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Assam Agricultural University, Jorhat

Assam Agricultural University is the first institution of its kind in the whole of North-Eastern Region of India. The main goal of this institution is to produce globally competitive human resources in farm sectorand to carry out research in both conventional and frontier areas for production optimization as well as to disseminate the generated technologies as public good for benefitting the food growers/produces and traders involved in the sector while emphasizing on sustainability, equity and overall food security at household level. Genesis of AAU - The embryo of the agricultural research in the state of Assam was formed as early as 1897 with the establishment of the Upper Shillong Experimental Farm (now in Meghalaya) just after about a decade of creation of the agricultural department in 1882. However, the seeds of agricultural research in today’s Assam were sown in the dawn of the twentieth century with the establishment of two Rice Experimental Stations, one at Karimganj in Barak valley in 1913 and the other at Titabor in Brahmaputra valley in 1923. Subsequent to these research stations, a number of research stations were established to conduct research on important crops, more specifically, jute, pulses, oilseeds etc. The Assam Agricultural University was established on April 1, 1969 under The Assam Agricultural University Act, 1968’ with the mandate of imparting farm education, conduct research in agriculture and allied sciences and to effectively disseminate technologies so generated. Before establishment of the University, there were altogether 17 research schemes/projects in the state under the Department of Agriculture. By July 1973, all the research projects and 10 experimental farms were transferred by the Government of Assam to the AAU which already inherited the College of Agriculture and its farm at Barbheta, Jorhat and College of Veterinary Sciences at Khanapara, Guwahati. Subsequently, College of Community Science at Jorhat (1969), College of Fisheries at Raha (1988), Biswanath College of Agriculture at Biswanath Chariali (1988) and Lakhimpur College of Veterinary Science at Joyhing, North Lakhimpur (1988) were established. Presently, the University has three more colleges under its jurisdiction, viz., Sarat Chandra Singha College of Agriculture, Chapar, College of Horticulture, Nalbari & College of Sericulture, Titabar. Similarly, few more regional research stations at Shillongani, Diphu, Gossaigaon, Lakhimpur; and commodity research stations at Kahikuchi, Buralikson, Tinsukia, Kharua, Burnihat and Mandira were added to generate location and crop specific agricultural production packages.

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20202
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Subject: Agricultural Biotechnology × Author: Chowdhury, Naimisha × End date: 2023 × Start date: 2020 ×
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    ThesisItemOpen Access
    Study on Acid Stress Response in Bacillus amyloliquefaciens
    (AAU, Jorhat, 2020-01) Chowdhury, Naimisha; Barooah, Madhumita
    Soil bacteria have evolved various mechanisms to adapt to stress environmental conditions such as temperature, salinity, drought and low pH condition of soil. Among the several environmental stress conditions, soil acidity an important factor influencing physicochemical and biological properties of soil along with microbial diversity and crop production is an emerging issue of immense concern due to its wide spread distribution across the globe. Although low soil pH restricts the number and diversity of bacteria, it is known that some soil bacteria are able to thrive in such conditions having evolved various mechanisms. The isolate Bacillus amyloliquefaciens MBNC can survive in low pH condition (upto pH 4.0). Moreover it can retain its antagonistic and plant growth promotion attributes under acidic condition. Early log phase cells of B.amyloliquefaciens MBNC were more susceptible to extreme pH than the late log phase cells. In addition, pre-exposed B.amyloliquefaciens MBNC cells to moderate acid condition had higher survival rate in extreme acid. In-vitro production of indole-3-acetic acid and gibberellic acid by B.amyloliquefaciens MBNC at neutral condition was higher (12.82±0.12 μg/ml and 35.15±0.005 μg/ml respectively) than at acidic condition (07.27±0.06 μg/ml and 26.66±0.003 μg/ml). Maximum antagonistic effect against fungal pathogens were shown 3 days post inoculation under acidic condition. High Resolution Mass Spectroscopy results shows the presence of surfactin C13 (exact mol.mass 1007.651836 g/mol) and surfactin C14 (exact mol.mass 1021.6677486 g/mol) in chloroform-methanol extract of both pH 7.0 and pH 4.5. Surfactin (exact mol.mass 1035.683136 g/mol) and iturinD was detected only in the extract of pH 4.5 and pH 7.0 respectively. For differential expression analysis a total of 22 genes were selected. Genes relating to maintenance of cell integrity (membrane integrity) showed increase expression under acid stress with an exception of spoA, flotilin and pdaA. Acid stress induce the environmental and energy stress regulon SigB, general stress protein gspA and the major molecular chaperones DnaK and GroES. pH-responsive gene, atpB (coding for the beta sub-unit of the F1F0-ATPase enzyme),cytochrome bd oxidase (cydA) and gene for nitrate reductase was upregulated. Cadmium, cobalt, and zinc/H/K antiporter (czcD), Iron-uptake system responsive genes (feuABC) and osmotic stress related gene pyrroline-5-carboxylate reductase (proC) was upregulated. Acidic pH upregulated acetoin production (alsDS), a pathway known to shunt fermentation into neutral products, minimizing acid production. Acid also upregulated a large number of NAD(P)-dependent dehydrogenases: alcohol dehydrogenase (eutG), formate dehydrogenases (fdhA), malate dehydrogenase (mdh). These enzymes are capable of removing acidity through NAD(P)H which transfers electrons to the electron transport system (ETS) and pumps protons out of the cell. The cupin gene (cupin superfamily of proteins) involved in the modification of cell wall carbohydrates showed manifold upregulation under acid stress. To further validate this, targeted mutagenesis of cupin in B.amyloliquefaciens MBNC was performed using pMUTIN4 integration vector. The transformation efficiency was very low with 32 transformants/μg pmutcupin DNA. The integration of pmutcupin into the chromosome of B.amyloliquefaciens MBNC was confirmed by PCR amplification of ermAM and bla gene using the genomic DNA of the transformed B.amyloliquefaciens MBNC. The mutant isolate, Δcupin failed to grow in nutrient broth at pH 4.5 which confirms the role of cupin gene in acid stress. Inability to form biofilm and scanning electron microscopy (SEM) of B.amyloliquefaciens MBNC wild type and its cupin mutant (Δcupin) at neutral pH confirms the targeted mutagenesis of cupin gene.
  • Thumbnail Image
    ThesisItemOpen Access
    Study on Acid Stress Response in Bacillus amyloliquefaciens
    (AAU, Jorhat, 2020-01) Chowdhury, Naimisha; Barooah, Madhumita
    Soil bacteria have evolved various mechanisms to adapt to stress environmental conditions such as temperature, salinity, drought and low pH condition of soil. Among the several environmental stress conditions, soil acidity an important factor influencing physicochemical and biological properties of soil along with microbial diversity and crop production is an emerging issue of immense concern due to its wide spread distribution across the globe. Although low soil pH restricts the number and diversity of bacteria, it is known that some soil bacteria are able to thrive in such conditions having evolved various mechanisms. The isolate Bacillus amyloliquefaciens MBNC can survive in low pH condition (upto pH 4.0). Moreover it can retain its antagonistic and plant growth promotion attributes under acidic condition. Early log phase cells of B.amyloliquefaciens MBNC were more susceptible to extreme pH than the late log phase cells. In addition, pre-exposed B.amyloliquefaciens MBNC cells to moderate acid condition had higher survival rate in extreme acid. In-vitro production of indole-3-acetic acid and gibberellic acid by B.amyloliquefaciens MBNC at neutral condition was higher (12.82±0.12 μg/ml and 35.15±0.005 μg/ml respectively) than at acidic condition (07.27±0.06 μg/ml and 26.66±0.003 μg/ml). Maximum antagonistic effect against fungal pathogens were shown 3 days post inoculation under acidic condition. High Resolution Mass Spectroscopy results shows the presence of surfactin C13 (exact mol.mass 1007.651836 g/mol) and surfactin C14 (exact mol.mass 1021.6677486 g/mol) in chloroform-methanol extract of both pH 7.0 and pH 4.5. Surfactin (exact mol.mass 1035.683136 g/mol) and iturinD was detected only in the extract of pH 4.5 and pH 7.0 respectively. For differential expression analysis a total of 22 genes were selected. Genes relating to maintenance of cell integrity (membrane integrity) showed increase expression under acid stress with an exception of spoA, flotilin and pdaA. Acid stress induce the environmental and energy stress regulon SigB, general stress protein gspA and the major molecular chaperones DnaK and GroES. pH-responsive gene, atpB (coding for the beta sub-unit of the F1F0-ATPase enzyme),cytochrome bd oxidase (cydA) and gene for nitrate reductase was upregulated. Cadmium, cobalt, and zinc/H/K antiporter (czcD), Iron-uptake system responsive genes (feuABC) and osmotic stress related gene pyrroline-5-carboxylate reductase (proC) was upregulated. Acidic pH upregulated acetoin production (alsDS), a pathway known to shunt fermentation into neutral products, minimizing acid production. Acid also upregulated a large number of NAD(P)-dependent dehydrogenases: alcohol dehydrogenase (eutG), formate dehydrogenases (fdhA), malate dehydrogenase (mdh). These enzymes are capable of removing acidity through NAD(P)H which transfers electrons to the electron transport system (ETS) and pumps protons out of the cell. The cupin gene (cupin superfamily of proteins) involved in the modification of cell wall carbohydrates showed manifold upregulation under acid stress. To further validate this, targeted mutagenesis of cupin in B.amyloliquefaciens MBNC was performed using pMUTIN4 integration vector. The transformation efficiency was very low with 32 transformants/μg pmutcupin DNA. The integration of pmutcupin into the chromosome of B.amyloliquefaciens MBNC was confirmed by PCR amplification of ermAM and bla gene using the genomic DNA of the transformed B.amyloliquefaciens MBNC. The mutant isolate, Δcupin failed to grow in nutrient broth at pH 4.5 which confirms the role of cupin gene in acid stress. Inability to form biofilm and scanning electron microscopy (SEM) of B.amyloliquefaciens MBNC wild type and its cupin mutant (Δcupin) at neutral pH confirms the targeted mutagenesis of cupin gene.