薯干腐病菌等植物病原菌的拮抗作用;采用AntiSMASH分析和预测菌株SK007的抗生素相关基因。【结果】基于16SrRNA基因、全基因组序列、平均核苷酸一致性和DNA同源性分析,结果表明菌株SK007属于Bacillus velezensis,并且具有产生脂肽类抗生素和聚酮类抗生素的基因,对多种植物病原真菌有较强的抗性。此外,菌株SK007基因组中抗生素基因簇数目较多,丰富度高。【结论】芽孢杆菌SK007在拮抗植物病原菌方面有许多优良性状,具有促进作物抗病和增产的潜力。     

Isolation of lipid- and polysaccharide-degrading micro-organisms from subtropical forest soil, and analysis of lipolytic strain Bacillus sp. CR-179

AIMS: To isolate the micro-organisms from three soil samples obtained from a subtropical forest of Puerto Iguazu (Argentina), to analyse them for detection of the biotechnologically interesting enzymatic activities lipase, esterase, cellulase, xylanase and pectinase, and to identify the most active strain. METHODS AND RESULTS: A total of 724 strains were isolated using different culture media and temperatures, and 449 of them showed at least one of the hydrolytic activities pursued. Lipolytic activity of the lipid-degrading strains was further determined using MUF-butyrate and MUF-oleate as substrates. The alkalophilic strain CR-179, one of the most active for all the enzymatic activities assayed, was characterized and preliminarily identified by morphological, physiological and 16S rDNA tests, as a Bacillus sp. closely related to Bacillus subtilis. CONCLUSIONS: Highly hydrolytic strains were isolated from all soil samples, suggesting the existence of a microbial community well-adapted to nutrient recycling. Strain CR-179, one of the most active, has been preliminarily identified as a Bacillus sp. SIGNIFICANCE AND IMPACT OF THE STUDY: A collection of hydrolytic strains with high biotechnological potential was obtained. Presence of sequences codifying for a lipolytic system related to the B. subtilis group lipases was revealed by PCR for the best lipolytic strain.     

Suppression of maize root diseases caused by Macrophomina phaseolina, Fusarium moniliforme and Fusarium graminearum by plant growth promoting rhizobacteria.

A plant growth-promoting isolate of a fluorescent Pseudomonas sp. EM85 and two bacilli isolates MR-11(2) and MRF, isolated from maize rhizosphere, were found strongly antagonistic to Fusarium moniliforme, Fusarium graminearum and Macrophomina phaseolina, causal agents of foot rots and wilting, collar rots/stalk rots and root rots and wilting, and charcoal rots of maize, respectively. Pseudomonas sp. EM85 produced antifungal antibiotics (Afa+), siderophore (Sid+), HCN (HCN+) and fluorescent pigments (Flu+) besides exhibiting plant growth promoting traits like nitrogen fixation, phosphate solubilization, and production of organic acids and IAA. While MR-11(2) produced siderophore (Sid+), antibiotics (Afa+) and antifungal volatiles (Afv+), MRF exhibited the production of antifungal antibiotics (Afa+) and siderophores (Sid+). Bacillus spp. MRF was also found to produce organic acids and IAA, solubilized tri-calcium phosphate and fixed nitrogen from the atmosphere. All three isolates suppressed the diseases caused by Fusarium moniliforme, Fusarium graminearum and Macrophomina phaseolina in vitro. A Tn5:: lacZ induced isogenic mutant of the fluorescent Pseudomonas EM85, M23, along with the two bacilli were evaluated for in situ disease suppression of maize. Results indicated that combined application of the two bacilli significantly (P = 0.05) reduced the Macrophomina-induced charcoal rots of maize by 56.04%. Treatments with the MRF isolate of Bacillus spp. and Tn5:: lacZ mutant (M23) of fluorescent Pseudomonas sp. EM85 significantly reduced collar rots, root and foot rots, and wilting of maize caused by Fusarium moniliforme and F. graminearum (P = 0.05) compared to all other treatments. All these isolates were found very efficient in colonizing the rhizotic zones of maize after inoculation. Evaluation of the population dynamics of the fluorescent Pseudomonas sp. EM85 using the Tn5:: lacZ marker and of the Bacillus spp. MRF and MR-11(2) using an antibiotic resistance marker revealed that all the three isolates could proliferate successfully in the rhizosphere, rhizoplane and endorhizosphere of maize, both at 30 and 60 days after seeding. Four antifungal compounds from fluorescent Pseudomonas sp. EM85, one from Bacillus sp. MR-11(2) and three from Bacillus sp. MRF were isolated, purified and tested in vitro and in thin layer chromatography bioassays. All these compounds inhibited R. solani, M. phaseolina, F. moniliforme, F. graminearum and F. solani strongly. Results indicated that antifungal antibiotics and/or fluorescent pigment of fluorescent Pseudomonas sp. EM85, and antifungal antibiotics of the bacilli along with the successful colonization of all the isolates might be involved in the biological suppression of the maize root diseases.