Effects of Inoculation with Phosphate Solubilizing Bacteria on the Physiology,Biochemistry,and Expression of Genes Related to the Protective Enzyme System of Fritillaria taipaiensis P.Y.Li

Fritillaria taipaiensis P.Y.Li is a widely used medicinal herb in treating pulmonary diseases.In recent years,its wild resources have become scarce,and the demand for efficient artificial cultivation has significantly increased.This article is the first to apply phosphate solubilizing bacteria isolated from the rhizosphere soil of F.taipaiensis P.Y.Li to the cultivation process of F.taipaiensis P.Y.Li.The aim is to identify suitable reference strains for the artificial cultivation and industrial development of F.taipaiensis P.Y.Li by examining the effects of various phosphate solubilizing bacteria and their combinations on photosynthesis,physiological and biochemical properties,and gene expression related to the protective enzyme system in F.taipaiensis P.Y.Li.The experiment,conducted in pots at room temperature,included a control group(CK)and groups inoculated with inorganic phosphorussolubilizing bacteria:W1(Bacillus cereus),W2(Serratia plymuthica),W12(Bacillus cereus and Serratia plymuthica),and groups inoculated with organophosphorus-solubilizing bacteria:Y1(Bacillus cereus),Y2(Bacillus cereus),Y12(Bacillus cereus and Bacillus cereus),totaling seven groups.Compared to CK,most growth indices in the bacterial addition groups showed significant differences,with W12 achieving the highest values in all indices except the leaf area index.The content of photosynthetic pigments,photosynthetic parameters,and osmoregulatory substances increased variably in each bacterial treatment group.W12 exhibited the highest content of chlorophyll a and soluble protein,while W1 had the highest free proline content.The activities of peroxidase(POD),superoxide dismutase(SOD),and catalase(CAT)in all inoculated groups were higher than in CK,with significant changes in SOD and CAT activities.The malondialdehyde(MDA)content in all inoculated groups was lower than in CK,with Y12 being the lowest,at approximately 30%of CK.Gene expression corresponding to these three enzymes also increased variably,with POD expression in Y2 being the highest at 2.73 times that of CK.SOD and CAT expression in Y12 were the highest,at 1.84 and 4.39 times that of CK,respectively.These results indicate that inoculating phosphate solubilizing bacteria can enhance the growth of F.taipaiensis P.Y.Li,with the mixed inoculation groups W12 and Y12 demonstrating superior effects.This lays a theoretical foundation for selecting bacterial fertilizers in the cultivation process of F.taipaiensis P.Y.Li.

Amelioration of Salt Stress on Wheat Plants Growth in Coastal Saline Soil by a Phosphate Solubilizing Bacterium Enterobacteria sp. EnHy-401

A pot experiment was conducted to examine the effects of a phosphate solubilizing bacterium（PSB）,Enterobacteria sp.EnHy-401,on the availability of insoluble accumulative phosphorus（P）and growth of wheat（Triticum Ningmai No.13）plants in sterile saline soil.Our results showed that the strain EnHy-401 had the ability to activate the insoluble accumulated phosphorus in saline soil and enhanced nutrient uptake efficiency by wheat plants,then conferred resistance in wheat plants to salt stress and resulted in a significant growth increase.In saline soil inoculated with Enterobacteria sp.EnHy-401,available phosphorus and exchangeable calcium was increased from 6.4 mg/kg and 1 162 mg/kg to 10.3 mg/kg and 1 214 mg/kg,respectively.Wheat seedling grown in soil inoculated with the EnHy-401 strain increased shoot weight by 28.1% and root weight by 14.6% when compared to the control.P,Ca,K and Mg contents in shoots increased 34.4%,36.3%,31.5%,and 6.3% compared to the control,respectively.the fact that the increases in available P,biomass P,and Ca2＋ concentration in saline soil treated with PSB Enterobacter sp.EnHy-401 inocula,and high relativity between the P,Ca,K,and Mg content in wheat tissue and dry matter indicated that PSB Enterobacter sp.EnHy-401 suppressed the adverse effect of salinity stress in plants through nutrient（P and Ca）supply and nutrient（K and Mg）uptake enhancement.The phosphate solubilizing activity of Enterobacteria sp.EnHy-401 and the amelioration of salt stress on wheat plants by the strain varied with the salinity levels and content of organic matter in the saline soil.

Assessment of biotechnological potential of phosphate solubilizing bacteria isolated from soils of Southern Kazakhstan

Phosphorus (P) is a vital plant nutrient, available to plant roots only in soluble forms that are in short supply in the soil. Adding phosphate- based fertilizers to increase agricultural yields is a widely used practice;however, the bio- availability of P remains low due to chemical transformations of P into insoluble forms. Thus, phosphate solubilizing bacteria (PSB) play an important role in reducing P deficiency in soil. The goal of this study was to assess biotechnological potential of phosphate-solubilizing bacterial strains. In this study, phosphate solubilizing microorganisms (PSM) were isolated from different soil samples of Southern regions of Kazakhstan. The biological activity of PSM was studied based on their effect on the growth of wheat seeds. The different taxonomic genera of these PSM were identified: Arthrobacter spp., Aureobacterium spp., Azotobacter spp., Bacterium spp., Baccillus spp. Finally, phosphate- solubilizing activity of isolated strains of PSM was assessed.

Phosphorus Solubilizing Capability,IAA Secretion and Characteristics of Phosphorus-solubilizing Bacteria in Rhizosphere of Alfalfa in Guizhou Province

[Objective] The study aimed to isolate and screen efficient phosphorus-sol- ubilizing strains from the root soil of alfalfa in Guizhou, and investigate its growth promoting mechanism. [Method] Phosphorus solubilizing bacteria were isolated from rhizosphere of alfalfa with inorganic and organic phosphorous medium and the strains with higher capacity of dissolving phosphorus were screened through dissolv- ing phosphate zone and further researched. Meanwhile the phosphorus solubilizing capability of strains cultured in liquid medium was investigated by molybdenum blue colorimetric method. [Result] The capacity of dissolving calcium phosphate of 11 se- lected strains differed significantly and tended to be volatile from 150.40 to 268.20 μg/ml; phosphate solubilization capacity, IAA secretion and the pH of culture media did not show any significant correlation; all strains could produce IAA, and the se- cretion was from 12.09 to 22.16 μg/ml; the selected strains all could produce alka- line matter, and most of colonies were pale or milky white, irregular, opaque, jagged, flat and non-pigmented; utilization of carbon sources by different strains varied signifi- cantly. [Conclusion] The study laid the foundation for relieving phosphorus in unpro- ductive land, saving phosphate resources, reducing environmental pollution and pro- viding fertilizer in alfalfa production.

A Feasible Way of Degrading Malathion Pesticide under Laboratory Condition Using Phosphate Solubilizing Bacteria

An experiment was carried out for identification and determination of malathion degrading phosphate solubilizing bacteria isolated from the agricultural fields. In this study, malathion degrading phosphate solubilizing bacteria were identified using NBRIP (National Botanical Research Institute’s phosphate growth medium) media. A number of bacterial colonies were screened from agricultural fields. From primarily screened colonies 4 isolates were identified as phosphate solubilizing bacteria through qualitative and quantitative analysis. The isolated 4 bacterial colonies were inoculated in NBRIP broth media enriched with malathion pesticides to observe degradation of malathion pesticide under incubation study at three different temperatures (25°C, 30°C and 37°C). However, all the four isolates showed capability in degrading malathion pesticide. The study clearly revealed that phosphate solubilizing bacteria can be used in bioremediation of environmental pollution caused by malathion pesticide.

Isolation of Six Phosphate Dissolving Rhizosphere Bacteria （Bacillus subtilis） and Their Effects on the Growth, Phosphorus Nutrition and Yield of Maize （Zea mays L.） in Mali

The disadvantages of the long term application of Tilemsi natural phosphate （TNP） on maize （Zea mays L.） production has come out because of its low P availability. Some functional soil microbes, such as phosphate dissolving bacteria, have great potential in improvement of P solubility from TNP and P uptake by plants. The present study aimed to isolate and characterize typical phosphate dissolving bacterial strains （Bacillus subtilis） from Malian soils, and investigate their role in P uptake by maize grown in soils amended with TNP. The experimental design was a split plot with three main plots of fertilizers sources, i.e., natural phosphate, commercial fertilizer and without fertilizer, and with seven sub-plots of six microorganisms plus the control. The field experiment results have shown that the maize inoculated with the phosphate dissolving bacteria was improved in seed germination, plant growth, plant production （increase yield by 42%）, grain and aerial dry biomass （P） content of 34% and 64%, respectively. They have also shown that the locally available TNP can be used by the Malians farmers in maize culture and have comparable production to the one obtained with the costly imported commercial phosphate fertilizer, like the complex cereal. The project has provided information for the combined use of the Mali TNP and phosphate dissolving bacteria Bacillus subtilis subsp, subtilis （T）： DSM 10 in improvement of maize production in the country.

The Ability of Phosphate Solubilizing Bacteria Isolated from Coffee Plant Rhizosphere and Their Effects on Robusta Coffee Seedlings

Phosphate solubilizing bacteria isolated from rhizosphere of coffee plants may play an important role in improving phosphate availability for the plants. However, one of the factors influencing the degree of phosphate solubilization by these bacteria is the ability of the microorganisms to utilize phosphate. The objective of this study was to determine the ability of phosphate solubilizing bacteria isolated from coffee plant rhizosphere and their effects on robusta coffee seedling growth. This research was carried out by taking soil samples from Andungsari （Bondowoso District） and Kaliwining （Jember District） coffee plantations, both located in East Java. Liquid medium of Pikovskaya was used for isolation of phosphate solubilizing bacteria from the soil samples. Results of this study showed that 12 phosphate solubilizing bacteria were obtained from this isolation, eight isolates from Andungsari and four isolates from Kaliwining. Selection of those bacteria isolates was based on the qualitative ability in phosphate solubilizing by measuring the clear zone surrounding the colonies and quantitatively by measuring the solubilized phosphate using spectrophotometer. The results showed that four isolates, in the order of PFpKW1, PFpC61, PFsC62a, and PFsB 11, had the highest qualitative ability in solubilizing phosphate, while for the highest quantitative ability the order was PFpKW 1, PFpC61, PFsC62a, and PFsB 11. In a green house study, inoculation of these selected isolates onto Robusta coffee seedlings positively enhanced the coffee seedling growth. Phenotypic test indicated that the four isolates are similar to the genus of Pseudomonas.

Growth Characteristics of Mixed Bacteria and Its Solubilizing Effect on Low-grade Phosphate Rock

In this paper, the growth characteristics of Acidithiobacillus ferrooxidans （At.f） and Acidithiobacillus thiooxidans （At. f） in mixed culture has been studied, explored mixed bacteria phosphate solubilization effect, from a kind of low-grade phosphate rock. The results show that mixed bacteria has strong ability to produce acid, and have stronger oxidation activity to energy source -Fe^2＋. Mixed bacteria can significantly increase the rate of phosphate solubilization from phosphate rock in low concentration pulp. It goes against mixed bacteria reproduction when pulp concentration increased, makes phosphate solubilization rate decreased.

The Research on Phosphate Mobilizing Bacteria from Soils of Southern Ukraine

Dissemination of phosphate mobilizing bacteria in rhizosphere of winter wheat for soils of Ukrainian South （southern chernosem and dark-chestnut soil） has been studied. The isolation of strains has been cultured in the selective glucose-asparagine medium with Ca3（PO4）2 or phytin. The selection of effective strains of phosphate mobilizing bacteria （PMB） was implemented in several stages. The effective strain of bacteria, conductive to the internalization of bard-soluble organic （phytin） phosphate by plants, has been desorbed from the southern chemozem, its properties have been studied, and its identification has been carried out. The biopreparation phosphoenterin has been composed on the basis of this strain. Phosphoenterin have been widely adopted in the cultivation of winter wheat, barley, vegetables （cabbage, tomato） in southern part and other climatic area of Ukraine.

Selection of Cocoa Tree (<i>Theobroma cacao</i>Linn) Endophytic Bacteria Solubilizing Tri-Calcium Phosphate, Isolated from Seedlings Grown on Soils of Six Producing Regions of C&ocirc;te d’Ivoire

Phosphorus (P) is an essential macronutrient for the growth and development of cocoa tree (Theobroma cacao Linn). Most of the soils used for cocoa farming in C?te d’Ivoire are low in phosphorus. But cocoa farmers generally have a widespread reluctance to invest in chemicals fertilizers due to high costs and environmental associated risk. Phosphate Solubilizing Bacteria (PSB) are kwon to play an important role in supply of phosphorous to plants in a sustainable manner in P deficient soils. The aim of this research was to screen the endophytic bacteria of cocoa nurseries able to solubilize tri-calcium phosphate. Seedlings of two varieties of cocoa (P7 and NA32) and seedlings of an all-comer, were grown on eighteen (18) samples soils collected in six producing regions of C?te d’Ivoire. A total of 218 endophytic bacteria were isolated and tested on the Pikovskaya’s agar medium, containing Ca3 (PO4) 2. The colonies with clear zone around the microbial growth were suspected as phosphate solubilizing bacteria. Out of 218 bacteria, 90 (41.28%) showed a clear zone around colonies after 7 days of incubation. The Phosphate Solubilization Index (PSI) ranged from 20% to 200%. Bacterial isolated from the soils of Duékoué locality showed the highest mean index of 137.67%. Five PSB (CEBSP5, CEBSP6, CEBSP7, CEBSP8, and CEBSP9) from Duékoué soils and two PSB (CEBSP12 and CEBSP13) from Soubré soils have a PSI ranged from 150% to 200%. Further study in greenhouse and in field condition will confirm the use of these PSB as biofertilizer to increase the available P content in soils, reduce environmental pollution and promote sustainable agriculture.

Response of Microbial Community to Petroleum Stress and Phosphate Dosage in Sediments of Jiaozhou Bay, China

The dynamic microcosms were used to evaluate the effect of oil spills on microbial ecological system in marine sediment and the enhancement of nutrient on the oil removal. The function and structure of microbial community caused by the oil pollution and phosphate dosage were simultaneously monitored by dehydrogenase activity assay and PCR-denaturing gradient gel electrophoresis(DGGE) techniques. The results indicated that the amount of total bacteria in all dynamic microcosms declined rapidly with incubation time. The number of petroleum-degrading bacteria and the activity of sediment dehydrogenase were gradually enhanced by petroleum in the oil-treated microcosms, while they both showed no obvious response to phosphate dosage. In comparison, phosphate spiked heterotrophic bacteria and they showed a significant increase in amount. DGGE profiles indicated that petroleum dosage greatly changed community structure, and the bacteria belonged to class Deltaproteobacteria, and phyla Bacteroidetes and Chlorobi were enriched. This study demonstrated that petroleum input greatly impacted the microbial community structure and consequently the marine sediment petroleum-degrading activity was enhanced. Phosphate dosage would multiply heterotrophic bacteria but not significantly enhance the petroleum degradation.

Production of Phosphate-Rich Biofertiliser Using Vermicompost and Anaerobic Digestor Sludge—A Case Study

This paper presents the technology and cost effectiveness of production of phosphate rich biofertiliser (called PROM) by bioconversion of phosphate rock ore into soluble phosphates (that are directly assimilable by plants) in presence of an organic manure such as Vermicompost or anaerobic digestor sludge (discharged from biogas manufacturing units) and using a microbial culture of Bacillus megatherium var phosphaticum. PROM has been found to be an excellent, less expensive, substitute to synthetic phosphatic fertilisers such as SSP, MAP and DAP. This is based on real—life field trials. It is also possible to integrate the production of PROM, with biogas generation and the layout of such a more profitable, integrated scheme is also presented in this paper.

Phosphate solubilization potential of native rhizospheric microflora and their impact on growth of Madhuca latifolia(Mahua):An oil yielding medicinal plant of India

Madhuca latifolia is an economically important medicinal and oil yielding plant of India having slow growth rate.As microbial application to the rhizosphere of host plant are beneficial for growth and development of plants,a comprehensive experimental study by using native microflora of Madhuca latifolia had been carried out in the nursery conditions.Isolation and identification of native rhizospheric soil revealed the occurrence of 17 different types of bacteria(gram negative and positive)and 30 numbers of fungi belonging to myceloid type,Aspergillus,Alternaria,Colletotrichum,Fusarium and Penicillium.Present study was confined to phosphate solubilizing microbes for which solubilization potential(solubilization index and solubilization efficiency)was evaluated.Inoculation experiments in pot culture with red laterite soil were set in two experimental categories(1)non-transplanted and(2)transplanted.Plants grown under both the conditions with and without microbial application were maintained up to 120 days and final data recorded for morphological,physiological growth and as soil parameters.The mineral solubilizing potential of native microbial strains has been expressed.Fungal inoculants were more effective than the bacterial inoculants as far as the growth and development of plants concerned.Among all,bacteria MLB-1,MLB-6,Aspergillus terreus and non-sporulating dematiaceous form of fungi were prominent in improving plant growth.This has also been confirmed the useful and beneficial impact of indigenous organism.The records made during the study is useful for development of bioinoculants for forest trees,nursery of quality planting material which will also helps in establishment at plantation site.

PGPR调控植物响应逆境胁迫的作用机制

盐碱、干旱等非生物胁迫是限制植物生长和产量的重要环境因子。植物根际促生菌(PGPR)是一类定殖于植物根系的有益微生物,利用其生物学功能制成的生物菌剂具有低成本、高效和环保等优点,不仅可促进植物生长与作物产量,还能提高植物对非生物胁迫的耐受性。本研究对PGPR定义和种类、生物学功能及其在植物响应盐碱、干旱、高低温及重金属等非生物胁迫中的作用加以综述,并对其未来研究方向进行展望,以期为今后PGPR介导植物抗逆性的研究与生物菌剂的开发和应用提供理论支撑。

溶磷菌剂对玉米幼苗生长及根际土壤细菌群落结构和磷素形态的影响

以FD11(普瑞斯特氏菌Priestia sp.)和CH07(阿氏芽孢杆菌Bacillus aryabhattai)两种溶磷菌剂为试验材料,进行菌剂灌根盆栽试验,测定溶磷菌剂施用对玉米生长、根际土壤养分、土壤微生物特性及土壤不同形态磷含量的影响。结果表明,施用溶磷菌剂可改善根际土壤养分特征和微生物学特性,增加根际土壤的活性磷源含量,对玉米幼苗表现出良好的促生作用。与不施菌剂相比,FD11处理玉米幼苗的株高、茎粗、地上部干重分别增加31.88%、36.39%、104.00%;根际土壤碱解氮、有效磷、速效钾分别增加了21.90%、107.67%、5.77%。施用溶磷菌剂的土壤H_(2)O-Pi(Pi为无机磷)、NaHCO_(3)-P和NaOH-P含量增加,但HCl-Pi和Residual-P含量显著降低。施用溶磷菌剂改变了玉米根际土壤细菌的群落结构,在细菌属分类学水平上,不动杆菌属、假单胞菌属、海洋杆菌属、鞘氨醇单胞菌属、节杆菌属等功能细菌的相对丰度显著增加。综合以上分析,施用溶磷菌剂显著提高了土壤速效养分含量,改变了根际土壤细菌的群落结构,增加了活性磷源的含量,从而改善了土壤肥力,促进玉米根系发育和幼苗生长。此项研究可为新型微生物菌肥的研发提供理论依据。

解磷生物肥对设施土壤养分及细菌群落结构的影响

为了揭示解磷生物肥对设施土壤养分及细菌群落结构的影响,将解磷菌P623-9与腐熟鸡粪复配,制成解磷生物肥,盆栽试验以设施土壤作为研究对象,以北方温室广泛栽培的辣椒为试验材料,设置4个处理:CK:空白对照;SY:解磷生物肥3000 kg/hm^(2);Y:腐熟鸡粪3000 kg/hm^(2);S:解磷菌240 L/hm^(2)。采用传统统计学方法对土壤养分含量进行统计分析,结果表明,SY处理的土壤中AP、TN、MBC、MBN及MBP含量均增加,与其他处理相比呈现显著增加差异(P<0.05);采用Illumina Miseq高通量测序分析土壤细菌丰度、群落结构及差异特征,结果显示,门水平中放线菌门(Actinobacteria)、芽单胞菌门(Gemmatimonadetes)、绿弯菌门(Chlo-roflexi)、拟杆菌门(Bacteroidetes)、厚壁菌门(Firmicutes)、酸杆菌门(Acidobacteria)、变形菌门(Proteobacteria)为优势菌门,SY处理的土壤样品中变形菌门、厚壁菌门和绿弯菌门细菌相对丰度较高;属水平中相对丰度较高的依次为芽胞杆菌(Bacillus)、节杆菌(Arthrobacter)、刺单胞菌(Sphingomonas)、链霉菌(Streptomyces)。SY处理的土壤中相对丰度较高为Arthrobacter(3.95%),与对照组相比丰度上升。Beijerinckiaceae与有效磷、全氮、微生物量磷、微生物量氮存在正相关,与总磷存在负相关;Nocardioidaceae与微生物氮存在显著正相关,但与全氮和有效磷的相关性较弱;Microscillaceae与全氮、微生物量碳、微生物量氮、微生物量磷等均存在正相关。由此得出结论,施用解磷生物肥能够显著提高土壤养分含量,增加有益菌群丰度和细菌菌群多样性。本研究揭示了施用解磷生物肥对设施土壤养分及细菌群落多样性的影响,为市场化应用和推广提供参考。

丛枝菌根真菌和解磷细菌双接种对小麦磷肥利用率的影响

试验采用单因素随机区组设计,以接种复合灭活菌剂为对照,分析了2种丛枝菌根真菌(Rhizoph-agus irregularis,RI;Glomus intraradices,GI)和4种解磷细菌(Bacillus amyloliquefaciens,BA;Bacillus megate-rium,BM;Arthrobacter pascens,AP;Bacillus subtilis,BS)双接种对小麦生长和磷肥利用率的影响。结果表明:(1)与对照相比,接菌组小麦的菌根侵染率、产量、速效磷含量均显著提高,而土壤pH值显著下降,小麦产量和速效磷含量在接菌处理下分别提高了7.31%~27.00%和19.03%~60.35%。(2)GI+AP处理的产量最高,添加RI接菌组的速效磷含量、碱性磷酸酶活性均高于添加GI的接菌组,其中以RI+BS处理的最高;RI+BS和RI+BA处理的磷肥吸收利用率最高,分别为30.86%和27.94%。(3)相关性分析结果表明,小麦磷肥吸收利用率与菌根侵染率、籽粒重、籽粒磷含量、速效磷含量、碱性磷酸酶活性呈极显著正相关,与叶片磷含量呈显著正相关,与土壤pH值呈极显著负相关。综上,双接种丛枝菌根真菌和解磷细菌有利于增强土壤碱性磷酸酶活性、增加土壤速效磷含量、降低土壤pH值,从而提高小麦产量和磷素积累量,其中RI+BS处理对小麦磷肥利用率的提高作用最为显著。

解磷细菌解磷机制研究进展及其在水稻上的应用

磷是植物生长不可缺少的元素。土壤中总磷含量丰富,但可被植物直接吸收利用的有效磷含量却很低。传统上主要通过施用磷肥提高缺磷地区的作物产量。然而,施入土壤中的磷不仅易被固定,还会转化成难以被植物直接吸收利用的有机磷,从而降低植物对磷的吸收利用率,造成环境污染。解磷细菌具有将土壤中难溶态磷转化为可被植物直接吸收利用的有效磷的功能,提高植物对磷的吸收利用率。解磷细菌种类繁多,作用机制复杂且影响因素众多。本文综述了解磷细菌解磷机制的研究进展,总结了解磷细菌在水稻生产上的应用情况,以为提高稻田土壤难溶态磷的利用效率提供理论依据。

九种牡丹根际土壤中解有机磷细菌的筛选及解磷能力评价

牡丹作为我国重要的原生植物资源,具有较大的理论研究和开发应用价值。探索资源高效、环境友好的施肥管理方式更有利于促进牡丹产业的绿色可持续发展。本研究以9种牡丹的根际土壤为材料,利用平板稀释法对根际土壤中具有解有机磷能力的细菌进行分离筛选,并采用16S rRNA基因测序技术鉴定菌株种类,结合溶磷圈法和钼锑抗比色法评价菌株的解磷能力。结果表明:从9种牡丹的根际土壤中筛选出14株解有机磷细菌,包括假单胞菌属3株,节杆菌属3株,贪铜菌属3株,芽孢杆菌属2株,红球菌属1株,链霉菌属1株,固氮菌属1株。不同解有机磷菌株的溶磷指数在1.5—2.9,溶磷效率为54.6%—194.6%,对应培养液中的速效磷含量在0.060—5.853 mg∕L,对植酸钙的活化率为30.48%—91.22%,其中,从杨山牡丹根际土壤中分离的菌株PO15(隶属于芽孢杆菌属)的溶磷指数、溶磷效率和速效磷含量均最高,其降解有机磷的能力最强。该研究对牡丹高效解磷菌株的筛选及专用微生物菌肥的研发具有重要的参考价值,也为实现牡丹产业绿色发展提供了新的思路和理论支撑。

解磷细菌活化水稻土中低品位磷矿粉的效果与机制

【目的】低品位磷矿粉中磷的生物利用具有重要意义。探讨解磷细菌活化低品位磷矿粉的效果与机制,为提高磷矿粉在红壤性水稻土上的施肥效果提供依据。【方法】将在湖南省采集的红壤性水稻土中添加不同粒径(0.18、0.10和0.05 mm)的磷矿粉,设置接种乙酸钙不动杆菌(Acinetobacter calcoaceticus,P1)、皮特不动杆菌(Acinetobacter pittii,P2),以及不接种解磷细菌(P0)3种处理。将培养瓶在25℃黑暗培养箱中培养60 d,期间动态监测不同形态磷、pH,第60天测定有机酸、酸性和碱性磷酸酶活性(ACP、ALP)、碱性磷酸酶基因(phoD),研究解磷细菌对不同粒径磷矿粉的活化效果及机制。【结果】两株解磷细菌均能够活化难溶性磷,活化效果差异不显著。整个培养期间,3个粒径的磷矿粉接种解磷细菌后有效磷平均含量为13.4—14.7 mg·kg^(-1),高于不接种(P0)处理,提高31.1%—53.1%。粒径0.05 mm磷矿粉接种P1和P2解磷菌后有效磷平均含量增幅最大,为53.1%、47.5%(P<0.05);树脂磷(Resin-Pi)和碳酸氢钠提取无机磷(NaHCO3-Pi)的平均含量分别为13.9—16.6和14.9—16.5 mg·kg^(-1),均高于P0处理,分别提高36.4%—78.5%和13.7%—25.0%。粒径0.18 mm磷矿粉接种P1和P2解磷菌后Resin-Pi平均含量增幅最明显,为78.5%、49.5%(P<0.05);与P0相比,接种解磷细菌后粒径0.18 mm磷矿粉处理的活性磷增幅最明显,为28.4%—46.7%,稳定性磷降低2.1%—8.0%。与P0相比,接种解磷细菌土壤pH降低0.18—0.35个单位(P<0.05);乙酸、丙酸含量提高5.2%—13.7%和45.9%—127.5%(P<0.05)。P1处理碱性磷酸酶含量、phoD丰度分别增加6.5%—13.4%和24.0%—98.6%(P<0.05),P2处理酸性磷酸酶活性增加12.8%—17.2%(P<0.05),表明P1主要分泌碱性磷酸酶,P2主要分泌酸性磷酸酶。相关性分析结果表明,两株解磷细菌主要通过分泌乙酸、丙酸溶解难溶性的浓盐酸提取有机磷(Conc.HCl-Po)、浓盐酸提取无机磷(Conc.HCl-Pi)和氢氧化钠提取无机磷(NaOH-Pi),分泌酸性磷酸酶与碱性磷酸酶溶解难溶性有机磷(Conc.HCl-Po),向活性较高的Resin-Pi和碳酸氢钠提取无机磷(NaHCO_(3)-Pi)转化,促进磷库的周转。结构方程模型表明,添加细小粒径的磷矿粉与接种解磷细菌均可直接提高土壤有效磷含量,但接种解磷细菌对有效磷的影响更大。【结论】接种解磷菌能促进磷矿粉中难溶性磷的活化,粒径0.05 mm磷矿粉接种解磷菌后土壤有效磷增幅最大,但粒径0.18 mm磷矿粉处理的活性磷占比增幅最大,活化效果最好。解磷细菌乙酸钙不动杆菌和皮特不动杆菌主要通过分泌乙酸、丙酸等有机酸及磷酸酶,活化难溶性磷,增加活性磷占比,提高磷矿粉在红壤性水稻土中的施用效果。