ECOTERRA - ECOTERRA Journal of Environmental Research and Protection Bioremediation of heavy metals (Zn and Cr) using microbial biosurfactant

Abstract. In the present study ten different strains of bacteria were isolated from the heavy metal contaminated soil and water. The isolated colonies were cultured on Blood-Agar plates and subjected to haemolysis. The strains showing α and β haemolysis were observed positive for biosurfactant production. These strains were characterized biochemically and morphologically. The morphological identification confirms that the isolates were Gram negative Bacilli. Further the production of biosurfactant was confirmed with the help of CTAB method which confirms the production of biosurfactant, rhamnolipid. The purified biosurfactant from isolate vb4 was studied for degradation of heavy metal i.e. Chromium and Zinc. The degradation was analysed on X-Ray fluorescence spectrophotometry. In the sample with Chromium conc. of 10 and 20 ppm, the metal was reduced to the concentration of 4.5 ppm and 9 ppm, respectively. While in the sample with chromium at 80 ppm, the remaining amount of heavy metal was 41 ppm. In case of Zinc, the 40 ppm sample was degradated upto 2 ppm and 80 ppm sample was degradated upto 26 ppm

Screening, isolation and characterization of culturable stress-tolerant bacterial endophytes associated with Salicornia brachiata and their effect on wheat (Triticum aestivum L.) and maize (Zea mays) growth

Globally more than 5.2 billion hectares of farming fields are damaged through erosion, salinity and soil deterioration. Many salt stress tolerant bacteria have plant growth promoting (PGP) characteristics that can be used to overcome environmental stresses. Isolation and screening of salt-tolerant endophytes from Salicornia brachiata were achieved through surface sterilization of leaves followed by cultivation on 4% NaCl amended media. Performance of isolates towards indole-3-acetic acid (IAA) production, phosphate solubilization, ACC deaminase activity, ammonia production, siderophore production and stress tolerance were determined. On the basis of the highest plant growth promoting activity, SbCT4 and SbCT7 isolates were tested for plant growth promotion with wheat and maize crops. In the present study, a total of 12 morphologically distinct salt-tolerant endophytic bacteria was cultured. Out of 12 isolates, 42% of salt-tolerant endophytes showed phosphate solubilization, 67% IAA production, 33% ACC-deaminase activity, 92% siderophore production, 41.6% ammonia production and 66% HCN production. A dendrogram, generated on the basis of stress tolerance, showed two clusters, each including five isolates. The bacterial isolates SbCT4 and SbCT7 showed the highest stress tolerance, and stood separately as an independent branch. Bacterial isolates increased wheat shoot and root dry weights by 60–82% and 50–100%, respectively. Similarly, improved results were obtained with maize shoot (27–150%) and root (80–126%) dry weights. For the first time from this plant the bacterial isolates were identified as Paenibacillus polymyxa SbCT4 and Bacillus subtilis SbCT7 based on phenotypic features and 16S rRNA gene sequencing. Paenibacillus polymyxa SbCT4 and B. subtilis SbCT7 significantly improved plant growth compared to non-inoculated trials

Screening and identification of abiotic stress-responsive efficient antifungal Pseudomonas spp. from rice rhizospheric soil

Plant growth-promoting rhizobacteria (PGPR) are a collection of microorganisms often used to support and promote plant development and combat plant infectious diseases with various biological control methods. The most significant restricting factors for agricultural productivity worldwide are abiotic constraints. In the present study, seven bacterial isolates from the rice rhizosphere were selected for detailed tests based on results obtained in experiments determining the ACC deaminase synthesis and drought tolerance at !0.30 MPa PEG level. Screening results of the stress tolerance analysis of the seven isolates for elevated temperature (50°C), alkalinity (10% NaCl), and drought (-1.2 MPa) showed that abiotic stress resistance was less prevalent in DRO2, DRO13, and DRO43 isolates than in DRO17, DRO28, DRO35, and DRO51 isolates. During the study, it was observed that DRO17, DRO28, and DRO51 tended to maintain similar cell density at -0.73 MPa PEG level, as observed at -0.30 MPa stress condition. No bacterial growth was observed at higher PEG level (-1.12 MPa) for any bacterial isolate. Four strains of Pseudomonas (DRO17, DRO28, DRO35, and DRO51) exhibited salinity and temperature tolerance. Antifungal screening using the bangle method showed that DRO35 was highly antagonistic towards Rhizoctonia solani 4633, followed by Fusarium moniliforme 4223, with an inhibition of 64.3% and 48%, respectively. The DRO28 isolate exhibited 72.5% growth inhibition for Fusarium moniliforme 4223, while the DRO51 isolate showed 38.2% growth inhibition for Bipolaris hawaiiensis 2445. DRO17 reduced the growth of Rhizoctonia solani 4633, and Curvularia lunata 350 by 36% and 31%, respectively. In conclusion, the screening of bacterial strains with promising stress tolerance and antifungal characteristics could support farmers to achieve the required positive outcomes in the agriculture field

Effect of halotolerant plant growth-promoting rhizobacteria from Bougainvillea glabra on wheat and maize seedlings under NaCl stress

Wheat and maize are the main staple food crops that contribute to human food security. Their growth, however, is reduced under stresses such as salinity. The plant microbiome is associated with each plant tissue and develops a holobiont in association with the plant. Plants actively manage the configuration of their related bacterial population and its function. These microorganisms provide a broad range of benefits and advantages to the plants. The present study aimed to examine the growth improvement of wheat var. HD 2687 and maize var. PSCL-4642 under salinity at the seedling stage following inoculation of salt-tolerant plant growth-promoting rhizobacteria (PGPR) BoGl120 purified from Bougainvillea glabra. The seed germination potential with/without bacterial inoculation was examined at 50, 100, 150, and 200 mM NaCl concentrations for both crops. Compared to controls, at 50 mM NaCl concentration, the BoGl120 isolate provided the maximum radicle length in maize (32 mm) and in wheat (24.8 mm). At 100 mM NaCl concentration, however, the radicle length of wheat and maize seedlings was decreased. Inoculation of plants with the BoGl120 isolate enhanced the plumule length of seedlings at different NaCl concentrations as compared to controls. In comparison with controls, BoGl120 improved the plumule length of wheat to 32.6, 14.0, and 8 mm at 50, 100, and 150 mM NaCl concentrations, respectively. The results of the present study support the concept that PGPRs could help to increase the tolerance against saline stress in wheat and maize at the seedling stage

Screening Of Plant Growth–Promoting Rhizobacteria From Maize ( Zea Mays ) And Wheat ( Triticum Aestivum )

Plant growth-promoting rhizobacteria (PGPR) are free-living soil-borne bacteria that colonize the rhizosphere and have great importance in governing the functional property of terrestrial ecosystems. In this study, rhizospheric bacteria were isolated from maize and wheat and screened for their plant growth promoting activities. These isolates were identified as Pseudomonas , Bacillus , Azospirillum and Azotobacter species. All isolates were tested for their indole acetic acid (IAA) production ability. All isolates produce the varying amounts of IAA ranging from 0.6-2.7 μg/ml. The highest concentration of IAA was produced by bacterial strain Bacillus subtilis AK31. A series of growth pouch and pot experiments were conducted to study the effect of bacterial inoculants on the growth of maize and wheat. It was concluded that IAA plays a key role in the growth promotion of roots in maize and wheat in growth pouch study. In maize, isolate AK1, AK21, AK31 and AK8 showed high indole acetic acid (6.86, 7.11, 7.11 and 7.36 pmol/ml, respectively) and root elongation activity (4.10, 5.00, 5.00 and 3.80 cm, respectively) after 96h of growth. In wheat, bacterial strains AK31, AK2, AK14, AK32 and AK15 showed high IAA (6.59, 5.66, 5.35, 7.53 and 5.66 pmol/ml, respectively) and root elongation (6.07, 4.00, 5.20, 6.90 and 5.20 cm, respectively) activity after 96h of growth. In pot experiments, Bacillus sp. AK21, Bacillus subtilis AK31, Azotobacter diazotrophicus AK14, Microbacterium sp. AK19 and Pseudomonas fluorescens AK32 showed effective results in terms of increase in root and shoot dry weight in maize (123, 130, 121, 120, 124g and 116, 126, 116, 114, 120g/pot, respectively) and wheat (130, 135, 125, 118, 140g and 105, 106, 110, 102, 110g/pot, respectively), in comparison to controls of maize and wheat crops. Thus, it might be concluded that PGPR strains AK21, AK31, AK14, AK19 and AK32 could be used as crop-enhancer and bio-fertilizer for production of maize and wheat

Isolation and identification of plant growth promoting rhizobacteria from maize (Zea mays L.) rhizosphere and their plant growth promoting effect on rice (Oryza sativa L.)

The use of plant growth promoting rhizobacteria is increasing in agriculture and gives an appealing manner to replace chemical fertilizers, pesticides, and dietary supplements. Th e objective of our research was to access the plant growth promotion traits of Pseudomonas aeruginosa, P. fl uorescens and Bacillus subtilis isolated from the maize (Zea mays L.) rhizosphere. In vitro studies showed that isolates have the potential to produce indole acetic acid (IAA), hydrogen cyanide, phosphate solubilisation, and siderophore. RNA analysis revealed that two isolates were 97% identical to P. aeruginosa strain DSM 50071 and P. aeruginosa strain NBRC 12689 (AK20 and AK31), while two others were 98% identical to P. fl uorescens strain ATCC 13525, P. fl uorescens strain IAM 12022 (AK18 and AK45) and one other was 99% identical to B. subtilis strain NCDO 1769 (AK38). Our gnotobiotic study showed signifi cant diff erences in plant growth variables under control and inoculated conditions. In the present research, it was observed that the isolated strains had good plant growth promoting eff ects on rice

Effect of salt stress-tolerant bacterial endophytes from Bougainvillea glabra on the growth of Triticum aestivum L. var. HD 2687 and Zea mays var. PSCL-4642

Wheat and corn crops contribute to the food security of humans by providing a nutrient-rich diet. However, their production in abiotic stress conditions such as salinity is limited. Endophytes exert a beneficial effect on plants through the decomposition of organic materials for smooth absorption, detoxification, and reduction of the effect of phytopathogenic microorganisms by increasing the immunity of host plants to resist phytopathogens and through nutrient deposition in plants responsible for reducing salt stress. The present study aimed to evaluate the NaCl tolerance efficiency of Triticum aestivum L. var. HD 2687 and Zea mays var. PSCL-4642 cultivars at the germination stage after inoculation with salt-tolerant bacterial endophyte BoGl21 isolated from Bougainvillea glabra. The seeds of both crops were tested for percentage of seed germination with/without bacteria at 50, 100, 150, and 200 mM NaCl concentrations. The BoGl21 isolate induced a significant increase in radicle length in corn (25.6 mm) as compared to that in wheat (10.3 mm) at 50 mM NaCl. However, at 100 mM NaCl, the radical length of wheat and corn seedlings was 5 mm and 8.8 mm, respectively. Inoculation of maize and wheat with the bacterial isolate significantly increased the plumule length of the germinated seeds as compared to that of controls. BoGl21 increased the plumule length of wheat as compared to that of the control seeds by 31.9, 11.7, and 4.8 mm at 50, 100, and 150 mM salinity stress, respectively. Inoculation of corn seeds with BoGl21 at the tested NaCl levels (50, 100, and 150 mM NaCl) increased the plumule length of the germinated seeds by 33.1, 22, 13.2, and 3.2 mm, respectively. The current research results support the hypothesis that bacterial endophytes could be beneficial to minimize the toxicity of saline stress on wheat and corn at the time of germination