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The present work was focused on plant growth-promoting bacteria (PGPB) for the enhanced production of tomatoes. The effect of 14 indigenous PGPB isolated from the soil samples collected from Gir National forest areas (Dist. Junagadh, Gujarat, India) and the coastal region of Saurashtra (Dist. Gir-Somnath, Gujarat, India) on tomato seedlings was studied. Only 6 isolates showed positive results in in vitro biochemical and plant-growth-promoting assays such as phosphate and zinc solubilization, siderophores and HCN production and antibacterial and antifungal properties. The rest isolates were negative to one or more of the selected tests. Based on in vitro results, all PGPB were tested on tomato seedlings. Four stage screenings were used to select the best combinations. After the primary screening, 9 isolates were selected for further experiments based on the germination, height of plants and seedling vigor. Plant height, leaf count, seedling vigor and total chlorophyll were measured. Leaf anatomy was studied at the end of the quaternary trial to understand the changes at a cellular level and it revealed the anatomical changes such as increased chlorophyll at cellular level and enhanced starch production. Microbial consortia showed better results compated to single-inoculant treatment. Out of 503 different combinations tested at secondary trial, 129 were selected for tertiary trials and 24 from them were further qualified for quaternary trials. At the end of quaternary trials, total 04 combinations were selected for future experiments on field. The quaternary trial strategy helped to reduce the total 503 possible combinations to 04 combinations improving germination, height, seedling vigor, number of leaves and chlorophyll content compared to non-treated tomato plants. Further trials were carried out in field for long period of time to measure the profound effect of selected consortium in real life. [ABSTRACT FROM AUTHOR]

Siderophores are low molecular weight iron scavengers produced by bacteria to combat iron stress and also suppress deleterious rhizobacteria. In the present study, microbes were isolated from wheat and tobacco farm in Changa village, Anand district, India, and were screened for their siderophore production. Out of 11 isolates, 6 were siderophore producers as they produced orange halos on CAS agar. Isolated bacteria were examined for their hydroxamate, catechol, and carboxylate type of siderophore, and it revealed that all produced hydroxamate siderophore. Among all the isolates, a potential bacterium was selected for further studies and identified by the biochemical test as Pseudomonas sp. MT. Temporal effect on growth and siderophore production revealed that both were higher at 24 hrs of incubation and remained active up to 8 days and then after the decline. Siderophore was partially purified and chemically characterized by FTIR. A particle size analyzer measured the particle size of the siderophore and showed 91.36 nm in size. The siderophore producer and non-producer were examined for their ability to uptake iron by providing external siderophores, which gave positive results. The isolated bacterium was tested for its antagonistic activity against Fusarium oxysporum f. sp. cubense and F. oxysporium f. sp. ciceris, resulting in inhibition of both the species. Hence, Pseudomonas sp. MT can be effectively used to control Fusarium spp. [ABSTRACT FROM AUTHOR]

Microorganisms produce siderophores, which are low-molecular-weight iron chelators when iron availability is limited. The present analyzed the role of LNPF1 as multifarious PGPR for improving growth parameters and nutrient content in peanut and soil nutrients. Such multifarious PGPR strains can be used as effective bioinoculants for peanut farming. In this work, rhizosphere bacteria from Zea mays and Arachis hypogaea plants in the Salem area of Tamil Nadu, India, were isolated and tested for biochemical attributes and characteristics that stimulate plant growth, such as the production of hydrogen cyanide, ammonia (6 µg/mL), indole acetic acid (76.35 µg/mL), and solubilizing phosphate (520 µg/mL). The 16S rRNA gene sequences identified the isolate LNPF1 as Pseudomonas fluorescens with a similarity percentage of 99% with Pseudomonas sp. Isolate LNPF1 was evaluated for the production of siderophore. Siderophore-rich supernatant using a Sep Pack C18 column and Amberlite-400 Resin Column (λmax 264) produced 298 mg/L and 50 mg/L of siderophore, respectively. The characterization of purified siderophore by TLC, HPLC, FTIR, and 2D-NMR analysis identified the compound as desferrioxamine, a hydroxamate siderophore. A pot culture experiment determined the potential of LNPF1 to improve iron and oil content and photosynthetic pigments in Arachis hypogaea L. and improve soil nutrient content. Inoculation of A. hypogea seeds with LNPF1 improved plant growth parameters such as leaf length (60%), shoot length (22%), root length (54.68%), fresh weight (47.28%), dry weight (37%), and number of nuts (66.66) compared to the control (untreated seeds). This inoculation also improved leaf iron content (43.42), short iron content (38.38%), seed iron (46.72%), seed oil (31.68%), carotenoid (64.40%), and total chlorophyll content (98.%) compared to control (untreated seeds). Bacterized seeds showed a substantial increase in nodulation (61.65%) and weight of individual nodules (95.97) vis-à-vis control. The results of the present study indicated that P. fluorescens might be utilized as a potential bioinoculant to improve growth, iron content, oil content, number of nuts and nodules of Arachishypogaea L., and enrich soil nutrients., (© 2024. The Author(s).)

Mangroves are unique ecosystems in the coastal tropical and subtropical regions of the Earth. The fluctuation in salinity due to tidal action results in a prolific population of adhered halophilic and halotolerant bacteria in this ecosystem. In this study, a pigment producing adhered bacterial strain Halobacillus trueperi MXM-16 was isolated from mangrove plant litter of Goa. This strain was moderately halophilic, Gram positive rod, catalase positive and capable of utilizing sodium benzoate as a source of carbon. H. trueperi MXM-16, produced a siderophore that was hydroxamate in nature. The non-diffusible yellow pigment was a carotenoid and HPLC studies revealed a peak that was indicative of astaxanthin as one of the component. Further studies on the pigment exhibited its ability to chelate iron from the chrome azurol sulphonate medium behaving as an additional mechanism for iron acquisition. [ABSTRACT FROM AUTHOR]

The most effective agricultural practice to prevent iron deficiency in calcareous soils is fertilizing with synthetic chelates. These compounds are non-biodegradable, and persistent in the environment; hence, there is a risk of leaching metals into the soil horizon. To tackle iron deficiency-induced chlorosis (IDC) in crops grown on calcareous soils, environmentally friendly solutions are needed rather than chemical application as it affects the soil health further. Hence, the present work focused on isolating and screening calcareous soil-specific bacteria capable of producing iron-chelating siderophores. Siderophore-producing bacteria (SPB) was isolated from the groundnut (Arachis hypogea L.) rhizosphere region, collected from Coimbatore district, Tamil Nadu, of which 17 bacterial isolates were positive for siderophore production assayed by chrome azurol sulphonate. The performance of SPB isolates was compared for siderophore kinetics, level of siderophore production, type of siderophore produced and iron-chelating capacity under 15 mM KHCO 3 . Four best performing isolates were screened, with average siderophores yield ranging ∼60-80% under pH 8, with sucrose as carbon source and NH 2 SO 4 as nitrogen source at 37 °C. The four efficient SPB were molecularly identified as B. licheniformis, B. subtilis, B. licheniformis, and O. grignonense based on 16S rDNA sequencing. The simultaneous inhibition method showed T.viride has the highest antagonistic effect against S.rolfsii, and M.phaseolina with a reduction of mycelial growth by 69.3 and 65.1%, respectively, compared to control. Our results indicate that the optimized conditions enhanced siderophores chelation by suppressing the stem and root rot fungi, which could help in a cost-effective and environmentally friendly manner., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Chromium-resistant plant growth-promoting bacteria (PGPB) were isolated from the electroplating industry waste disposal site soils at Coimbatore, India, using LB medium. The strain tolerated chromium concentrations up to 500 mg Cr6+L−1on LB medium. The strain was identified as Pseudomonas sp. VRK3 based on its morphological, physiological, and biochemical characteristics following Bergey's manual of determinative bacteriology. Evaluation of plant growth-promoting parameters revealed the intrinsic ability of the strain for the production of indole-3-acetic acid (IAA), siderophore, and solubilization of insoluble phosphate. Pseudomonas sp. VRK3 utilized tryptophan as a precursor for the growth and production of IAA (105.77 μg mL−1) and also exhibited the production of siderophore. The strain utilized tricalcium phosphate as the sole source of phosphate exhibiting a high rate of phosphate solubilization (0.49 μg mL−1). Pseudomonas sp. VRK3 showed a significant extent of chromium uptake and accumulation in their cell walls. Furthermore, Pseudomonas sp. VRK3 was demonstrated to possess mobilization of chromium from the soil that would enhance chromium availability to the plant. Potential use of this Pseudomonas sp. VRK3 as PGPB needs further testing in enhancing the growth and chromium uptake by the plants in pots under nursery conditions. [ABSTRACT FROM AUTHOR]

Sixty-four arsenic (As) resistant bacteria isolated from an arsenic rich groundwater sample of West Bengal were characterized to investigate their potential role in subsurface arsenic mobilization. Among the isolated strains predominance of genera Agrobacterium/Rhizobium, Ochrobactrum and Achromobacter which could grow chemolitrophically and utilize arsenic as electron donor were detected. Higher tolerance to As [maximum tolerable concentration (MTC): ≥10 mM], As (MTC: ≥100 mM) and other heavy metals like Cu, Cr, Ni etc. (MTC: ≥10 mM), presence of arsenate reductase and siderophore was frequently observed among the isolates. Ability to produce arsenite oxidase and phosphatase enzyme was detected in 50 and 34 % of the isolates, respectively. Although no direct correlation among taxonomic identity of bacterial strains and their metabolic abilities as mentioned above was apparent, several isolates affiliated to genera Ochrobactrum, Achromobacter and unclassified Rhizobiaceae members were found to be highly resistant to As and As and positive for all the test properties. Arsenate reductase activity was found to be conferred by arsC gene, which in many strains was coupled with arsenite efflux gene arsB as well. Phylogenetic incongruence between the 16S rRNA and ars genes lineages indicated possible incidence of horizontal gene transfer for ars genes. Based on the results we propose that under the prevailing low nutrient condition inhabitant bacteria capable of using inorganic electron donors play a synergistic role wherein siderophores and phosphatase activities facilitate the release of sediment bound As, which is subsequently reduced by arsenate reductase resulting into the mobilization of As in groundwater. [ABSTRACT FROM AUTHOR]

In this study, Arthrobacter luteolus, isolated from rare earth environment of Chavara (Quilon district, Kerala, India), were found to produce catechol-type siderophores. The bacterial strain accumulated rare earth elements such as samarium and scandium. The siderophores may play a role in the accumulation of rare earth elements. Catecholate siderophore and low-molecular-weight organic acids were found to be present in experiments with Arthrobacter luteolus. The influence of siderophore on the accumulation of rare earth elements by bacteria has been extensively discussed. [ABSTRACT FROM AUTHOR]

Tributyltin (TBT) is a very effective biocide and an active ingredient in antifouling paints. Screening along the Indian coast yielded 49 bacterial isolates capable of TBT assimilation. The screening was done based on the ability of bacteria to grow in mineral salt medium (MSM) containing TBT as the sole source of carbon. All the isolates produced exopolysaccharides (biosurfactants) in the medium which aid in emulsification and thus ease bioavailability of TBT. Five isolates were identified as potent TBT degraders (namely, Pseudomonas pseudoalcaligenes, Pseudomonas stutzeri, Pseudomonas mendocina, Pseudomonas putida, and Pseudomonas balearica) based on their biomass production in MSM containing TBT as the sole source of carbon. In addition to evaluating the potential of individual bacterial strains, the study also focused on using a consortium of bacteria to explore their synergistic effect when grown on TBT. Further tests like growth profile, rhamnolipid secretion profile, extracellular protein secretion profile, and detection of siderophores were performed on these isolates when grown in MSM supplemented with 2 mM TBT concentration. Emulsification activity of the crude extracellular polysaccharides against kerosene was evaluated. It can be therefore inferred that TBT degradation by these marine pseudomonads is a two-step process: (a) dispersion of TBT in the aqueous phase and (b) tin-carbon bond cleavage by siderophores affecting debutylation of TBT. The consortium of bacteria may be effective in the treatment of TBT-contaminated waste water in dry docks. [ABSTRACT FROM AUTHOR]

In this study, a total of 80 rhizobacteria was isolated from coastal agricultural ecosystem of cultivated vegetable rhizosphere soils. The isolates were screened for antagonistic activity against Sclerotium rolfsii and Colletotrichum capsici and plant growth promoting traits. The results revealed that 15.0 and 43.7% isolates showed statistically significant inhibition of mycelial growth of S. rolfsii and C. capsici respectively, while 48.7% isolates produced siderophore, 57.5% isolates solubilized phosphate and 21.1% isolates produced indole-3-acetic acid more than 20 μg/mL. However, only three isolates PfS1, PfR2 and BL5 were found positive to all properties tested. The identification of potential bacterial isolates through Microbial Identification System (BIOLOG) and 16S rDNA sequencing of the isolates revealed Bacillus species were dominant in the cultivated vegetable rhizosphere soil of Neil and Havelock Islands, India. [ABSTRACT FROM AUTHOR]

lead-resistant bacterial strain 4EA from soil contaminated with car battery waste from Goa, India was isolated and identified as Pseudomonas aeruginosa. This lead-resistant bacterial isolate interestingly revealed lead-enhanced siderophore (pyochelin and pyoverdine) production up to 0.5 mM lead nitrate whereas cells exhibit a significant decline in siderophore production above 0.5 mM lead nitrate. The bacterial cells also revealed significant alteration in cell morphology as size reduction when exposed to 0.8 mM lead nitrate. Enhanced production of siderophore was evidently detected by chrome azurol S agar diffusion (CASAD) assay as increase in diameter of orange halo, and reduction in bacterial size along with significant biosorption of lead was recorded by scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX). Pseudomonas aeruginosa strain 4EA also exhibits cross tolerance to other toxic metals viz. cadmium, mercury, and zinc besides resistance to multiple antibiotics such as ampicillin, erythromycin, amikacin, cephalexin, co-trimoxazole, mecillinam, lincomycin, ciphaloridine, oleondamycin, and nalidixic acid. [ABSTRACT FROM AUTHOR]

Twenty-five fluorescent pseudomonads from rhizospheric soil of six tea gardens in four district of Upper Assam, India were isolated and screened for antagonistic activity against fungal pathogens such as Fusarium oxysporum f. sp. raphani (For) , Fusarium oxysporum f. sp . ciceri (Foc) , Fusarium semitectum (Fs), and Rhizoctonia solani (Rs); and bacterial pathogens- Staphylococcus aureus (Sa) , Escherichia coli (Ec), and Klebsiella pneumoniae (Kp). Most of the isolates exhibited strong antagonistic activity against the fungal pathogens and gram-positive bacterium i.e. Staphylococcus aureus. Productions of siderophore, salicylic acid (SA), hydrogen cyanide (HCN), and cell wall-degrading enzyme (chitinase) were studied to observe the possible mechanisms of antagonistic activity of the isolates. Correlation between the antagonistic potentiality of some isolates and their levels of production of siderophore, salicylic acid, and hydrogen cyanide was observed. Out of the 25 isolates, antibiotic-coding genes, 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT) were detected in the isolates, Pf12 and Pf373, respectively . Genetic diversity of these fluorescent pseudomonads were analyzed with reference to four strains of Pseudomonas fluorescens NICM 2099, P. aeruginosa MTCC 2582, P. aureofaciens NICM 2026, and P. syringae MTCC 673. 16S rDNA-RFLP analysis of these isolates using three tetra cutter restriction enzymes ( HaeIII, AluI and MspI) revealed two distinct clusters. Cluster A comprised only two isolates Pf141 and 24-PfM3, and cluster B comprised 23 isolates along with four reference strains. [ABSTRACT FROM AUTHOR]

Gram-positive rod-shaped bacterium isolated on nutrient agar plates incubated at 28 ± 2°C. The identity of the bacterium was confirmed by sequencing of the 16S rRNA gene and it reveals that it shares highest similarity with Bacillus thioparus CECT 7196 (99.08%). It was capable of growing at temperatures ranging from 4 to 40°C, but optimum growth was observed at 28 ± 2°C. Strain NII-0902 is endowed with multiple plant growth promotion attributes such as phosphate solubilization, Indole acetic acid (IAA), siderophore and HCN production, which were expressed differentially at sub-optimal temperatures (5-40°C). It was able to solubilize phosphate (17.7 μg ml), and produce IAA (139.7 μg ml) at 28 ± 2°C. Qualitative detection of siderophore production and HCN were also observed. At 5°C it was found to express all the plant growth promotion attributes except HCN production. The ability to colonize roots is a sine qua non condition for a rhizobacteria to be considered a true plant growth-promoting rhizobacteria (PGPR). Bacillus sp. NII-0902 has a potential ability to colonize roots visualized by transparency, bacterial growth (turbid, milky and narrow zone) along and around roots and truly supported by scanning electron micrograph. Hence, it is proposed that, Bacillus thioparus sp. NII-0902 could be deployed as an inoculant to attain the desired results of bacterization. [ABSTRACT FROM AUTHOR]

Abstract   Exiguobacterium acetylicum strain 1P (MTCC 8707) is a rhizospheric, Gram positive, rod shaped, yellow pigmented bacterium isolated from an apple orchard rhizospheric soil, on nutrient agar plates incubated at 4°C. The species level identification was arrived on the basis of 16S rRNA gene sequencing. The sequence showed 98% similarity with sequences of E. acetylicum available in the public domain. The strain was positive for siderophore and HCN production. In separate invitro assays it was found to inhibit the growth and development of Rhizoctonia solani, Sclerotium rolfsii, Pythium and Fusarium oxysporum. The volatile compound produced by the bacterium was found to be the most potent in inhibiting the hyphal development of R. solani, S. rolfsii, Pythium and F. oxysporum by 45.55, 41.38, 28.92 and 39.74% respectively. Commonly observed deformities caused by the diffusible and volatile compounds produced by the bacterium included hyphal inhibition, constriction and deformation. Under pot culture conditions the bacterium improved the germination and early growth parameters of pea (Pisum sativum) in the presence of R. solani and S. rolfsii. [ABSTRACT FROM AUTHOR]

An arsenic resistant bacteria SMSKVR-3 has been isolated from the rhizospheric soil of the metal-contaminated site of khetri copper mines situated in the Jhunjhunu district of Rajasthan, India. The strain showed homology with Pseudomonas mendocina strain ATCC 25411. This gram-negative isolate exhibited optimal growth in M9 minimal media with temperature and salt concentration as 30 °C and 0.25% (w/v), respectively, at pH 7.0. The similar growth pattern and SEM analysis of this strain exposed to M9 minimal media alone, M9 media supplemented with 300 mM arsenate [As(V)] or M9 media supplemented with 1.34 mM arsenite [As(III)] indicate the existence of the strong arsenic resistance mechanism. The isolate was able to produce siderophores and was able to reduce As(V) to As(III). A decrease in polyP concentration from 354.8 µg/10 10  CFU mL -1 at 0 h to 0.043 µg/10 10  CFU mL -1 at 8 h incubation with As(V) was in correlation with the change in intracellular As(V) concentration (116.98 mg L -1 /10 10 cells at 0 h to 88.65 mg L -1 /10 10 at 8 h) with time. This shows the possible role of polyP bodies in the regulation of As(V) concentration inside the cell. The presence of arsC gene in P.mendocina SMSKVR-3 was confirmed by the PCR amplification of arsC gene. The BLAST analysis of the sequenced gene represented 98.59% identity with the P. mendocina S5.2 arsenate reductase. These results indicate that the observed arsenic resistance in SMSKVR-3 is due to a combination of siderophore production, the transformation of As(V) to As(III) by arsenate reductase, multi-drug efflux pump, and polyP bodies mediated metal resistance mechanism., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Iron (Fe) is one of the essential micronutrients for all living organisms. Despite its abundance in most of the contaminated soil, it is usually in unavailable forms. The unavailable form of Fe could be mobilized to plants by the use of microorganisms. This study was carried out to show that the Fe-contaminated field soils could be used to accumulate Fe in the plant parts using bacterial inoculation. For this, from a set of bacterial isolates, four Fe-tolerant bacteria were selected and identified based on 16S rRNA gene sequencing. The Fe-tolerant bacteria belonged to the genus Bacillus toyonensis (MG430287), Rhodococcus hoagii (MG432495), Lysinibacillus mangiferihumi (MG432492), and Lysinibacillus fusiformis (MG430290). Screening of plant growth-promoting properties of these isolates revealed that all isolates were able to produce indole acetic acid (50.0-84.0 μg/ml), siderophore, and potassium solubilization (except R. hoagii). Pot assay using Fe-contaminated ((8.07-8.35 g kg -1 ) soils River Directorate of India) revealed that Fe-tolerant bacteria enhanced the growth of Brassica juncea and its biomass. Besides the improved plant growth, the inoculated plants also showed an overall percentage increase in the uptake of iron in root, stem, and leaf (57.91-128.31%) compared with uninoculated plants. In addition to enhanced plant growth attributes, the isolates also improved the total chlorophyll content and antioxidant properties such as total phenol, proline, and ascorbic acid oxidase. Thus, the results clearly indicated that these isolates could be used as a bioinoculant to improve the sequestration of Fe from the contaminated soils and alleviation of Fe stress in plants.

The diversity of culturable Bacilli was investigated in six wheat cultivating agro-ecological zones of India viz: northern hills, north western plains, north eastern plains, central, peninsular, and southern hills. These agro-ecological regions are based on the climatic conditions such as pH, salinity, drought, and temperature. A total of 395 Bacilli were isolated by heat enrichment and different growth media. Amplified ribosomal DNA restriction analysis using three restriction enzymes AluI, MspI, and HaeIII led to the clustering of these isolates into 19-27 clusters in the different zones at >70% similarity index, adding up to 137 groups. Phylogenetic analysis based on 16S rRNA gene sequencing led to the identification of 55 distinct Bacilli that could be grouped in five families, Bacillaceae (68%), Paenibacillaceae (15%), Planococcaceae (8%), Staphylococcaceae (7%), and Bacillales incertae sedis (2%), which included eight genera namely Bacillus, Exiguobacterium, Lysinibacillus, Paenibacillus, Planococcus, Planomicrobium, Sporosarcina, and Staphylococcus. All 395 isolated Bacilli were screened for their plant growth promoting attributes, which included direct-plant growth promoting (solubilization of phosphorus, potassium, and zinc; production of phytohormones; 1-aminocyclopropane-1-carboxylate deaminase activity and nitrogen fixation), and indirect-plant growth promotion (antagonistic, production of lytic enzymes, siderophore, hydrogen cyanide, and ammonia). To our knowledge, this is the first report for the presence of Bacillus endophyticus, Paenibacillus xylanexedens, Planococcus citreus, Planomicrobium okeanokoites, Sporosarcina sp., and Staphylococcus succinus in wheat rhizosphere and exhibit multifunctional PGP attributes. These niche-specific and multifarious PGP Bacilli may serve as inoculants for crops growing in respective climatic conditions., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Transfusional iron overload associated with thalassemia leads to the appearance of non-transferrin-bound iron (NTBI) in blood that is toxic and causes morbidity and mortality via tissue damage. Hence, a highly sensitive and accurate assay of NTBI, with broad clinical application in both diagnosis and validation of treatment regimens for iron overload, is important. An assay based on iron chelation by a high-affinity siderophore, azotobactin, has been developed. The steps consist of blocking of native apotransferrin iron binding sites, mobilization of NTBI, ultrafiltration of all serum proteins, and finally the addition of the probe, which has a chromophore that fluoresces at 490 nm. Binding of Fe3+ to azotobactin quenches the fluorescence in a concentration-dependent manner. Measured NTBI levels in 63 sera ranged from 0.07 to 3.24 microM (0.375+/-0.028 microM [means+/-SEM]). It correlated well with serum iron and percentage transferrin saturation but not with serum ferritin. Pearson's correlation coefficients were found to be 0.6074 (P<0.0001) and 0.6102 (P<0.0001) for percentage transferrin saturation and total serum iron, respectively. The low values are due to the patients being under regular chelation therapy even prior to sampling, indicating that the method is sensitive to very low levels of NTBI, allowing a much lower detection limit than the available methods.