Browsing by Author "Sangeeta Paul"
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ThesisItem Open Access ALGINATE BIOPOLYMER PRODUCTION BY SELECTED BACTERIAL STRAINS(IARI, Division of Microbiology, 2012) ASHOKRAJ J; Sangeeta PaulBacteria are good source for production of various important biopolymers like alginate and poly β-hydroxybutyrate (PHB). In the present study twenty four different exopolysaccharide overproducing bacterial cultures were evaluated for their maximum potential for alginate and PHB production. Maximum yield of exopolysaccharides (3.9 g/l) and alginate (3.3 g/l) was obtained in Azotobacter chroococcum culture CBD13. While maximum yield of PHB (22.6 mg/l) was obtained in A. choococcum culture H15. Minimum yield of exopolysaccharides (1.3 g/l) and alginate (0.8 g/l) was obtained in bacterial culture L65. While no PHB production was observed in case of A. choococcum culture H11. In most of the cases with an increase in exopolysaccharide production, there was also an increase in alginate production.ThesisItem Open Access BIOCONTROL OF FUSARIUM UDUM BY CHITINOLYTIC BACTERIA IN PIGEON PEA(DIVISION OF MICROBIOLOGY ICAR- INDIAN AGRICULTURAL RESEARCH INSTITUTE, 2017) DUKARE AJINATH SHRIDHAR; Sangeeta PaulWilt disease caused by Fusarium udum Butler is one of the most important soil-borne diseases of pigeon pea (Cajanus cajan (L) Millsp.) throughout India and world. It is the most serious disease causing lethal damage to the crop and considerable economic losses. Presently, management of pathogens by excessive use of synthetic chemicals is effective and convenient but it has caused serious ecological, economic and social concerns. In recent times, biological control of F. udum using microorganisms that can grow and colonize in rhizosphere, has attracted attention throughout the world. In view of above consideration, the present study was conducted to study/investigate in vitro and in vivo biological control of F. udum by chitinolytic bacteria isolated from pigeon pea rhizosphere. 53 bacterial chitinolytic morphotypes were isolated from pigeon pea rhizospheric soil. In qualitative screening, thirteen isolates among the 53 evaluated, produced clear chitin hydrolysis zone (between 2.6 mm and 8.8 mm) on colloidal chitin agar (CCA) medium plates. Among these selected isolates, highest chitinase activity (798.35 U mg-1 protein) was detected in isolate NS-22, followed by isolate NS-1 (632.33 U mg-1 protein). In vitro antifungal assay against F. udum, eleven isolates were able to cause significant reduction in the mycelial growth of F. udum. Chitinolytic bacterial isolate NS-22 recorded highest fungal growth inhibition (67.57 %) followed by isolate NS-1 (62.16%). Five most promising chitinolytic isolates were further selected for studying in vivo antagonistic potential against F. udum under pot culture conditions and seed inoculation with chitinolytic bacteria (NS-1 and NS-22) resulted in better seed germination, reduced wilt incidence and improved plant biomass over all other treatments. Based on the in vitro and in vivo screening for antagonistic activity against F. udum, two most promising and effective chitinolytic bacterial isolates NS-1 and NS-22 were selected and characterized. Based on by 16s rRNA gene sequencing, bacterial isolate NS-1 was identified as Pseudomonas spp. while NS-22 was identified as Bacillus spp. The effect of different growth and cultural conditions on activity of extracellular chitinase enzyme of Pseudomonas spp. strain NS-1 and Bacillus spp. strain NS-22 was determined. Luria 148 broth as growth media, neutral pH range, temperature (30°C for Pseudomonas spp. strain NS-1 and 35°C for Bacillus spp. strain NS-22) was found optimum for induction of highest chitinase activity in these bacterial isolates. Among various carbon and metal ions, Luria broth supplemented with fructose and with Fe2+ ions supported maximum chitinase activity in both the selected bacteria (Pseudomonas spp. strain NS-1 and Bacillus spp. strain NS-22). Under in vitro studies, extracellular, diffusible and volatile metabolites produced by both these bacterial cultures exhibited antagonism against F. udum. Growth inhibition by means of reduction in mycelial dry weight of F. udum was also observed when both these bacteria were grown simultaneously/at different growth time of pathogen in PD broth. Hydrolytic enzymes (endochitinase, exochitinase, chitobiase, protease and lipase) related to biological disease suppression were also detected in both the selected cultures. Additionally, other biocontrol traits like production of siderophore, and ammonia were also detected in both antagonistic bacteria, while HCN was observed only in Pseudomonas spp. strain NS-1. Light and scanning microscopy study also revealed lysis, distortation, deformation and irregularity in hyphae morphology during interaction of the pathogen with the selected cultures. In vivo pot experimental study also supported the results obtained under in vitro study. Seed bacterization with the bacterial cultures of the pathogen challenged pigeon pea plants led to a higher induction of the different defense enzymes such as phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), peroxidase (PO), increase in total phenolics and chlorophyll content and reduced root mortality (%) over control. There was also increase in plant height, biomass and number of pods in treated plants. Application of selected cultures enhanced soil FDA, dehydrogenase activity and soil microbial biomass. It also reduced fusarium population in the soil. Thus, both these cultures, Pseudomonas spp. strain NS-1 and Bacillus spp. strain NS-22, exhibited good antagonistic potential against F. udum and can prove as promising candidates for biocontrol of fusarium wilt in pigeon pea.ThesisItem Open Access CHARACTERIZATION AND EVALUATION OF OSMOTOLERANT RHIZOBACTERIA FOR ALLEVIATION OF WATER DEFICIT STRESS IN MUSTARD(Division of Microbiology ICAR-Indian Agricultural Research Institute New Delhi, 2015) BANDEPPA; Sangeeta PaulDrought is the most common stress affecting plant growth and development and it is a major abiotic stress hindering agricultural productivity in majority of arid and semiarid regions of the world. Mustardis one of the most important oilseed crops grown in India. It is generally grown as rainfed crop, however, water deficit stress considerably impacts its growth and yield. Osmotolerant plant growth promoting bacteria can be harnessed for their beneficial properties under such conditionsso as to prevent deleterious effects of water stress on crop. In the present investigation, a total of 114 morphologically different bacteria were isolated from the rhizosphere of drought tolerant mustard cultivar DRMR 2352 using various media. Out of these 114 rhizobacterial isolates screened for osmotolerance, 14 isolates showed higher growth in presence of osmotic stress and were able to grow in nutrient broth supplemented with 40% PEG 6000. These 14 osmotolerant bacterial isolates were evaluated for their alleviation of water stress in drought susceptible mustard cultivar Pusa Karishma LES-39. Under in vitro conditions there was an increase in percent germination and seedling vigour of inoculated mustard seedling as compared to uninoculated control treatment exposed to water stress. A pot experiment conducted under water stress conditions revealed positive effect of inoculation with osmotolerant bacteria on shoot and root fresh weightand dry weight of mustard. Nearly all the plants inoculated with osmotolerant bacterial isolates were observed to have significantly higher water content in shoots and improved water use efficiency under water stress conditions. Two promising osmotolerant cultures NA D7 and MR D17 were selected for further studies. Effect of different concentrations of PEG 6000 on their PGPR activities were determined, like P solubilization, IAA production, GAproduction, ACC deaminase activity, exopolysaccharide production etc. The selected isolates improved seed germination and seedling vigour of mustard on exposure to different levels of water stress. The isolates were identified as Bacillus cereus and Bacillus sp. by 16S rDNA sequencing. 2 A pot culture experiment was carried out under drought and normal soil conditions to evaluate the effect of these cultures on mustard growth. Inoculation has a beneficial effect on plant biomass, productivity, oil content and root system architecture under both normal and water stress conditions.Various plant physiological parameters viz. amino acid, proline, starch, sugars, phenolics and chlorophyll, content were significantly enhanced in inoculated plants under water stress conditions. Inoculation with the osmotolerant bacteria significantly improved membrane stability index and relative water content; and decreased lipid peroxidation in plants under water stress conditions. Activity of antioxidative enzymes such as catalase, ascorbate peroxidase, glutathione reductase and superoxide dismutase were significantly enhanced in inoculated plants exposed to water stress conditions. Plant phosphorus and potassium contentswere considerably enhanced under water stress conditions due to inoculation with selected strains. However, response of the drought susceptible genotype to inoculation was markedly more than that observed for the tolerant genotype. Expression of drought responsive genes DREB 2 and DREB 1-2 was considerably enhanced due to inoculation under water stress conditions. Thus, osmotolerant bacteria possessing plant growth promoting activities can be used for drought stress alleviation in crops and to improve plant growth under water deficit stress.ThesisItem Open Access CHARACTERIZATION AND EVALUATION OF SALT TOLERANT BACTERIA FOR ALLEVIATION OF SALT STRESS IN MAIZE(IARI, DIVISION OF MICROBIOLOGY, 2011) BANDEPPA; Sangeeta PaulSalinization of soil is a serious problem and is increasing steadily in many parts of the world. Soil salinity affects the germination, establishment, growth and development of plants leading to huge losses in productivity. Maize, one of the major cereal crops in India, is a moderately salt sensitive plant. Yield reduction of more than 50% has been observed due to exposure of the plant to moderate salt stress. Beneficial microorganisms colonizing plant rhizosphere can influence plant growth and development. Salinity affects their survival, growth and plant growth promoting activities. Salt tolerant plant growth promoting bacteria can be harnessed for their beneficial properties in such environments in which other microorganisms hardly survive. In the present investigation, salt tolerant bacteria were characterized and evaluated for alleviation of salt stress in maize. Fifteen bacterial isolates were screened for salt tolerance. Based on their high salt tolerance, two cultures SSA61 and SSM66 were selected for further studies. Effect of different concentrations of NaCl on their growth was determined. Both the cultures were able to grow up to 15% NaCl concentration. The isolates were also characterized for their plant growth promoting activities like P solubilization, IAA production, ARA, siderophore and HCN production, ACC deaminase activity, etc. in the presence as well as absence of salt. Siderophore production was not observed in any of the isolates. With increase in NaCl concentration an increase in all the plant growth promoting activities was observed. However, 15% NaCl concentration had a slightly inhibitory effect on IAA production, ARA, siderophore and HCN production by the selected isolates. The isolates also improved seed germination of wheat in presence of salt. The isolates were identified as Bacillus sp. and Stenotrophomonas sp. by 16S rDNA sequencing. A pot culture experiment was carried out under saline soil and normal soil conditions to evaluate the effect of these cultures on maize growth. Various plant physiological parameters viz. amino acid, proline, starch, sugars, phenolics and chlorophyll, content, membrane stability index, membrane injury index, relative water content were also studied. Plant phosphorus, nitrogen, sodium and potassium contents were also determined. There was a decrease in membrane injury index while all other parameters studied were significantly enhanced due to inoculation with these cultures under salt stress. Thus, salt tolerant bacteria possessing plant growth promoting activities can be harnessed for salt stress alleviation in crops and to improve plant growth under salinity stress.ThesisItem Open Access CHARACTERIZATION AND EVALUATION OF SALT TOLERANT BACTERIA FOR ALLEVIATION OF SALT STRESS IN MAIZE(IARI, DIVISION OF MICROBIOLOGY, 2011) BANDEPPA; Sangeeta PaulSalinization of soil is a serious problem and is increasing steadily in many parts of the world. Soil salinity affects the germination, establishment, growth and development of plants leading to huge losses in productivity. Maize, one of the major cereal crops in India, is a moderately salt sensitive plant. Yield reduction of more than 50% has been observed due to exposure of the plant to moderate salt stress. Beneficial microorganisms colonizing plant rhizosphere can influence plant growth and development. Salinity affects their survival, growth and plant growth promoting activities. Salt tolerant plant growth promoting bacteria can be harnessed for their beneficial properties in such environments in which other microorganisms hardly survive. In the present investigation, salt tolerant bacteria were characterized and evaluated for alleviation of salt stress in maize. Fifteen bacterial isolates were screened for salt tolerance. Based on their high salt tolerance, two cultures SSA61 and SSM66 were selected for further studies. Effect of different concentrations of NaCl on their growth was determined. Both the cultures were able to grow up to 15% NaCl concentration. The isolates were also characterized for their plant growth promoting activities like P solubilization, IAA production, ARA, siderophore and HCN production, ACC deaminase activity, etc. in the presence as well as absence of salt. Siderophore production was not observed in any of the isolates. With increase in NaCl concentration an increase in all the plant growth promoting activities was observed. However, 15% NaCl concentration had a slightly inhibitory effect on IAA production, ARA, siderophore and HCN production by the selected isolates. The isolates also improved seed germination of wheat in presence of salt. The isolates were identified as Bacillus sp. and Stenotrophomonas sp. by 16S rDNA sequencing. A pot culture experiment was carried out under saline soil and normal soil conditions to evaluate the effect of these cultures on maize growth. Various plant physiological parameters viz. amino acid, proline, starch, sugars, phenolics and chlorophyll, content, membrane stability index, membrane injury index, relative water content were also studied. Plant phosphorus, nitrogen, sodium and potassium contents were also determined. There was a decrease in membrane injury index while all other parameters studied were significantly enhanced due to inoculation with these cultures under salt stress. Thus, salt tolerant bacteria possessing plant growth promoting activities can be harnessed for salt stress alleviation in crops and to improve plant growth under salinity stress.ThesisItem Open Access CHARACTERIZATION AND EVALUATION OF SALT TOLERANT BACTERIA FOR ALLEVIATION OF SALT STRESS IN MAIZE(IARI, DIVISION OF MICROBIOLOGY, 2011) BANDEPPA; Sangeeta PaulSalinization of soil is a serious problem and is increasing steadily in many parts of the world. Soil salinity affects the germination, establishment, growth and development of plants leading to huge losses in productivity. Maize, one of the major cereal crops in India, is a moderately salt sensitive plant. Yield reduction of more than 50% has been observed due to exposure of the plant to moderate salt stress. Beneficial microorganisms colonizing plant rhizosphere can influence plant growth and development. Salinity affects their survival, growth and plant growth promoting activities. Salt tolerant plant growth promoting bacteria can be harnessed for their beneficial properties in such environments in which other microorganisms hardly survive. In the present investigation, salt tolerant bacteria were characterized and evaluated for alleviation of salt stress in maize. Fifteen bacterial isolates were screened for salt tolerance. Based on their high salt tolerance, two cultures SSA61 and SSM66 were selected for further studies. Effect of different concentrations of NaCl on their growth was determined. Both the cultures were able to grow up to 15% NaCl concentration. The isolates were also characterized for their plant growth promoting activities like P solubilization, IAA production, ARA, siderophore and HCN production, ACC deaminase activity, etc. in the presence as well as absence of salt. Siderophore production was not observed in any of the isolates. With increase in NaCl concentration an increase in all the plant growth promoting activities was observed. However, 15% NaCl concentration had a slightly inhibitory effect on IAA production, ARA, siderophore and HCN production by the selected isolates. The isolates also improved seed germination of wheat in presence of salt. The isolates were identified as Bacillus sp. and Stenotrophomonas sp. by 16S rDNA sequencing. A pot culture experiment was carried out under saline soil and normal soil conditions to evaluate the effect of these cultures on maize growth. Various plant physiological parameters viz. amino acid, proline, starch, sugars, phenolics and chlorophyll, content, membrane stability index, membrane injury index, relative water content were also studied. Plant phosphorus, nitrogen, sodium and potassium contents were also determined. There was a decrease in membrane injury index while all other parameters studied were significantly enhanced due to inoculation with these cultures under salt stress. Thus, salt tolerant bacteria possessing plant growth promoting activities can be harnessed for salt stress alleviation in crops and to improve plant growth under salinity stress.ThesisItem Open Access DIVERSITY OF OSMOTOLERANT ENDOPHYTIC BACTERIA IN PEARL MILLET(DIVISION OF MICROBIOLOGY INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI, 2014) MANJUNATHA B S; Sangeeta PaulPlant growth in agricultural soils is influenced by many abiotic and biotic factors. Water stress is a major factor severely affecting crop productivity. Beneficial microorganisms colonizing plants’ interiors can influence plant growth and development. Osmotic stress affects their survival, growth and plant growth promoting activities. Osmotolerant plant growth promoting bacteria can be harnessed for their beneficial properties in such environments in which other microorganisms hardly survive. In the present investigation, endophytic bacteria were isolated from the drought resistant and susceptible cultivars of pearl millet using various media selective for specific groups of bacteria. Bacteria belonging to diverse groups such as gram negative bacteria, gram positive bacteria, oligotrophs, diazotrophs were found harbouring interiors of pearl millet plant. Higher populations of gram positives and oligotrophs were obtained in all the tissues and diazotrophic populations in leaves of both the cultivars of pearl millet. No fluorescent pseudomonads were observed. A total of 215 morphologically different endophytic bacteria were isolated from different tissues of the two cultivars such as roots, stem and leaves. Out of 215 bacterial isolates screened, 50 isolates were found showing high osmotic stress tolerance. Most of the isolates showed reduction in their growth under osmotic stress. Four isolates viz. KPRR22, RPRS14, KPRL10 and MPSL2 showed higher growth in presence of osmotic stress as compared to control conditions. Effect of osmotic stress on growth of the comparatively osmotolerant bacteria was determined. Out of the 50 cultures screened, only 13 and 3 were able to grow in medium with 40% and 50% PEG 6000, respectively. These osmotolerant endophytic bacteria were characterized for their plant growth promoting activities viz. P-solubilization, IAA production, nitrogen fixation, siderophore and HCN production and ACC deaminase activity. These isolates were observed to possess multiple plant growth promoting activities. A very high incidence of IAA production and siderophore production ability was observed. Nearly forty percent of the isolates also possessed P-solubilization and ACC deaminase activity. Only three cultures possessed nitrogen fixing ability. Osmotic stress had a beneficial effect on P-solubilization and HCN production abilities of most of the isolates. However, osmotic stress had an inhibitory effect on IAA production, nitrogen fixation and siderophore production abilities of most of the cultures. All these isolates were analyzed for genetic diversity based on RFLP analysis of 16S rRNA. These osmotolerant isolates were placed in 16 phylogenetic clusters, at 93% similarity, after RFLP analysis of their 16S rRNA. Sequencing of 16S rRNA of 16 representative isolates followed by BLAST search revealed that the majority of the isolates belonged to Firmicutes and only a few belonged to Proteobacteria. Species of Bacillus were the dominant osmotolerant endophytic bacteria colonizing interiors of pearl millet.ThesisItem Open Access Elucidating the effect of plant-bacterial interactions on seed germination and root colonization in mustard (Brassica juncea L.) under water deficit stress condition(DIVISION OF MICROBIOLOGY ICAR- INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI, 2020) NIVETHA N; Sangeeta PaulDrought is considered as major abiotic stress affecting seed germination, plant growth and crop productivity. Mustard an important oilseed crop is prone to be affected by drought. Rhizobacteria inoculation help crops to withstand stress. Plant root colonisation, an important factor for maximizing benefits from inoculation, is impacted by osmotic stress. So, deciding the optimum rhizobacterial density, mechanisms behind germination enhancement and colonization under osmotic stress is required for optimizing benefits from inoculation. In the present study, influence of different inoculum densities of Bacillus sp. strain MRD-17 and B. casamancensis strain MKS-6 on seed germination in vitro and growth of mustard in pot experiment, under water deficit stress were investigated. Rhizobacterial population densities ranging from 105 to 107 cfu/mL, were found to be stimulatory on seedling fresh weight in vitro; and on shoot and root fresh weight at 30 days after sowing in pot experiment under control and water deficit stress condition. However, higher inoculum densities (1011 cfu/mL) of both rhizobacteria had an inhibitory effect on seedling vigour and plant growth. Under sterile condition, there was beneficial effect of stimulatory and adverse effect of inhibitory population on plant growth while under unsterile conditions, adverse effects of inhibitory population was observed only on root fresh weight. Under sterile condition, rhizoplane population of inoculated bacteria more than 109 cfu/g was inhibitory and 106 to 108 cfu/g was beneficial for plant growth. Lower population densities of the inoculated rhizobacteria were observed on rhizoplane, under unsterile condition. Thus, population densities of rhizobacteria on roots had major impacts on seedling vigour and plant growth. Under no stress condition, germination of seedlings was not affected by IP inoculation, but post-germinative growth was affected. Inhibitory effect of IP and stimulatory effect of BP populations were observed on seedling fresh weight and length. Under osmotic stress condition, inoculation enhanced seedling germination, fresh weight and length. Rhizobacterial inoculation increased activities of enzymes involved in reserve hydrolysis in seedlings and highest was observed in IP under no stress condition and BP under osmotic stress condition. Higher gibberellic acid content was noted in inoculated plants under both conditions; while abscisic acid content was higher in inoculated seedlings onlyunder no stress condition. Inoculation with IP and BP reduced osmolyte accumulation in plants under osmotic stress condition. Expression of genes involved in the biosynthesis of reserve hydrolytic enzymes BjICL and BjMLS were significantly upregulated in IB and BP inoculated seedlings under no stress and osmotic stress conditions, respectively. BjABCD1 was upregulated under no stress and downregulated under osmotic stress upon rhizobacteria inoculation. Under no stress condition, inoculated seedlings showed higher expression of BjGA20Ox. There was upregulation of BjNCED3, BjABI5 and BjRGL2 genes involved in ABA biosynthesis, ABA and GA mediated repression of growth, respectively in IP inoculated seedlings. Under osmotic stress condition in inoculated seedlings, down-regulation of genes BjP5CS, BjBADH2 involved in osmolyte accumulation and BjDREB1-2, BjDREB2 involved in the regulation of ABA independent signalling pathway, indicated decrease in stress. Analysis of root exudates indicated that osmotic stress had significant impact on sugars, organic acids, fatty acids, phenolics and flavonoid composition. Osmotic stress also had a positive influence on swimming and twitching motility and chemotactic response B. casamancensis strain MKS-6. Osmotic stress had beneficial effect on biofilm production ability of rhizobacteria. Osmotic stress significantly enhanced cell wall hydrolytic enzymes production by Bacillus sp. strain MRD-17, in vitro and in vivo. There was induction of defence enzymes upon rhizobacterial inoculation. Osmotic stress and root exudates induced changes in the cell surface components of rhizobacteria and only root exudates influenced expression profile of rhizobacterial cell wall proteins. Rhizobacteria Bacillus sp. strain MRD-17 and B. casamancensis strain MKS-6 improved seed germination under osmotic stress condition with great colonization ability. The beneficial effect of these strains can be harnessed for drought stress alleviation in mustard by developing these into bio-formulations.ThesisItem Open Access STUDIES ON BIODEGRADATION OF SELECTED AZO DYE(IARI, DIVISION OF MICROBIOLOGY, 2010) JYOTI KUMAR THAKUR; Sangeeta PaulSynthetic dyes and pigments are widely used nowadays in textile, paper printing, food, cosmetics and pharmaceutical industries. These dyes are released into the environment from two major sources, the textile and the dye manufacturing industries. Contamination of surface water with dyes from these textile and dye manufacturing industries represents a serious ecological problem. World wide 7×105 metric tonnes of the dyes and pigments are produced out of which azo dye represents 70%. Azo dyes are the largest group of man made chemicals since aromatic azo and sulfo groups are not synthesized in nature and hence azo dyes are considered to be xenobiotics. In the present investigation, biodegradation of sulfonated diazo dye Red HE7B by Bacillus sp. Azo1, isolated from textile dyeing mill effluent contaminated soil, was studied. Numerical prevalence of the dye decolourizer present in contaminated sample soil collected from various sites was estimated by most probable number technique. Highest number of dye decolourizer was found in the soil sample collected from textile mill effluent contaminated field soil left barren followed by rice field adjacent to main drainage carrying effluent. Out of the six isolates, Azo1 and Azo5 showed remarkably good decolourization ability during initial screening, but further study showed that decolourization potential of Azo5 was quite variable and hence rest of the experiments were conducted with Azo1. This isolate decolourized 100% of the dye at 50mg/l and 71% at 200mg/l dye concentrations at 300C. Decolourization of dye was recorded from pH 5 to 9 with maximum declourization observed at pH 7. Among various carbon sources tested, citric acid proved to be the best followed by starch. Least decolourization was observed when glucose was used as a carbon source. Effect of aeration on decolourization of Red HE7B was negative and best decolourization was observed under static condition. Biodegradation of the dye was confirmed by TLC and HPLC. High levels of induction in activities of key enzymes like azoreductase and laccase was suggestive of involvement of these enzymes in biodegradation of Red HE7B. Mass spectra of degradation product obtained by GCMS showed formation of a number of products, some of which were identified and a tentative pathway of degradation was worked out. Phytotoxicity study of Red HE7B and its degradation product showed reduction in root length, shoot length and fresh weight of seedling with more effect on root length of wheat, radish and mustard in presence of dye. Biodegradation product of the dye did not cause any significant effect on these parameters indicating it as to be nonphytotoxic. Hence biodegradation of the dye Red HE7B by Bacillus sp. Azo1 can be economic and ecofriendly option for textile mill caused pollution.ThesisItem Open Access Understanding interactions between osmotolerant rhizobacteria and mustard under water deficit stress conditions(DIVISION OF MICROBIOLOGY ICAR- INDIAN AGRICULTURAL RESEARCHINSTITUTE NEW DELHI, 2020) ARAMBAM ASHA DEVI; Sangeeta PaulDrought stress is considered to be one of the most predominant abiotic stresses, causing a setback in crop production worldwide. Mustard is one among the major oil seed crops of India that is grown in rainfed lands. Recent studies indicate that employing osmotolerant rhizobacteria can help plants cope with drought stress which is an ecofriendly and cost-effective method. In the present investigation, eleven osmotolerant rhizobacterial cultures isolated from mustard and nagphani plants were evaluated for their effect on growth and yield of drought sensitive Brassica juncea variety Pusa Karishma LES-39 under water deficit stress condition. Plants inoculated with Bacillus cereus strain NAD-7 and Bacillus casamancensis strain MKS-6 exhibited superior performance in yield and growth, thus were selected for further studies. The effect of osmotic stress on mustard-rhizobacterial interactions was studied in detail. It was observed that osmotic stress significantly affected the rhizobacteriamustard root interaction. Also the quality and quantity of sugar monomers of both the rhizobacterial EPS was improved. The protein and phenolics profile of NAD-7 and MKS-6 were altered in the presence of osmotic stress. It was also found that several proteins of mustard roots were differentially expressed due to osmotic stress and inoculation treatment. Further, a pot experiment was conducted to determine the effect of inoculation with osmotolerant rhizobacterial strains NAD-7 and MKS-6 during vegetative and reproductive growth stages under drought stress conditions. It was observed that under drought stress, the inoculated plants exhibited better root and shoot biomass over uninoculated treatment during both stages. These observations led to investigation into the physiological, biochemical and molecular mechanisms involved. The inoculated plants outperformed in various parameters namely RWC, MSI and photosynthetic pigments in comparison to uninoculated conditions. The net photosynthetic rate, stomatal conductance and sugar contents were better in case of inoculated plants under drought stress. The proline content was significantly reduced by inoculation under drought stress during both stages and was interpreted as the improvement in plant health status by microbes. The H2O2 content of inoculated plants was lowered significantly and the activity of SOD, CAT and APX was significantly high in inoculated plants. Finally the hormonal regulation of plant growth was studied under drought during both stages. HPLC analysis of root samples showed that the level of auxin (IAA) was significantly higher in inoculated plants under stress that must have influenced the root growth during both stages. In leaves, the similar trend was followed for hormones namely GA and ABA. This also was explanatory to improved shoot growth and flowering. The expression of genes involved in the hormone biosynthetic pathways BjYUCCA1, BjNCED3 and BjGA20ox correlated with the hormone levels. Similarly, the transcript level of BjFeSOD and BjP5CSB, various stress signaling pathway genes namely BjDREB1-2, BjDREB2 and BjNAC14 were upregulated in inoculated plants under drought stress during both stages. The data on biomass, yield and oil content upon inoculation showed relatively superior performance even under drought stress conditions. It also appeared that the vegetative stage was more responsive to rhizobacterial inoculation than reproductive stage under drought. These investigations indicate the potency of rhizobacteria in reducing the negative impacts of drought stress in mustard. It can serve as potent biofertilizer to sustain crop production under stressed environment. Keywords :- Bacillus cereus, Rhizobacterial, Biosynthetic