Plant growth-promoting properties and anti-fungal activity of endophytic bacterial strains isolated from Thymus altaicus and Salvia deserta in arid lands

Endophytes,as crucial components of plant microbial communities,significantly contribute to enhancing the absorption of nutrients such as nitrogen and phosphorus by their hosts,promote plant growth,and degrade pathogenic fungal mycelia.In this study,an experiment was conducted in August 2022 to explore the growth-promoting potential of endophytic bacterial strains isolated from two medical plant species,Thymus altaicus and Salvia deserta,using a series of screening media.Plant samples of Thymus altaicus and Salvia deserta were collected from Zhaosu County and Habahe County in Xinjiang Uygur Autonomous Region,China,in July 2021.Additionally,the inhibitory effects of endophytic bacterial strains on the four pathogenic fungi(Fusarium oxysporum,Fulvia fulva,Alternaria solani,and Valsa mali)were determined through the plate confrontation method.A total of 80 endophytic bacterial strains were isolated from Thymus altaicus,while a total of 60 endophytic bacterial strains were isolated from Salvia deserta.The endophytic bacterial strains from both Thymus altaicus and Salvia deserta exhibited plant growth-promoting properties.Specifically,the strains of Bacillus sp.TR002,Bacillus sp.TR005,Microbacterium sp.TSB5,and Rhodococcus sp.TR013 demonstrated strong cellulase-producing activity,siderophore-producing activity,phosphate solubilization activity,and nitrogen-fixing activity,respectively.Out of 140 endophytic bacterial strains isolated from Thymus altaicus and Salvia deserta,104 strains displayed anti-fungal activity against Fulvia fulva,Alternaria solani,Fusarium oxysporum,and Valsa mali.Furthermore,the strains of Bacillus sp.TR005,Bacillus sp.TS003,and Bacillus sp.TSB7 exhibited robust inhibition rates against all the four pathogenic fungi.In conclusion,the endophytic bacterial strains from Thymus altaicus and Salvia deserta possess both plant growth-promoting and anti-fungal properties,making them promising candidates for future development as growth-promoting agents and biocontrol tools for plant diseases.

Application Progress of Plant Growth-promoting Bacteria in Crops

Plant growth-promoting bacteria(PGPBs)can promote plant growth and improve crop yield.They can induce plant systemic resistance to resist biotic and abiotic stresses.In recent years,with the development of green ecological agriculture,new biological fertilizers such as microbial inocula and microbial fertilizers based on PGPBs have been gradually applied in crop planting.Based on plant growth promotion and disease control,the application progress of PGPBs in crops from the aspects of growth promotion mechanism,growth promotion effect,resistance to biological and abiotic stresses were discussed,aiming to provide reference for the relevant research and application of PGPBs in crops.

Effect of Inoculation with Three Phytohormone Producers Phytobacteria with ACC Deaminase Activity on Root Length of Lens esculenta Seedlings

Plant-associated bacteria that inhabit the rhizosphere may influence the plant growth by their contribution to the endogenous pool of phytohormones and by the activity of ACC deaminase to decrease the ethylene concentration. The aim of this study was to analyse the root length growth by the promoting effect of indole acetic acid producers phytobacteria with ACC deaminase activity, on inoculated seeds of Lens esculenta as synergistic effect on root elongation. In this study, although the roots of L. esculenta seedlings do not show a significant promotion, these phytobacteria could be recommended to treat plants analyzing their added inoculum to increase plant biomass and retard the effect of ethylene on cultures supplied with Tryptophan and ACC.

多功能根际生防促生放线菌的分离鉴定及其对辣椒的益生效果

从健康辣椒根际土壤筛选具防病促生功能的菌种并应用于生物障碍土壤,可为辣椒提质增产和根腐病的防治提供优质的菌剂资源。本研究以辣椒根腐病的病原菌——腐皮镰孢菌(Fusarium solani)为靶标菌,采用平板对峙法筛选优良生防菌株,对其固氮、溶磷、解钾、分泌3-吲哚乙酸(3-indole acetic acid,IAA)、产铁载体、产纤维素酶和蛋白酶、利用酚酸类连作障碍物质等能力进行定性和定量测定。采用形态学、生理生化及16S rRNA基因序列对分离菌株进行鉴定,并采用田间原位栽培试验检测其生防和促生效果。结果表明,从设施连作抗病辣椒根际土中获得6株具有抑菌作用的放线菌,通过定性、定量测试发现菌株G-1拮抗效果最强,其对设施蔬菜5种常见病原菌均具有较好的抑制效果,抗菌谱广,且具有分泌IAA、产铁载体、产纤维素酶和蛋白酶、溶解有机磷、利用酚酸类化感物质等特性。结合形态学、生理生化及16S rRNA进化树分析结果,将其鉴定为弗氏链霉菌(Streptomyces fradiae)。田间原位栽培试验显示,G-1菌剂对辣椒根腐病具有较好的防病作用,可显著降低根腐病的病情指数,促进辣椒根系生长,且可使辣椒增产31.04%。研究表明,弗氏链霉菌G-1具有优良的防病促生功能,其固体菌剂的田间应用对辣椒根腐病具有较好的防治效果,且对辣椒具有明显的促生增产作用,可作为辣椒益生菌剂的候选菌株资源。

红树林湿地植物生长促进菌及其应用展望

着重介绍从红树林根系中提取的植物促生菌的种类,即固氮细菌、溶磷细菌、光合厌氧细菌及其在红树林植被恢复中的应用前景。

植物促生菌在农作物上的应用进展(综述)

植物促生菌(PGPB)能够促进植物生长、提高作物产量,具有诱导植物产生系统抗性来抵御生物和非生物胁迫的作用。近年来,随着绿色生态农业的发展,以促生菌为主的微生物菌剂、菌肥等新型生物肥料逐渐应用于农作物种植。基于植物促生和病害防治2个方面,从促生机理、促生效果、抵御生物和非生物胁迫等方面对PGPB在农作物上的应用进展进行了论述,以期为PGPB在农作物上的相关研究和应用提供参考。

Selection and validation of reference genes for quantitative real-time polymerase chain reaction analyses of Serratia ureilytica DW2

Background:Serratia ureilytica DW2 is a highly efficient phosphate-solubilizing bacteria isolated from Codonopsis pilosula rhizosphere soil that can promote the growth of C.pilosula;nonetheless,until now,no validated reference genes from the genus Serratia have been reported that can be used for the normalization of quantitative real-time polymerase chain reaction(RT–qPCR)data.Methods:To screen stable reference genes of S.ureilytica DW2,the expression of its eight candidate reference genes(16S rRNA,ftsZ,ftsA,mreB,recA,slyD,thiC,and zipA)under different treatment conditions(pH,temperature,culture time,and salt content)was assayed by RT–qPCR.The expression stability of these genes was analyzed using different algorithms(geNorm,NormFinder,and BestKeeper).To verify the reliability of the data,the expression of the glucose dehydrogenase(gdh)gene under different soluble phosphate levels was quantified using the most stably expressed reference gene.Results:The results showed that the zipA and 16S rRNA genes were the most stable reference genes,and the least stable genes were thiC and recA.The expression of gdh was consistent with the phosphate solubilization ability on plates containing the National Botanical Research Institute phosphate growth medium.Conclusion:Therefore,this study provides a stable and reliable reference gene of Serratia for the accurate quantification of functional gene expression in future studies.

胡杨根际细菌提高木本植物对重金属胁迫的耐受性

胡杨是我国西北荒漠地区特有的、对多种非生物逆境具有高抗逆性的树种,但其相关微生物的生态和生理功能研究还比较缺乏.本文从新疆沙雅地区原始胡杨林根际土壤中分离出重金属抗性细菌共72株.其中具有单一重金属(Cu2+、Ni2+、Pb2+或Zn2+)抗性的细菌菌株50株,有三重以上重金属抗性的菌株9株.将其中5株多重重金属抗性细菌接种至生根的竹柳插条,进行重金属胁迫下的盆栽培养.结果表明:在铜或锌胁迫下,5株多重重金属抗性细菌对竹柳的生长抑制有不同程度的缓解,其中假单胞菌Z30和贪铜菌N8菌对铜和锌两种胁迫下竹柳生物量的增长与不接菌对照相比均达到显著差异水平.说明在非重金属污染区生长的胡杨根际存在多样性的重金属抗性细菌,其中一些多重重金属抗性菌对改善重金属胁迫下植物的生长有显著作用,具有应用于木本植物-微生物联合修复环境重金属污染的价值.

植物促生菌在重金属生物修复中的作用机制及应用

重金属污染是导致生态和环境退化的主要因素之一.土壤重金属污染会降低土壤质量、农作物产量和品质,甚至威胁人类健康.因此,优化土壤重金属污染治理措施,对于农业高产优质可持续具有重要意义.诸多国内外学者在重金属污染植物修复方面开展了大量研究,但由于受土壤和气候环境条件的影响,其修复效率受到制约.微生物与植物的协同修复被认为是环境胁迫条件下提高重金属污染修复效率的一种有效手段.耐重金属的植物促生细菌(PGPB)不仅可以促进植物生长,提高对生物胁迫(如病原菌)和非生物胁迫(如干旱、高盐、极端温度和重金属等)的抗性,还可以改变土壤中重金属的生物利用度和毒性,从而提高植物对重金属的修复效率.系统地梳理了耐重金属的PGPB在促进植物生长,增强植物抗逆性和影响重金属生物利用度方面的作用机制,并进一步综述了近年来国内外关于PGPB在生态修复中的应用和研究进展.

Isolation,Identification,and Characterization of an Aluminum-Tolerant Bacterium Burkholderia sp.SB1 from an Acidic Red Soil

Aluminum(Al) toxicity usually occurs in acidic soils worldwide, which is detrimental to the growth of organisms. An Al-tolerant bacterium, SB1, was isolated from an acidic red soil of Chingkang Mountain, located in Jiangxi Province of China. Polyphasic analysis,including a 16 S rDNA phylogenetic tree as well as morphological and physicochemical properties, revealed that the isolate was a gramnegative, rod-shaped bacterium, which was recognized as Burkholderia sp. SB1 and had extreme acidity tolerance(pH 2.2) and excellent Al resistance(270 mg L^(-1) Al^(3+)). It could remove Al by up to 97.7% at a concentration of 54 mg L^(-1) Al^(3+). SB1 behavior under different temperatures and antibiotics was also examined. SB1 preferred moderate temperature conditions, ranging from 25 to37?C, and exhibited notable resistance to multiple antibiotics(including ampicillin, streptomycin, and tetracycline), except for being sensitive to chloramphenicol. Therefore, as the first reported bacterium to possess favorable Al resistance and excellent Al removal,Burkholderia sp. SB1 can potentially be used as an agent for bioremediation of Al-contaminated acidic red soils.

重金属固定植物促生细菌的筛选及其阻控小麦富集重金属效应

由于工业和采矿业等人类的活动造成农田土壤Cd和Pb污染日益严重,并可通过食物链严重影响人类健康,必须采取有效措施阻控农作物对重金属的吸收.本研究依据细菌的重金属抗性和植物促生特性筛选功能菌株,并通过摇瓶吸附实验和小麦砂培实验验证其对小麦生长和阻控小麦吸收Cd和Pb的影响.结果显示,从狗尾草根际土壤中共分离到具有固定重金属和促生能力的菌株18株,其中巨大芽孢杆菌N3和液质沙雷氏菌H12效果最好,均能抵抗高质量浓度的Cd(650mg·L^-1)和Pb(2 700 mg·L^-1),分泌吲哚乙酸(IAA)(56.6 mg·L^-1和69.1 mg·L^-1)、铁载体和1-氨基环丙烷羧酸(ACC)脱氨酶.静置培养实验表明,菌株N3和H12显著提高溶液中NH4+的质量浓度和p H值,降低溶液中Cd(63.1%~73.8%)和Pb(69.1%~81.8%)的质量浓度.砂培条件下,与不接菌相比,菌株N3和H12不仅能够显著增加小麦根(47.2%~97.4%)和地上部(65.3%~153%)的干重,还能够显著降低小麦根和地上部中Cd(49.2%~68.3%)和Pb(27.4%~84.5%)的含量.本研究结果为Cd、Pb污染农田的修复和农作物的安全生产提供菌种资源和理论依据.

Drought-Tolerant Pseudomonas spp. Improve the Growth Performance of Finger Millet(Eleusine coracana(L.) Gaertn.)Under Non-Stressed and Drought-Stressed Conditions

Application of plant growth-promoting bacteria(PGPB)is an environmentally sustainable option to reduce the effects of abiotic and biotic stresses on plant growth and productivity.Three 1-aminocyclopropane-1-carboxylic acid(ACC)deaminase-producing drought-tolerant bacteria were isolated from a rain-fed agriculture field in the Central Himalaya of Kumaun region,Uttarakhand,India and evaluated for their efficiency in improving finger millet(Eleusine coracana(L.)Gaertn.)plant growth under non-stressed and drought-stressed conditions.These bacteria withstood a substrate metric potential of -1.0 MPa(30% polyethylene glycol 8000)and therefore were considered drought-tolerant.These strains were identified as Pseudomonas spp.by fatty acid methyl ester analysis and 16S rRNA gene sequencing.The ACC deaminase activity of these strains was characterized at the biochemical level,and the presence of acd S gene,the structural gene for ACC deaminase,was confirmed by the polymerase chain reaction.Two sets of pot trials in glass house were set up,one for normal(non-stressed)and the other for drought-stressed conditions.After 5 weeks,one set of plants was subjected to drought stress for 5 d,while the other set continued to be watered.The same growth parameters were recorded for both sets of plants after 40 d of plant growth.The results of pot trials showed that treatments inoculated with ACC deaminase-producing bacterial strains significantly improved the growth performance of finger millet plants and foliar nutrient content as compared to uninoculated treatments under both non-stressed and drought-stressed conditions.In addition,a significant increase in antioxidant activity was observed,wherein bacterial stain inoculation improved plant fitness by protecting it from oxidative damage induced by drought.

Biosurfactant-assisted phytoremediation of potentially toxic elements in soil:Green technology for meeting the United Nations Sustainable Development Goals

Biosurfactants are biomolecules produced by microorganisms, low in toxicity, biodegradable, and relatively easy to synthesize using renewable waste substrates. Biosurfactants are of great importance with a wide and versatile range of applications, including the bioremediation of contaminated sites. Plants may accumulate soil potentially toxic elements(PTEs), and the accumulation efficacy may be further enhanced by the biosurfactants produced by rhizospheric microorganisms. Occasionally, the growth of bacteria slows down in adverse conditions, such as highly contaminated soils with PTEs. In this context,the plant's phytoextraction capacity could be improved by the addition of metal-tolerant bacteria that produce biosurfactants. Several sources, categories,and bioavailability of PTEs in soil are reported in this article, with the focus on the cost-effective and sustainable soil remediation technologies, where biosurfactants are used as a remediation method. How rhizobacterial biosurfactants can improve PTE recovery capabilities of plants is discussed, and the molecular mechanisms in bacterial genomes that support the production of important biosurfactants are listed. The status and cost of commercial biosurfactant production in the international market are also presented.

Agronomic evaluation of Herbaspirillum seropedicae strain ZAE94 as an inoculant to improve maize yield in Brazil

Diazotrophic bacteria applied as a seed inoculant can improve the grain yield of several crops including maize. The current study aimed to test the agronomic efficiency and contribution of biological nitrogen fixation(BNF) of the endophytic diazotroph Herbaspirillum seropedicae strain ZAE94 to maize under field conditions. Eighteen field assays were conducted in four different locations during consecutive years on two hybrids and two varieties of maize in a random block design with four replicates using a peat-based inoculant. The inoculant containing the ZAE94 strain was applied without nitrogen(N)fertilization or with 40 kg N ha^(-1) and was compared to the application of 40 and 80 kg N ha^(-1) without inoculation. Crop productivity and N accumulation in the grain were evaluated in addition to ^(15)N natural abundance(δ^(15)N) to evaluate BNF in the treatments without N fertilization. Fertilization at 40 kg N ha^(-1) plus bacterial inoculation produced crop yields similar to the treatment with 80 kg N ha^(-1) and increased grain N content, especially in the off-season with 40 kg N ha^(-1). The inoculation treatments showed lower δ^(15)N values than the non-inoculated treatments, which was most evident in the off-season. The BNF contributed about 30% of N accumulated in plants inoculated with ZAE94. On average, 64% of the N fertilized plots showed an increase of the parameters evaluated in the inoculated treatments, compared with the control. Inoculation also increased root length, root volume, and leaf area, and these parameters were positively correlated with plant weight using a hydroponic assay. This study revealed that the application of H. seropedicae inoculant increased the amount of N in plants owing to BNF, and there is a better chance of yield response to inoculation under low N fertilizer application in the off-season.

Co-inoculation of indigenous Pseudomonas oryzihabitans and Bradyrhizobium sp.modulates the growth,symbiotic efficacy,nutrient acquisition,and grain yield of soybean

Soil microbes play a vital role in improving plant growth,crop productivity,and soil health through solubilization of essential nutrients.Present investigation was conducted to access the efficacy of Bradyrhizobium sp.LSBR-3 and the indigenous phosphate-solubilizing Pseudomonas oryzihabitans LSE-3 in improving the symbiosis,nutrient accumulation,and yield of soybean.The isolate LSE-3,selected on the basis of phosphate solubilization,was screened for beneficial traits,antagonistic activities,and pathogenicity.The levels of indole acetic acid production(50.34±2.35μg mL^(-1)),phosphate solubilization(184.4±7.4 mg L^(-1)),biofilm formation(optical density at 560 mm,1.3896±0.04),siderophore production(121.46±1.61μg mL^(-1)),and 1-aminocyclopropane-1-carboxylate deaminase activity(0.51±0.07 mmolα-ketobutyrateμg^(-1) protein h^(-1))were significantly higher with the dual inoculants(LSBR-3 and LSE-3)than with the single inoculant LSBR-3.The plant growth-promoting traits of single and dual inoculants were evaluated for the synergistic effects on soybean under field conditions.Soybean plots treated with LSBR-3+LSE-3 exhibited improvement in seed germination,plant height,plant biomass,and chlorophyll content compared with the uninoculated control.Dual inoculant treatments resulted in significantly higher symbiotic efficacy evidenced by increased nodulation(40.0±0.75 plant^(-1)),nodule biomass(188.52±6.29 mg plant^(-1)),and leghemoglobin content(11.02±0.83 mg g^(-1) fresh nodule),and significantly increased activities of phosphatase(75.16±3.17 and 58.77±6.08μg p-nitrophenol g^(-1) h^(-1) for alkaline and acid phosphatase,respectively)and dehydrogenase(32.66±1.92μg triphenylformazan g^(-1) h^(-1))compared with the control.Dual inoculation with LSBR-3 and LSE-3 enhanced the uptake of macro-and micronutrients,reduced Na content in shoots,and resulted in 10.85%higher grain yield and ca.US$96.80 ha^(-1) higher profit compared with the control.This is the first report on the effectiveness of combined inoculation of LSE-3 and LSBR-3 in promoting the growth,symbiotic efficacy,and yield of soybean for sustainable agriculture.

一株李维斯链霉菌的鉴定及其抗病促生性能

【目的】探究一株李维斯链霉菌的抗病促生性能,鉴定其抑菌活性成分。【方法】从耐旱稗草根际分离到一株能抑制多种病原真菌及细菌的链霉菌,采用形态学观察及16SrRNA基因序列分析的方法对菌株进行鉴定;运用液相色谱和高分辨质谱技术鉴定活性物质成分;利用二代Illumina与三代Nanopore测序技术进行全基因组测序;antiSMASH分析该菌株中活性成分的生物合成基因簇。【结果】李维斯链霉菌L2的菌体及发酵液能高效抑制革兰氏阳性菌及多种植物病原真菌的生长,能在铬天青平板(chrome azurol sulphonate,CAS)上产生较大的噬铁圈,还具有较好的产吲哚乙酸(indole-3-acetic acid,IAA)的能力。其抑菌活性成分的m/z为537.1020[M+H]^(+)(calcd for C_(27)H_(20)O_(12),537.1035,2.2×10^(-6)),523.0863[M+H]^(+)(calcd for C_(26)H_(18)O_(12),523.0878,2.9×10^(-6)),分别与α-鲁霉素、β-鲁霉素、γ-鲁霉素的精确分子量相符,误差小于1/5000000,其高效液相色谱保留时间与鲁霉素标准品一致。该菌基因组总长8.8 Mb,预测编码有鲁霉素等32个次级代谢产物生物合成基因簇。【结论】李维斯链霉菌L2具有较好的抗病促生性能,适宜进一步开发为生防菌剂,其抑菌活性成分为鲁霉素。