Plant Growth-promoting Properties Research Articles

Insight into the genome of an arsenic loving and plant growth-promoting strain of Micrococcus luteus isolated from arsenic contaminated groundwater.

Contamination of arsenic in drinking water and foods is a threat for human beings. To achieve the goal for the reduction of arsenic availability, besides conventional technologies, arsenic bioremediation by using some potent bacteria is one of the hot topics for researchers. In this context, bacterium, AKS4c was isolated from arsenic contaminated water of Purbasthali, West Bengal, India, and through draft genome sequence; it was identified as a strain of Micrococcus luteus thatcomprised of 2.4Mb genome with 73.1% GC content and 2256 protein coding genes. As the accessory genome, about 22 genomic islands (GIs) associated with many metal-resistant genes were identified. This strain was capable to tolerate more than 46,800mg/L arsenate and 390mg/L arsenite salts as well as found to be tolerable to multi-metals such as Fe, Pb, Mo, Mn, and Zn up to a certain limit of concentrations. StrainAKS4c was able to oxidize arsenite to less toxic arsenate, and its arsenic adsorption property was qualitatively confirmed through X-ray fluorescence (XRF) and Fourier transform infrared spectroscopy (FTIR) analysis. Quantitative estimation of plant growth-promoting attributes like Indole acetic acid (IAA), Gibberellic acid (GA), and proline production and enhancement of rice seedling growth in laboratory condition leads to its future applicability in arsenic bioremediation as a plant growth-promoting rhizobacteria (PGPR).

Multifarious Plant Growth-Promoting Rhizobacterium Enterobacter sp. CM94-Mediated Systemic Tolerance and Growth Promotion of Chickpea (Cicer arietinum L.) under Salinity Stress.

Chickpea is one of the most important leguminous crops and its productivity is significantly affected by salinity stress. The use of ecofriendly, salt-tolerant, plant growth-promoting rhizobacteria (PGPR) as a bioinoculant can be very effective in mitigating salinity stress in crop plants. In the present study, we explored, characterized, and evaluated a potential PGPR isolate for improving chickpea growth under salt stress. A potential PGPR was isolated from rhizospheric soils of chickpea plants grown in the salt-affected area of eastern Uttar Pradesh, India. The isolate was screened for salt tolerance and characterized for its metabolic potential and different plant growth-promoting attributes. Further, the potential of the isolate to promote chickpea growth under different salt concentrations was determined by a greenhouse experiment. A rhizobacteria isolate, CM94, which could tolerate a NaCl concentration of up to 8% was selected for this study. Based on the BIOLOG carbon source utilization, isolate CM94 was metabolically versatile and able to produce multiple plant growth-promoting attributes, such as indole acetic acid, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, siderophore, hydrogen cyanide (HCN), and ammonia as well as solubilized phosphate. A polyphasic approach involving the analysis of fatty acid methyl ester (FAME) and 16S rRNA gene sequencing confirmed the identity of the isolate as Enterobacter sp. The results of greenhouse experiments revealed that isolate CM94 inoculation significantly enhanced the shoot length, root length, and fresh and dry weight of chickpea plants, under variable salinity stress. In addition, inoculation improved the chlorophyll, proline, sugar, and protein content in the tissues of the plant, while lowering lipid peroxidation. Furthermore, isolate CM94 reduced oxidative stress by enhancing the enzymatic activities of superoxide dismutase, catalase, and peroxidase compared to in the respective uninoculated plants. Overall, the results suggested that using Enterobacter sp. CM94 could significantly mitigate salinity stress and enhance chickpea growth under saline conditions. Such studies will be helpful in identifying efficient microorganisms to alleviate salinity stress, which in turn will help, to devise ecofriendly microbial technologies.

Methylobacterium spp. mitigation of UV stress in mung bean (Vigna radiata L.).

Methylotrophs are a diverse group of bacteria that abundantly colonize the phyllosphere and have great potential to withstand UV irradiation because of their pigmented nature and ability to promote plant growth through various mechanisms. The present study investigated the effects of UVB radiation on plant growth-promoting (PGP) properties of methylotrophic bacteria and the growth of Vigna radiata L. A total of 55 methylotrophic bacteria were isolated from desert plants, and 15 methylotrophs were resistant to UVB radiation for 4h. All UVB-resistant methylotrophs possess a methyldehydrogenase gene. Identification based on 16S rRNA gene sequencing revealed that all 15 UVB-resistant methylotrophs belonged to the genera Methylorubrum (07), Methylobacterium (07), and Rhodococcus (01). Screening of methylotrophs for PGP activity in the presence and absence of UVB radiation revealed that all isolates showed ACC deaminase activity and growth on a nitrogen-free medium. Furthermore, the production of IAA-like substances ranged from 8.62 to 85.76µg/mL, siderophore production increased from 3.47 to 65.75% compared to the control. Seed germination assay with V. radiata L. (mung bean) exposed to UVB radiation revealed that methylotrophs improved seed germination, root length, and shoot length compared to the control. The present findings revealed that the isolates SD3, SD2, KD1, KD5, UK1, and UK3 reduced the deleterious effects of UVB radiation on mung bean plants and can be used to protect seedlings from UVB radiation for sustainable agriculture.

Proteobacterial dominance in endophytic bacterial diversity in switchgrass growing under nitrogen range and effect on plant growth

Switchgrass (Panicum virgatum L.) is native to North America and cultivated as a forage and bioenergy crop. Inorganic fertilizers enhance biomass production, increase production costs, and pollute the environment. Switchgrass cultivation using an eco-friendly approach might be achieved by inoculation with beneficial microbes. Therefore, the diversity of cultivable endophytic bacteria from roots and shoots of switchgrass growing under a nitrogen regime was studied. The potential of bacteria for plant growth promotion (PGP) was tested under in vitro conditions. A total of 216 bacterial isolates obtained belonged to four phyla and 33 genera, and most isolates were obtained from plants growing under no (0 kg/ha) or low nitrogen (90 kg/ha) input, rather than higher N (180 kg/ha). Higher numbers of isolates belonged to the phylum Proteobacteria, and genus-wise representation showed the dominance of Pseudomonas, Enterobacter, and rhizobia. Bacterial isolates were tested for PGP properties, e.g. phosphate solubilization, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, Indole Acetic Acid (IAA) production, and nitrogen fixation. Many isolates were positive for one or more PGP properties. In in vitro analysis, selected bacterial isolates were inoculated in two commercial switchgrass cultivars and a showed cultivar-specific response. PGP isolates can be used for pot or field trials and eventually for the sustainable cultivation of switchgrass.

Insights into the plant growth promotion properties of bacterial endophytes isolated from Alternanthera philoxeroides and Eichhornia crassipes from Bellandur lake, India

The presence of macrophytes such as Alternanthera philoxeroides and Eichhornia crassipes in Bellandur Lake, India, has been observed despite the high pollution levels. Our research aims to explore the potential role of endophytes in promoting the growth of these macrophytes in such heavily contaminated environments. In current study, we isolated 20 endophytic bacteria from various parts of A. philoxeroides (12) and E. crassipes (8) plants, including shoots, roots, leaves, and flowers. We found that a significant proportion of endophytes from A. philoxeroides (42 %) and E. crassipes (25 %) produced more than 100 µg/mL of indole acetic acid (IAA). Similarly, the majority of the isolates possessed other plant growth promoting traits like ammonia production, nitrogen fixation, phosphate and potassium solubilization, siderophore production, and ACC deaminase production. Many of these isolates demonstrated extracellular enzyme production and halotolerance properties. We identified Acinetobacter soli ON529869 and Bacillus licheniformis ON506048 as the most effective plant growth promoters among the isolates, which also displayed antifungal properties against Fusarium solani and Cladosporium tenuissimum in vitro. Furthermore, greenhouse trials using these two endophytes revealed their significant plant growth promotion abilities in Amaranthus viridis. The pigment indices were evaluated using CI-710 Leaf Spectrometer. In conclusion, our findings provide compelling evidence for exploring the endophytic microbiomes of macrophytes in polluted areas for sustainable agriculture and bioprospecting of unique traits. This research could lead to the discovery of new and valuable resources for agricultural practices and other applications.

Isolation and Characterisation of Culturable Thermophilic Cyanobacteria from Perak Hot Springs and their Plant Growth Promoting Properties Effects on Rice Seedlings (Oryza sativa L.).

Malaysia is home to a number of hot springs that are rich in microbial diversity including the photosynthetic cyanobacteria. Although this microbial community has been characterised based on metagenomics approach, the culturable thermophilic isolates have not been isolated and characterised extensively. Compared to the mesophiles, information on plant growth promoting (PGP) properties of these thermophiles remain largely untapped. As the amount of arable land for microbial bioprospecting is decreasing due to extensive human activities, the search for alternative source for microbial strains with PGP properties is important for the development of potential biofertilisers. This study sought to isolate and characterise culturable cyanobacteria strains from two local hot springs - Sungai Klah (SK) and Lubuk Timah (LT) located in Perak using morphological and molecular methods. The IAA production from the axenic cultures were measured. The PGP properties were also measured by priming the rice seeds with cyanobacterial water extracts. A total of six strains were isolated from both hot springs. Strains LTM and LTW from LT were identified as Leptolyngbya sp. whereas strains SEM, SEH, STH and STM were identified as Thermosynechococcus elongatus. All six strains produced IAA ranged from 670.10 pg/μL to 2010 pg/μL. The water extracts were found to increase the seed amylase activity of the rice seeds from 5th day of germination (DAG) to 10th DAG. In general, the IAA production and increased seed amylase activity might have contributed in enhancing the longest root length, shoot length and root-to-shoot (RS) ratio. To conclude, the thermophilic cyanobacteria from hot springs can be further exploited as a novel source of PGP microbes for the development of biofertilsers.

Genomic insights into Bacillus subtilis MBB3B9 mediated aluminium stress mitigation for enhanced rice growth

Aluminium (Al) toxicity in acid soil ecosystems is a major impediment to crop production as it drastically affects plant root growth, thereby acquisition of nutrients from the soil. Plant growth-promoting bacteria offers an interesting avenue for promoting plant growth under an Al-phytotoxic environment. Here, we report the plant growth-promoting activities of an acid-tolerant isolate of Bacillus subtilis that could ameliorate acid-induced Al-stress in rice (Oryza sativa L.). The whole genome sequence data identified the major genes and genetic pathways in B. subtilis MBB3B9, which contribute to the plant growth promotion in acidic pH. Genetic pathways for organic acid production, denitrification, urea metabolism, indole-3-acetic acid (IAA) production, and cytokinin biosynthesis were identified as major genetic machinery for plant growth promotion and mitigation of Al-stress in plants. The in-vitro analyses revealed the production of siderophores and organic acid production as primary mechanisms for mitigation of Al-toxicity. Other plant growth-promoting properties such as phosphate solubilization, zinc solubilization, and IAA production were also detected in significant levels. Pot experiments involving rice under acidic pH and elevated concentrations of aluminium chloride (AlCl3) suggested that soil treatment with bacterial isolate MBB3B9 could enhance plant growth and productivity compared to untreated plants. A significant increase in plant growth and productivity was recorded in terms of plant height, chlorophyll content, tiller number, panicle number, grain yield, root growth, and root biomass production.

Application of endophytic bacterium Bacillus velezensis BTR11 to control bacterial leaf blight disease and promote rice growth

BackgroundBacterial leaf blight (BLB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most destructive pathogens responsible for severe yield losses in rice. Application of bacterial biocontrol agent (BCA) with plant growth promotion (PGP) abilities is a promising method that alternates current conventional practices to manage BLB disease and increase crop yield. Hence, this study aimed to isolate and identify BCA with PGP abilities from internal plant tissues and rhizosphere soil of healthy and Xoo-infected rice and evaluate their antagonistic and PGP properties under greenhouse and field conditions.ResultsA total of 14 bacterial isolates were isolated and presented in vitro antagonistic ability against the Xoo. The rice endophytic bacterium strain Bacillius velezensis (BTR11) had the highest antagonistic activity against the Xoo, produced indole acetic acid (IAA), and mineralized nutrients (K and P). The greenhouse experiment revealed that culture broth of strain BTR11 had a high protective effect (72.1%) against the BLB when applied at the protective-fighting mode, i.e., before and after the Xoo infection. Preliminary results of the field experiment showed that a protective effect against the bacterial blight disease was obtained as high as 75–85%, if the strain was used as an additive to the soil for the seedlings in combination with spraying when the disease began in the field. In addition, using the strain BTR11 also increased the rice yield to about 12% more than the un-treatment control.ConclusionsThe study showed a significant potential for the application of endophytic bacteria in controlling BLB disease, while stimulating plant growth, thus reducing the use of agrochemicals in rice cultivation.

Heavy metal, salinity and azo dye tolerant, Cr (VI) reducing, plant growth-promoting Pseudomonas aeruginosa R32 reverses Cr (VI) biotoxic effects in Vigna mungo

Hexavalent chromium [Cr (VI)], derived from various industries, including fly ash from coal-based Thermal Power Plants, can be a source of toxic pollution of land and water bodies. This study aimed to bioremediation of such pollutant dump sites using bacteria capable of both Cr(VI) reduction and plant growth-enhancing substance production. The bacteria were isolated from the rhizospheric fly ash of a Thermal Power Plant, Kanpur. One of the rhizospheric isolate, Pseudomonas aeruginosa R32 showed high minimum inhibitory concentration (MIC) for Cr(VI) (1250 µg/ml), heavy metal tolerance (ZnCl2, CdCl2, Pb(NO3)2) up to 100 µg/ml, Acid Red 249 (AR) tolerance and halotolerance (6% NaCl). The isolate R32 also produces plant growth-promoting (PGP) hormones in the absence or presence of Cr (VI). R32 could completely reduce Cr(VI) at a tested dose of 100 and 500 μg/ml after 24h and 72h, respectively. However, decolorization of AR was observed after 48 hours at an initial concentration of 100 µg/ml and confirmed by Fourier transform infrared spectroscopy analysis. Vigna mungo seed inoculation with isolate R32 showed increased rootling growth compared to shoot after 7 d treatment with 0, 100, 500, and 1000 μg/ml of Cr(VI) concentrations, respectively. Root length tolerance index in Cr(VI) treated V. mungo seedlings was reduced to 56%, 35%, and 29%, respectively, when treated with 100, 500, and 1000 μg/ml Cr(VI) in comparison to control. Cr(VI) sub-MIC concentrations can affect the plant growth-promoting properties of rhizospheric bacteria. Herein, we report the isolation of rhizospheric bacteria P. aeruginosa R32 showing concurrent PGP substance production and Cr(VI) bioreduction capabilities in the presence of PGP inhibitory Cr(VI) concentrations.

RECOMBINANT PROTEIN APPLICATION INDUCED DEFENSE MECHANISM IN HOST PLANT AGAINST PAPAYA DIEBACK DISEASE

Erwinia mallotivora is a Gram-negative bacterium that causes the papaya dieback disease in Malaysia. Currently, no effective disease control method is documented. In this regard, the adoption of harpin proteins in promoting plant defense mechanisms has been reported to be a promising control method for this disease. This study used, two recombinant harpin proteins, Hrp I and Hrp II, to control the disease in the glasshouse and field conditions. The results of foliar application in the glasshouse showed protective index of 70.8% and 35.7% for Hrp I and Hrp II, respectively. Meanwhile, the field trial for Hrp I showed a promising protection index of 72.3%. Moreover, the plant growth-promoting attributes were also significantly improved in the case of the Hrp I -treated plants. The effectiveness of Hrp I and II as inducers of systemic acquired resistance (SAR) was further validated by profiling defense-related genes using RT-qPCR analysis. The results showed that the treated papaya plants with Hrp I possess the highest expression of defense genes such as peroxidase, osmotin, and PRID in the glasshouse and field samples. In conclusion, the application of Hrp I is a promising disease control approach in managing papaya dieback disease in Malaysia.

The Potential of Endophytic Fungi for Enhancing the Growth and Accumulation of Phenolic Compounds and Anthocyanin in Maled Phai Rice (Oryza sativa L.).

Rice (Oryza sativa L.) is one of the most popular cereal crops, being consumed by almost half of the world's population. Among several cultivars widely distributed in Thailand, Maled Phai is a Thai pigmented-upland rice with exceptionally high nutritional value and high demand in the local Thai market. This study aimed to investigate the feasibility of producing plant growth-promoting properties (PGP) and enhancing the accumulation of phytochemicals in Maled Phai rice seeds of endophytic fungi isolated from upland black rice. Among a total of 56 isolates, the 4 most effective PGP isolates were identified as Trichoderma zelobreve PBMP16, Talaromyces pinophilus PBMP28, Aspergillus flavus KKMP34, and Trichoderma sp. PBMP4 based on their morphological characteristics and multigene (ITS, rpb2, tef-1, CaM, and BenA) phylogenetic analyses. These four endophytic fungi could promote plant growth parameters under greenhouse conditions. Outstandingly, upland rice inoculated with Tr. zelobreve PBMP16 had a significant increase in total seed weight, root length, phenolic compounds, anthocyanin, antioxidants, and N uptake, which were higher than those of the noninoculated control, and even better than the chemical fertilizer. Overall, this report shows that endophytic fungi efficiently promoted growth and increased the phenolic compounds, anthocyanin, and antioxidants of Maled Phai rice.

Draft genome sequence of a halotolerant plant growth-promoting bacterium Pseudarthrobacter oxydans NCCP-2145 isolated from rhizospheric soil of mangrove plant Avicennia marina

BackgroundLimited knowledge exists regarding the diversity of mangrove plant-associated Pseudarthrobacter species. This study presents the first draft genome and phylogenetic analysis of a Pseudarthrobacter oxydans NCCP-2145, isolated from the rhizospheric soil of Aviciana marina, a native mangrove plant found in Miani Hor, Lasbela-Baluchistan, Pakistan. ResultsThe genome of P. oxydans NCCP-2145 comprises 4,495,869 base pairs, with a G+C content of 65.9% and 4,207 coding sequences. Genome annotation revealed the presence of multiple biosynthesis pathways. The analysis also identified genes responsible for plant growth-promoting traits, such as the synthesis of indole acetic acid, nitrogen fixation, and phosphorus solubilization. Experimental evaluations confirmed strain NCCP-2145 positive reactions for phosphorus solubilization, indole-3-acetic acid production, and ammonia production. Furthermore, strain NCCP-2145 exhibited tolerance to heavy metals (nickel, copper, and cadmium) and salinity levels up to 10% NaCl. Antibiotic susceptibility testing indicated resistance only to ceftazidime and the combination of amoxicillin/clavulanic acid. For phylogenomic analysis, strain NCCP-2145 was analyzed and compared to the closely related validly published type species P. oxydans DSM 20119T, revealing a similarity score of 98.64% based on 16S rRNA gene sequences and 89.1% based on DNA-DNA hybridization, confirming its classification as a member of species, P. oxydans. ConclusionsThis study significantly contributes to our understanding of the genomic characteristics, functional capabilities, and potential plant growth-promoting attributes of P. oxydans NCCP-2145. Future research should focus on unraveling the precise mechanisms underlying its plant growth-promoting abilities and exploring practical applications in sustainable agriculture and environmental restoration.How to cite: Bushra R, Uzair B, Ali A, et al. Draft genome sequence of a halotolerant plant growth-promoting bacterium Pseudarthrobacter oxydans NCCP-2145 isolated from rhizospheric soil of mangrove plant Avicennia marina. Electron J Biotechnol 2023;66. https://doi.org/10.1016/j.ejbt.2023.08.003.

Effectiveness of Phosphate and Zinc Solubilizing Paenarthrobacter nitroguajacolicus P1 as Halotolerant Rhizobacterium with Growth-Promoting Activity on Pistacia vera L.

Plant growth-promoting rhizobacteria (PGPR) are beneficial microorganisms to develop microbial fertilizers. Biofertilizers can accelerate plant growth and enhance crop yields. The current research aimed to isolate and identify rhizobacterium with plant growth-promoting activity in the rhizospheric region of pistachio trees in arid and salty region of Iran. In the present study, 26 bacterial isolates were isolated from the rhizospheric region of the pistachio trees. Plant growth-promoting characteristics of isolated bacteria, including the ability to solubilize phosphate and zinc, produce hydrolyzing enzymes, and hydrogen cyanide (HCN), as well as synthesize indole-3-acetic acid (IAA) were evaluated through in vitro assays. Based on these activities, five multifunctional bacterial strains designated P1, P10, P11, P17, and P19 were then applied and their effect was studied on the growth and physiological properties of Pistacia vera L. seedlings by pot experiments under normal conditions. Finally, the most efficient strain has been identified by analysis of the 16S rRNA gene sequence. According to the results, all the isolated bacteria exhibited considerable plant growth-promoting properties. They could produce amylase (n = 26, 2 ± 0.00-13 ± 0.42mm), lipase (n = 24, 2 ± 0.00-9 ± 0.23 mm), protease (n = 20, 1 ± 0.00-17 ± 0.0 mm), indole-3-acetic acid (n = 26, ranging from 5.05 ± 0.08 to 11.5 ± 0.11 μg/mL) and HCN (n = 24). Six isolates showed significant growth at 20% w/v NaCl. Inoculation of P1, P17, and P19 increased chlorophyll, carotenoid, and phenolic content in treated Pistacia vera L. seedlings. P1 and P11 inoculated plants showed an enhanced level of anthocyanin and proline. These most effective strains were catalase and Gram-positive bacterium and showed antibiotic sensitivity. They can consider as halotolerant PGPR, due to the growth in the presence of NaCl (20% w/v). Finally, P1 inoculated plants exhibited higher levels of sugar content. This strain showed the most similarity (99.92%-1322 bp) to Paenarthrobacter nitroguajacolicus based on 16S rRNA gene sequence. Based on the results, Paenarthrobacter nitroguajacolicus P1 with multiple PGPR can be applied as a promising candidate in the soil-Pistacia vera L. system to improve their productivity and health by increasing available nutrient content, improving photosynthetic parameters, and producing phytohormones and HCN.

Exploring the Potential of Bacillus velezensis, an Endophytic Bacteria Isolated from Alternanthera philoxeroides for Plant Growth Promotion and Bioremediation Properties

The current work was done to analyse the bioremediation and plant growth promotion (PGP) traits of endophytic bacteria isolated from Alternanthera philoxeroides from Bellandur Lake, Bangalore, India. Twenty-nine endophytic bacteria were isolated and tested for their PGP traits like indole acetic acid (IAA), ammonia, nitrogen fixation, 1-aminocyclopropane-1- carboxylate (ACC) deaminase production, phosphate solubilization etc. Endophytic bacterium, BEBAphL1 obtained from leaves of A. philoxeroides exhibited significant plant growth promotion properties and the isolate was identified as Bacillus velezensis OQ874364 using 16S rRNA sequencing. The bacterium showed potential IAA, ammonia production, nitrogen fixation, phosphate solubilization, and ACC deaminase production. The results indicate that this endophyte is promising as a growth-promoting inoculant, reducing the reliance on chemical inputs in conventional agricultural practices while enhancing nutrient uptake and stress resilience in plants. B. velezensis exhibited tolerance to high levels of chromium (500 mg/L) and NaCl (15%) and was also able to decolourize Congo red by 70% at 0.005% concentration of dye. Characterization of dye samples pre- and post-bacterial treatment was done using Fourier-transform infrared spectroscopy (FTIR) and Gas Chromatography-Mass Spectrometry (GC-MS) analysis. The findings of the study indicate that B. velezensis shows promise as a plant growth stimulator capable of withstanding heavy metal exposure and breaking down dyes.

Characterization of plant growth-promoting, antifungal, and enzymatic properties of beneficial bacterial strains associated with pulses rhizosphere from Bundelkhand region of India.

The present study was conducted to characterize the native plant growth-promoting rhizobacteria (PGPRs) from the pulse rhizosphere of the Bundelkhand region of India. Twenty-four bacterial isolates belonging to nineteen species (B.amyloliquefaciens, B. subtilis, B. tequilensis, B. safensis, B. haynesii, E. soli, E. cloacae, A. calcoaceticus, B. valezensis, S. macrescens, P. aeruginosa, P. fluorescens, P. guariconensis, B.megaterium, C. lapagei, P. putida, K. aerogenes, B. cereus, and B. altitudinis) were categorized and evaluated for their plant growth-promoting potential, antifungal properties, and enzymatic activities to identify the most potential strain for commercialization and wider application in pulse crops. Phylogenetic identification was done on the basis of 16s rRNA analysis. Among the 24 isolates, 12 bacterial strains were gram positive, and 12 were gram negative. Among the tested 24 isolates, IIPRAJCP-6 (Bacillusamyloliquefaciens), IIPRDSCP-1 (Bacillus subtilis), IIPRDSCP-10 (Bacillus tequilensis), IIPRRLUCP-5 (Bacillus safensis), IIPRCDCP-2 (Bacillus subtilis), IIPRAMCP-1 (Bacillus safensis), IIPRMKCP-10 (Bacillus haynesii), IIPRANPP-3 (Bacillusamyloliquefaciens), IIPRKAPP-5 (Enterobacter soli), IIPRAJCP-2 (Enterobacter cloacae), IIPRDSCP-11 (Acinetobacter calcoaceticus), IIPRDSCP-9 (Bacillus valezensis), IIPRMKCP-3 (Seratia macrescens), IIPRMKCP-1 (Pseudomonas aeruginosa), IIPRCKPP-3 (Pseudomonas fluorescens), IIPRMKCP-9 (Pseudomonas guariconensis), IIPRMKCP-8 (Bacillus megatirium), IIPRMWCP-9 (Cedecea lapagei), IIPRKUCP-10 (Pseudomonas putida), IIPRAMCP-4 (Klebsiella aerogenes), IIPRCKPP-7 (Enterobacter cloacae), IIPRAMCP-5 (Bacillus cereus), IIPRSHEP-6 (Bacillus subtilis), IIPRRSBa89 (Bacillus altitudinis) bacterial isolates, IIPRMKCP-9, IIPRAJCP-6, IIPRMKCP-10, IIPRAMCP-5, IIPRSHEP-6, and IIPRMKCP-3 showed the maximum antagonistic activity against Fusarium oxysporum f. sp. ciceris (FOC), Fusarium oxysporum f. sp. lentis (FOL), and Fusarium udum (FU) causing wilt disease of chickpea, lentil, and pigeonpea, respectively, and maximum plant growth-promoting enzyme (phosphatase), plant growth hormone (IAA), and siderophore production show promising results under greenhouse conditions. This study is the first report of bacterial diversity in the pulse-growing region of India.

Complete genome sequence of Pediococcus acidilactici A40, a bacterium with biocontrol and plant growth-promoting properties.

We report the complete genome assembly of Pediococcus acidilactici A40, a bacterium with biocontrol and plant growth-promoting properties, obtained from Colombia.

Plant growth-promoting properties of endophytic bacteria isolated from some xerophytic plants distributed in arid regions (Uzbekistan)

Recent advancements in the development of endophytic microorganisms-based stimulants have shown promising potential in various fields. Research on the identification of these endophytic microorganisms has been well reported, however, there are limited studies of these endophytes isolated from plants in arid regions. Thus, isolation and identification of promising microbial endophytes from xerophytic plants is essential in technology development for sustainable agriculture in arid regions. This study aims to identify the endophytic bacteria isolated from Kochia prostrata (L.) Schrad. and Ceratoides eversmanniana (Stschegl. ex I.G.Borshch.) Botsch. & Ikonn. in vertical zones of arid regions of Uzbekistan, and examine their potential plant growth-promoting properties. Using Luria-Bertani (LB) medium, 70 distinct bacterial colony were isolated from the different segments of K. prostrata and C. eversmanniana. These isotypes were screened using NaCl-supplemented LB medium in which nine promising bacterial isolates showed tolerance to 15% NaCl. The nine promising halophytes were subjected to molecular identification using specific primers. The isolates from K. prostrata are identified as Bacillus amyloliquefaciens, Bacillus pumilus, Priestia aryabhattai, Pseudomonas putida, and Priestia endophytica. On the other hand, Priestia megaterium, Pseudomonas putida, Bacillus subtilis and Brevibacillus parabrevis were isolated from C. eversmanniana. The identified isolates also showed significant plant growth-promoting properties (N2-fixation, IAA production, phosphates solubilization, ACC deaminase production, siderophores production) and shows ability to inhibit pathogenic fungal growth. Based on the result, the identified bacterial endophytes can be processed as growth-stimulants and biological control of fungal pathogens in crops in arid regions.

Impacts of rhizoremediation and biostimulation on soil microbial community, for enhanced degradation of petroleum hydrocarbons in crude oil-contaminated agricultural soils.

Hydrocarbonoclastic bacterial strains were isolated from rhizosphere of plants growing in crude oil-contaminated sites of Assam, India. These bacteria showed plant growth-promoting attributes, even when exposed to crude oil. Two independent pot trials were conducted to test the rhizodegradation ability of the bacterial consortium in combination of plants Azadirchta indica or Delonix regia in crude oil-contaminated soil. Field experiments were conducted at two crude oil-contaminated agricultural field at Assam (India), where plants (A. indica or D. regia) were grown with the selected bacterial consortium consisting of five hydrocarbonoclastic bacterial isolates (Gordonia amicalis BB-DAC, Pseudomonas aeruginosa BB-BE3, P. citronellolis BB-NA1, Rhodococcus ruber BB-VND, and Ochrobactrum anthropi BB-NM2), and NPK was added to the soil for biostimulation. The bacterial consortium-NPK biostimulation led to change in rhizosphere microbiome with enhanced degradation of petroleum hydrocarbons (PHs) in soils contaminated with crude oil. After 120 days of planting A. indica + consortium + NPK treatment, degradation of PHs was found to be up to 67%, which was 55% with D. regia with the same treatment. Significant changes in the activities of plant and soil enzymes were also noted. The shift is bacterial community was also apparent as with A. indica, the relative abundance of Proteobacteria, Actinobacteria, and Acidobacteria increased by 35.35%, 26.59%, and 20.98%, respectively. In the case of D. regia, the relative abundance of Proteobacteria, Actinobacteria, and Acidobacteria were increased by 39.28%, 35.79%, and 9.60%, respectively. The predicted gene functions shifted in favor of the breakdown of xenobiotic compounds. This study suggests that a combination of plant-bacterial consortium and NPK biostimulation could be a productive approach to bioengineering the rhizosphere microbiome for the purpose of commercial bioremediation of crude oil-contaminated sites, which is a major environmental issue faced globally.

Screening of endophytic Bacteria from stress-tolerating plants for abiotic stress tolerance and plant growth-promoting properties: Identification of potential strains for bioremediation and crop enhancement

Enhancing plant productivity and fortifying defense mechanisms against biotic and abiotic stresses is crucial for sustainable agriculture. To achieve this, researchers have investigated the use of endophytic bacteria as a viable alternative to chemical fertilizers and pesticides. In this study, 50 endophytic microbes were isolated from stress-tolerant parts of different plants, including Lantana camara, Phoenix dactylifera, Hemerocallis fulva, Salvia rosmarinus, Commiphora wightii, and Abutilon indicum. These microbes were evaluated for their tolerance to abiotic stresses and ability to promote plant growth. Among the isolates, R1L2 and A2L2L2 exhibited the highest tolerance to salt stress, withstanding up to 16% NaCl. DL2R2, R1L2, and A1S1S were the most tolerant to lead stress, tolerating up to 6% w/v lead. For cadmium stress, R1L2, DL3R2, and DP1L1L1 showed the highest tolerance, enduring up to 6% w/v cadmium. The isolates were also assessed for their plant growth-promoting (PGP) activities, including the production of IAA, Gibberellin, Cytokinin, HCN, siderophore, phosphate solubilization, and nitrogen fixation. All isolates were positive for nitrogen fixation attribute. However, under specific stress conditions, all isolates showed negative results for HCN production, siderophore production, or inorganic phosphate solubilization. Isolates A1S1S and DL3R2 demonstrated positive results for producing phytohormones such as IAA, Gibberellin, and Cytokinin. Through phenotypic and biochemical characteristics, as well as 16S rDNA gene sequencing, isolate A1S1S was identified as Pelomonas aquatic (accession no. OP984335), and isolate DL3R2 was identified as Solibacillus silvestris (accession no. OP854919). These findings suggest that the endophytic strains Pelomonas aquatic and Solibacillus silvestris have potential applications as multi-stress reducers, bioremediation agents, and crop growth promoters in essential crops.

Isolation of bacteria with plant growth-promoting properties from microalgae-bacterial flocs produced in high-rate oxidation ponds

ABSTRACT Exploring plant growth-promoting (PGP) bacterial activity of microbial components aggregated by wastewater treatment can reduce dependence on fossil fuel-derived fertilisers. This study describes the isolation and identification of bacteria from microalgae-bacteria flocs (MaB-flocs) generated in high-rate algal oxidation ponds (HRAOP) of an integrated algal pond system (IAPS) remediating municipal wastewater. Amplified 16S rRNA gene sequence analysis determined the molecular identity of the individual strains. Genetic relatedness to known PGP rhizobacteria in the NCBI GenBank database was by metagenomics. Isolated strains were screened for the production of indoles (measured as indole-3-acetic acid; IAA) and an ability to mineralise NH 4 + , PO 4 3 − , and K + . Of the twelve bacterial strains isolated from HRAOP MaB-flocs, four produced indoles, nine mineralised NH 4 + , seven solubilised P, and one K. Potential of isolated strains for PGP activity according to one-way ANOVA on ranks was: ECCN 7b > ECCN 4b > ECCN 6b > ECCN 3b = ECCN 10b > ECCN 1b = ECCN 5b > ECCN 8b > ECCN 2b > ECCN 12b > ECCN 9b = ECCN 11b. Further study revealed that cell-free filtrate from indole-producing cultures of Aeromonas strain ECCN 4b, Enterobacter strain ECCN 7b, and Arthrobacter strain ECCN 6b promoted mung bean adventitious root formation suggestive of the presence of auxin-like biological activity.