Isolation Of Plant Growth-promoting Bacteria Research Articles

Soil and root microbiome analysis and isolation of plant growth-promoting bacteria from hybrid buffaloberry (Shepherdia utahensis 'Torrey') across three locations.

The effects of climate change are becoming increasingly hazardous for our ecosystem. Climate resilient landscaping, which promotes the use of native plants, has the potential to simultaneously decrease the rate of climate change, enhance climate resilience, and combat biodiversity losses. Native plants and their associated microbiome form a holo-organism; interaction between plants and microbes is responsible for plants' growth and proper functioning. In this study, we were interested in exploring the soil and root microbiome composition associated with Shepherdia utahensis, a drought hardy plant proposed for low water use landscaping, which is the hybrid between two native hardy shrubs of Utah, S. rotudifolia and S. argentea. The bulk soil, rhizosphere, root, and nodule samples of the hybrid Shepherdia plants were collected from three locations in Utah: the Logan Campus, the Greenville farm, and the Kaysville farm. The microbial diversity analysis was conducted, and plant growth-promoting bacteria were isolated and characterized from the rhizosphere. The results suggest no difference in alpha diversity between the locations; however, the beta diversity analysis suggests the bacterial community composition of bulk soil and nodule samples are different between the locations. The taxonomic classification suggests Proteobacteria and Actinobacteriota are the dominant species in bulk soil and rhizosphere, and Actinobacteriota is solely found in root and nodule samples. However, the composition of the bacterial community was different among the locations. There was a great diversity in the genus composition in bulk soil and rhizosphere samples among the locations; however, Frankia was the dominant genus in root and nodule samples. Fifty-nine different bacteria were isolated from the rhizosphere and tested for seven plant growth-promoting (PGP) traits, such as the ability to fix nitrogen, phosphates solubilization, protease activity, siderophore, Indole Acetic Acid (IAA) and catalase production, and ability to use ACC as nitrogen source. All the isolates produced some amount of IAA. Thirty-one showed at least four PGP traits and belonged to Stenotrophomonas, Chryseobacterium, Massilia, Variovorax, and Pseudomonas. We shortlisted 10 isolates that showed all seven PGP traits and will be tested for plant growth promotion.

Isolation and Identification of Growth-Promoting Bacteria from Plants Growing Under Abiotic Stresses.

Identification and isolation of plant growth-promoting bacteria (PGPB) are critical steps toward understanding the role of these bacteria in stress tolerance in plants. This procedure also provides essential knowledge about the microbes needed to formulate effective biofertilizers. This chapter describes culture-dependent and culture-independent strategies to identify and isolate PGPB. The culture-dependent strategy commonly involves growing PGPB on general and selective media. However, the culture-independent strategy involves next-generation sequencing technologies. A combination of both strategies would identify the structure of the bacterial communities and isolate bacteria from their environments. Therefore, this chapter describes a comprehensive strategy where the methods are sequentially applied to identify and isolate epiphytic and endophytic PGPB from a particular environmental sample. However, a single procedure can also be employed to identify and isolate a specific type of PGPB.

Plant-growth-promoting bacteria from rhizosphere of Chilean common bean ecotype (Phaseolus vulgaris L.) supporting seed germination and growth against salinity stress.

Salinity abiotic stress is increasing day by day due to continuous global warming and climate change. This is also becoming one of the major causes behind the reduction in crop production. Plant-bacteria interaction plays an essential role in improving crop yield without using any chemical fertilizers. The present study aims to characterize the interaction between plant-growth-promoting bacteria (PGPB) and their role in mitigating salinity stress for local variety crops. Therefore, in this work, two PGPB, namely, Bacillus proteolyticus Cyn1 and Bacillus safensis Cyn2, were isolated from rhizospheric soil of the Chilean common bean ecotype "Sapito" (Phaseolus vulgaris L.), and their PGPB traits were analyzed. Cyn1 can produce NH3 and HCN and also secrete siderophores, whereas Cyn2 produced NH3 and siderophores but responded negatively to HCN production. Both the isolated bacteria have shown a positive result for ACC deaminase production, phosphate solubilization, and catalase enzyme secretion. Under all three tested abiotic stresses, i.e., temperature, water, and salinity, both the bacteria and their consortium have demonstrated positive responses. Cyn1 under temperature stress and water stress can produce a biofilm network to combat the stress. While under salinity stress, both the PGPB isolates indicated the production of stress components and cytoplasmic inclusion bodies. Based on the response, among all other abiotic stresses, salinity stress was chosen for further plant-bacteria interaction study and growth. Visible root colonization of the bacteria has been observed in comparison to the control. The germination index was 100% for all experimental setups of seed bacterization, both under control conditions and salinity stress. Both bacteria responded with good PGP traits that helped in the growth of healthy plants after the bacterial treatment in final pot experiments. Additionally, the consortium and the plants treated with Cyn1 have demonstrated high production of photosynthetic pigments in both experimental setups. Both B. proteolyticus Cyn1 and B. safensis Cyn2 have shown promising PGP characters and efficient response against toxicity related to salinity. Hence, both of these bacteria and consortium can be used for improved agricultural production of Chilean native common beans in the near future.

Effect of Plant Growth Promoting Bacteria on Growth and Nutrient Content of Rice

Aims: The application of a huge number of chemical fertilizers for crop production alters the sustainability of the environment and creates pollution. This problem can be minimized by the application of Plant Growth Promoting Bacteria (PGPB). Plant Growth Promoting Bacteria (PGPB) are beneficial bacteria that promote plant growth and development through a variety of mechanisms. Therefore, a pot experiment was conducted at the department of Soil Science, BSMRAU to investigate the effect of different PGPB isolates on growth, nutrient content, and uptake by rice.
 Materials and Methods: The experiment was carried out following a completely randomized design (CRD) with four replicates. Twenty bacterial isolates were used as treatments with a control treatment. Thirty-five days old seedlings of rice were inoculated with different bacterial isolates for thirty minutes and planted in a plastic pot. Broth culture was applied at one-month intervals and crops were harvested 65 days after planting.
 Results: Experimental results disclose that application of PGPB isolates resulted in a significant increase in plant height, SPAD value, root length, root volume, straw fresh weight, straw dry weight, root fresh weight, root dry weight, nutrient content and uptake by the rice plant compare to control. The highest values of most of the parameters were recorded from the plant inoculated with the isolate BU Ls 28.
 Conclusion: The present study suggests that the use of PGPB isolate BU Ls 28 might be used as a suitable inoculant for rice production due to the ability of this isolate to promote plant growth.

Halotolerant Plant Growth-Promoting Bacteria Colonization of Agronomic Crops Under Saline Stress

The ability of a plant growth-promoting bacteria (PGPB) strain to colonize the roots and tissues of inoculated plants is important for their successful use in agricultural practices. The purpose of this study was to determine how effective 15 indigenous halotolerant PGPB were at colonizing three different agronomic crops via seed inoculation. Using standard Hoagland’s media and Hoagland’s media amended with 100 mM NaCl, we tested 15 gfp-tagged halotolerant bacterial isolates for their ability to colonize rice, maize, and soybean seedlings. The quantitative dilution plating method and fluorescent microscopy were used to determine the colonization degree of gfp-tagged halotolerant PGPB isolates in the rhizoplane zone and in the inner tissue of the seedlings at 21 days after germination. All halotolerant PGPB isolates colonized the rhizoplane zone of all seedlings. In both standard and 100 mM NaCl amended Hoagland’s media, isolates E194-3, D183-4, and E101-1 showed the highest colonization in rice, maize, and soybean seedlings, respectively. The ability of halotolerant PGPB isolates to colonize agronomic crops was found to vary depending on bacterial isolates, plant species, plant tissues, and NaCl concentration.
 Keywords: inoculation, colonization, halotolerant, endophyte, rhizoplane

Effect of Nitrogen-fixing Bacteria on Germination, Seedling Vigour and Growth of Two Rice (Oryza sativa L.) Cultivars

To evaluate the effect of isolated nitrogen fixing plant growth-promoting bacteria (PGPB) on seed germination and growth promotion of rice cultivars (cv. BPT 5204 and Improved Samba Mahsuri). Eight promising N-fixing PGPB along with two standard cultures (viz. B. japonicum and G. diazotrophicus) were inoculated as seed treatment to rice genotypes and the effect on seed germination, seed vigour index and plant growth promotion of rice cultivars was assessed under in vitro (agar method) and in vivo (pot experiment) net house conditions. PGPBs (viz., Paenibacillus sonchi IIRRBNF1, Paenibacillus sp. IIRRNF2, Ochrobactrum sp. IIRRNF3, Burkholderia cepacia IIRRNF4, Burkholderia sp. IIRRNF5, Stenotrophomonas sp. IIRRNF6, Rhizobium sp. IIRRNF7 and Xanthomonas sacchari IIRRNF8) were enhanced seed germination, seed vigour index, seedling growth and dry matter accumulation (root and shoot dry matter) of rice cultivars under in vitro as well as in vivo conditions. Among all PGPB, Paenibacillus sonchi IIRRBNF1 exhibited the highest ability to stimulate plant growth promotion under both the conditions. The eight PGPB isolates exhibited positive influence on seed germination indices as well as growth promotion traits of rice cultivars at seedling stage and can be further evaluated at different growth stages under pot and field experiment.

Isolation and Characterization of Beneficial Bacteria from Food Process Wastes.

Significant quantities of food waste are accumulated globally on an annual basis, with approximately one-third of the food produced (equivalent to 1.3 billion tons of food) being wasted each year. A potential food waste recycling application is its utilization as a soil conditioner or fertilizer, whereby it increases the soil organic content and microbial biomass. This study evaluated the effectiveness of food waste as a microbial resource by analyzing the microbial community composition and isolating plant growth-promoting bacteria (PGPB) in food waste obtained from various sources. High-throughput sequencing identified 393 bacterial operational taxonomic units in the food process waste (FPW) samples. Moreover, the results showed that Firmicutes was abundant in the waste samples, followed by Bacteroidetes and Proteobacteria. A total of 92 bacteria were isolated from FPW. Moreover, the cultivable strains isolated from FPW belonged to the genus Bacillus, followed by Streptomyces and Proteus. Six isolated bacteria exhibited beneficial traits, including indole acetic acid production, antifungal resistance and extracellular lysis. FPW is a valuable microbial resource for isolation of PGPB, and its use as a fertilizer may enable a reduction in chemical fertilizer usage, thereby mitigating the corresponding adverse environmental impacts on sustainable crop development.

Mining the Microbiome of Key Species from African Savanna Woodlands: Potential for Soil Health Improvement and Plant Growth Promotion.

(1) Aims: Assessing bacterial diversity and plant-growth-promoting functions in the rhizosphere of the native African trees Colophospermum mopane and Combretum apiculatum in three landscapes of the Limpopo National Park (Mozambique), subjected to two fire regimes. (2) Methods: Bacterial communities were identified through Illumina Miseq sequencing of the 16S rRNA gene amplicons, followed by culture dependent methods to isolate plant growth-promoting bacteria (PGPB). Plant growth-promoting traits of the cultivable bacterial fraction were further analyzed. To screen for the presence of nitrogen-fixing bacteria, the promiscuous tropical legume Vigna unguiculata was used as a trap host. The taxonomy of all purified isolates was genetically verified by 16S rRNA gene Sanger sequencing. (3) Results: Bacterial community results indicated that fire did not drive major changes in bacterial abundance. However, culture-dependent methods allowed the differentiation of bacterial communities between the sampled sites, which were particularly enriched in Proteobacteria with a wide range of plant-beneficial traits, such as plant protection, plant nutrition, and plant growth. Bradyrhizobium was the most frequent symbiotic bacteria trapped in cowpea nodules coexisting with other endophytic bacteria. (4) Conclusion: Although the global analysis did not show significant differences between landscapes or sites with different fire regimes, probably due to the fast recovery of bacterial communities, the isolation of PGPB suggests that the rhizosphere bacteria are driven by the plant species, soil type, and fire regime, and are potentially associated with a wide range of agricultural, environmental, and industrial applications. Thus, the rhizosphere of African savannah ecosystems seems to be an untapped source of bacterial species and strains that should be further exploited for bio-based solutions.

Enhancing Application Efficiency of Pseudomonas SPP. and Serratia marcescens Isolates against Meloidogyne incognita in Tomato Plants.

To preserve environmental resources and ensure their sustainability, the search for natural and safe alternatives for controlling pests that attack crops is an urgent necessity. So, the feasibility evaluation of applying plant growth-promoting bacteria (PGPB) isolates as self-reproducing bioagent in controlling root-knot nematodes, Meloidogyne incognita is needed, and compare their effect with traditional control methods in the laboratory and greenhouse. Obtained data revealed that egg masses hatching was inhibited by 64.51% when treated with Pseudomonas putida/fluorescens isolates, while, decreased to 39.34%with Serratia marcescens isolates treatment. While the larvicidal effect of Pseudomonas isolates was 99.34% and 88.36 in S. marcescens isolates treatments. The tested PGPB showed mediated ovicidal and larvicide lower than oxamyl and higher than composted cattle manure extract (CCME) with surpassing the larvicidal effect. In the greenhouse experiment, all tomato growth parameters measurement data increased especially in treatments: the combination of PGPB isolates + CCM followed by P. putida/fluorescens + S. marcescens isolates then oxamyl treatment and the lowest increases were the CCM treatment. The inoculation of the tested PGPB isolates + CCM and oxamyl application reduced highly galling reduction percentage and reproduction (IJs/100 g soil) of M. incognita as compared withCCM with a percent reduction of 50.52% (86.07), 58.71% (77.78), and 24.99% (46.26), respectively. Therefore, the results confirm the feasibility and effectiveness of mixing PGPB isolates with manure or its derivatives, better than the individual application of PGPB or manure. The inoculation of the tested PGPB isolates + CCM and oxamyl application reduced highly galling reduction percentage and reproduction (IJs/100 g soil) of M. incognita as compared withCCM with a percent reduction of 50.52% (86.07), 58.71% (77.78), and 24.99% (46.26), respectively. Therefore, the results confirm the feasibility and effectiveness of mixing PGPB isolates with manure or its derivatives, better than the individual application of PGPB or animal manure.

Agricultural Utilization of Unused Resources: Liquid Food Waste Material as a New Source of Plant Growth-Promoting Microbes

Organic amendment is important for promoting soil quality through increasing soil fertility and soil microbes. This study evaluated the effectiveness of using liquid food waste material (LFM) as a microbial resource, by analyzing the microbial community composition in LFM, and by isolating plant growth-promoting bacteria (PGPB) from the material. High-throughput sequencing of LFM, collected every month from May to September 2018, resulted in the detection of >1000 bacterial operational taxonomic units (OTUs) in the LFM. The results showed that Firmicutes was abundant and most frequently detected, followed by Proteobacteria and Actinobacteria. Of the culturable strains isolated from LFM, almost all belonged to the genus Bacillus. Four strains of PGPB were selected from the isolated strains, with traits such as indole acetic acid production and 1-aminocyclopropane-1-carboxylic acid deaminase activity. Lettuce growth was improved via LFM amendment with PGPB, and Brassica rapa showed significant differences in root biomass when LFM amendment was compared with the use chemical fertilizer. Field experiments using LFM showed slight differences in growth for Brassica rapa, lettuce and eggplant, when compared with the use of chemical fertilizer. LFM is a useful microbial resource for the isolation of PGPB, and its use as fertilizer could result in reduced chemical fertilizer usage in sustainable agriculture.

Bacterial Consortium for Improved Maize (Zea mays L.) Production.

The ever-increasing human population is a major concern for food security. Maize is the third largest most important food crop. The major problems of cultivation arise from urbanization and land pollution. This reduces the amount of land available for agriculture. The use of chemicals in agriculture is not environmentally friendly. Thus, plant growth-promoting bacteria (PGPB) have been proposed as alternatives. This study aims to test the growth-promoting effect of maize inoculated with six indigenous PGPB isolates. These isolates were assayed for various biochemical and plant growth-promoting activities. They were also assayed for biocontrol activities. Based on the results, six isolates viz A1, A18, A29, NWU4, NWU14, and NWU198 were used to inoculate maize seeds. The inoculated seeds were tried out on the field. A randomized block design was used. PGPB used were in single, consortia of two, and three organisms. The length of the leaves, roots, and stem, plant height, numbers of leaves, and weight of 100 seeds were taken at the fourth and eighth weeks after planting. Microbial consortia increased growth parameters compared to single inoculant treatments. Thus, they can be of advantage in the eradication of low yield. They can also serve as reliable alternatives to chemical fertilizers.

Nutrient enhancement of chickpea grown with plant growth promoting bacteria in local soil of Bathinda, Northwestern India.

Plant growth promoting bacteria (PGPB) enhance crop productivity as part of green technology to reduce the use of chemical fertilizers. They also have the capability to enhance macro- and micronutrient content of plants. In the present study, PGPB isolates belonging to Pseudomonas citronellis (PC), Pseudomonas sp. RA6, Serratia sp. S2, Serratia marcescens CDP13, and Frateuria aurantia (Symbion-K) were tested on two chickpea varieties, PBG1 and PBG5 grown for 30days in local soil from Bathinda region in Northwestern India. PC and CDP13 were found to be better chickpea growth stimulators compared to the commercial Symbion-K based on shoot length and biomass. Most PGPB enhanced macro- and micronutrients in shoots to varying degrees compared to the control. PBG5 gave better response compared to PBG1 with reference to plant growth attributes and enhancement of the macronutrients, calcium, nitrogen and phosphorus and micronutrients, boron, copper, iron, and zinc. PBG5 is a high yielding variety with better resistance compared to PBG1. Overall, PGPB isolated from the local soil and PGPB from other parts of India were shown to be useful for enhancement of nutrient content and plant growth.

Plant growth-promoting endophytic bacteria on maize and sorghum1

ABSTRACT Plant growth-promoting bacteria (PGPB) are found in plant tissues and promote plant growth by secretion of hormones and enzymes, or by facilitating the nutrient uptake. This study assessed forty PGPB isolates to determine their effects on maize and sorghum growth. These isolates were also compared with uninoculated plants, as negative (-N; without N fertilization) and positive (+N; with N fertilization) controls. Plant height, stem diameter, shoot and root dry mass, leaf N accumulation and chlorophyll content were evaluated. For both the maize and sorghum, the height, stem diameter and shoot dry mass in plants inoculated with PGPB were similar to those of uninoculated plants supplied with N, and the responses for root mass were higher than in plants supplied with N. However, the PGPB isolates did not promote N accumulation and chlorophyll content similar to those of uninoculated plants supplied with N. The IPACC26 and IPACC30 isolates, both identified as Bacillus subtilis, resulted in better responses for plant growth and N accumulation than the other isolates.

Plant growth promoting bacteria increases biomass, effective constituent, and modifies rhizosphere bacterial communities of Panax ginseng

ABSTRACTPurpose: The main aim of this study was to introduce and explore plant growth-promoting bacteria (PGPB) indigenous to ginseng, and to evaluate their ability to improve production and quality, and effect on rhizosphere niche in ginseng.Materials and methods: Endophytic bacteria were isolated from root, stem, and leaf of ginseng from different sites and genotype in China and Korea, screened based on their beneficial properties as PGPB. Nine bacterial isolates were selected according to their plant growth properties including soluble phosphate and potassium, ammonia, auxin and siderophore producing, ACC deaminase, and antagonistic pathogen as well. Changes in ginseng after PGPB inoculation were evaluated with respect to the non-inoculated control.Results and Conclusions: The PGPB isolates were identified as genera Bacillus, Lysinibacillus, Rhizobium, Stenotrophomonas, Erwinia, Ochrobactrum, Enterobacter and Pantoea based on 16S rRNA sequences. Inoculation of G209 and G119 increased not only plant height, root length, fresh weight, and dry weight, but also root activity and the amount of ginsenosides significantly. In particular, using the Illumina Miseq platform, the native bacterial community of rhizospheric soil maintained high community diversity and increased abundance of specific bacteria. Therefore, they may be play a crucial role in sustainable ginseng cultivating in farmland.

Isolation and characterization of plant growth promoting bacteria (PGPB) from anaerobic digestate and their effect on common wheat (Triticum aestivum) seedling growth

The use of anaerobic digestate as fertilizer is considered beneficial since it provides plant nutrients and organic matter to soils. However, there is limited information about plant growth promoting bacteria (PGPB) in digestate. In this study, we isolated Bacillus and Pseudomonas from two types of anaerobic digestates, and selected three different plant growth promoting traits and antifungal activity to screen 200 bacteria isolated from each digestate. Then 6 isolates based on plant growth promoting traits were selected and inoculated with common wheat seeds to evaluate their plant growth promoting activity. Cultivable population of Bacillus and Pseudomonas were 2.20 × 106 and 6.98 × 104 CFU g-1 dry matter in mesophilic digestate, while were 6.86 × 105 and 5.65 × 104 CFU g-1 dry matter in thermophilic digestate. Twenty-five bacterial isolates from mesophilic digestate and 12 bacterial isolates from thermophilic digestate showed positive plant growth promoting traits or antifungal activity. In plant growth promoting assay, all isolates significantly promoted growth of wheat seedlings (p less than 0.05). Seedlings stem length was increased from 28.5% to 38.6% by bacteria inoculation. In addition, bacteria inoculation increased seedlings stem weight from 113.3% to 214.2% and root weight from 108.6% to 207.2% as compared to un-inoculated control. The results showed that anaerobic digestate was a potential source for isolation of PGPB, and PGPB in digestate would be beneficial for plant growth with fertilizer application.

Plant Growth-Promoting Bacteria for Phytostabilization of Mine Tailings

Eolian dispersion of mine tailings in arid and semiarid environments is an emerging global issue for which economical remediation alternatives are needed. Phytostabilization, the revegetation of these sites with native plants, is one such alternative. Revegetation often requires the addition of bulky amendments such as compost which greatly increases cost. We report the use of plant growth-promoting bacteria (PGPB) to enhance the revegetation of mine tailings and minimize the need for compost amendment. Twenty promising PGPB isolates were used as seed inoculants in a series of greenhouse studies to examine revegetation of an extremely acidic, high metal contenttailings sample previously shown to require 15% compost amendment for normal plant growth. Several isolates significantly enhanced growth of two native species, quailbush and buffalo grass, in tailings. In this study, PGPB/compost outcomes were plant specific; for quailbush, PGPB were most effective in combination with 10% compost addition while for buffalo grass, PGPB enhanced growth in the complete absence of compost. Results indicate that selected PGPB can improve plant establishment and reduce the need for compost amendment. Further, PGPB activities necessary for aiding plant growth in mine tailings likely include tolerance to acidic pH and metals.