North Eastern Hill University

About: North Eastern Hill University is a education organization based out in Shillong, Meghalaya, India. It is known for research contribution in the topics: Population & Ruthenium. The organization has 2318 authors who have published 4476 publications receiving 48894 citations.

Regulation of urease activity in the cyanobacterium Anabaena doliolum

Abstract: The effect of nitrogen sources on the activity of urease has been studied in the cyanobacterium Anabaena doliolum. De novo synthesis of urease occurred in the absence of an added nitrogen source, and the enzyme activity was almost equal when the medium contained either N2, NO3−, or urea. Ammonium grown cell showed repression in urease activity which was freed by l-methionine, dl-sulphoximine (MSX), an inhibitor of glutamine synthetase. NH4+, must therefore, be metabolised through glutamine synthetase before repressing the urease activity. NH4+ (up to 10 mM) did not inhibit the urease activity in vitro, suggesting that NH4+ does not inactivate the enzyme but represses its biosynthesis. When NH4+ grown cells were transferred to medium containing urea, the ability to hydrolyse urea required approximately 5 to 6 h for maximal expression. Chloramphenicol (50 μg ml−1) completely prevented the rise in urease activity. Ni2+ at concentrations of 0.01 and 0.05 μM enhanced the urease activity; however, the addition of 10mM citrate to the medium resulted in a drop in the increase in urease activity. The cells treated with chloramphenicol in combination with Ni2+ showed a higher level of urease activity as compared to chloramphenicol treated cells only, suggesting the antagonistic nature of Ni2+ against chloramphenicol mainly at the level of synthesis/activity of proteases.

Bioprospecting of Plant Growth Promoting Bacilli and Related Genera Prevalent in Soils of Pristine Sacred Groves: Biochemical and Molecular Approach

Abstract: Bacillus spp. and related genera native to soils of the pristine sacred groves from Meghalaya, India were characterized using biochemical and 16S rRNA gene analysis which revealed dominance of Bacillus, Paenibacillus, Lysinibacillus and Viridibacillus in the groves. Biochemical estimation was carried out for in vitro testing of plant growth promoting traits present in these isolates. PCR screening were performed for plant growth-promoting related genes involved in the biosynthesis of acid phosphatase (AcPho), indolepyruvate decarboxylase (ipdC), 1-aminocyclopropane-1-carboxylate deaminase (accd) and siderophore biosynthesis protein (asbA). 76% of the sacred grove isolates gave an amplified fragment for AcPho. Three of the isolates gave an amplified fragment for IpdC gene. Apart from 2 isolates, all the other isolates including the reference strains were positive for the amplification of the accd gene indicating their potential to produce ACC deaminase enzyme. 42% of the isolates gave an amplified fragment for asbA gene indicating the potential ability of these isolates to produce the catechol type siderophore, petrobactin. Overall findings indicated multiple PGP genetic traits present in these isolates which suggested that these isolates are capable of expressing multiple PGP traits. Phylogenetic and sequence analysis of accd and asbA genes from the isolates revealed that asbA genes from Paenibacillus taichungiensis SG3 and Paenibacillus tylopili SG24 indicated the occurrence of intergeneric horizontal transfer between Paenibacillus and Bacillus.

Development of a new vitrification solution, VSL, and its application to the cryopreservation of gentian axillary buds

Abstract: Vitrification methods are convenient for cryopreserving plant specimens, as the specimens are plunged directly into liquid nitrogen (LN) from ambient temperatures. However, tissues and species with poor survival are still not uncommon. The development of vitrification solutions with high survival that cover a range of materials is important. We attempted to develop new vitrification solutions using bromegrass cells and found that VSL, comprising 20% (w/v) glycerol, 30% (w/v) ethylene glycol, 5% (w/v) sucrose, 10% (w/v) DMSO and 10 mM CaCl2, gave the highest survival following cryopreservation, as determined by fluorescein diacetate staining. However, the cryopreserved cells showed little regrowth, for unknown reasons. To check its applicability, VSL was used to cryopreserve gentian axillary buds and the performance was compared with those of conventional vitrification solutions. Excised gentian stem segments with axillary buds (shoot apices) were two-step precultured with sucrose to induce osmotic tolerance prior to cryopreservation. Gentian axillary buds cryopreserved using VSL following the appropriate preculturing approach exhibited 78% survival (determined by the regrowth capacity), which was comparable to PVS2 and PVS1 and far better than PVS3. VSL had a wider optimal incubation time (20–45 min) than PVS2 and was more suitable for cryopreserving gentian buds. The optimal duration of the first step of the preculture was 7–11 days, and preculturing with sucrose and glucose gave a much higher survival than fructose and maltose. VSL was able to vitrify during cooling to LN temperatures, as glass transition and devitrification points were detected in the warming profiles from differential scanning calorimetry. VSL and its derivative, VSL+, seem to have the potential to be good alternatives to PVS2 for the cryopreservation of some materials, as exemplified by gentian buds.

Synthesis and characterization of some water soluble Zn(II) complexes with (E)-N-(pyridin-2-ylmethylene)arylamines that regulate tumour cell death by interacting with DNA.

Abstract: The synthesis and spectroscopic properties of nine water soluble zinc(II) complexes of (E)-N-(pyridin-2-ylmethylene)arylamines (Ln) with the general formula [Zn(X)2(Ln)] (X = Cl−, Br−, I−; (1–8)) and [Zn(μ-N3)(N3)(L3)]2 (9) are reported. The complexes were characterized by elemental analysis and their spectroscopic properties were studied using UV-Visible, fluorescence, IR and 1H NMR spectroscopies. The solid state structures of zinc(II) complexes 2–4 and 6–9 were established by single crystal X-ray crystallography. The majority of the structures are mononuclear with tetra-coordinate zinc centres (2–4, 6 and 7) except where L carries an additional donor atom capable of coordinating zinc (8), in which case the zinc atom has a distorted square pyramidal geometry. The centrosymmetric molecule of [Zn(μ-N3)(N3)(L3)]2 (9) is binuclear with the zinc atoms in a trigonal bipyramidal coordination environment. In general, the dichlorozinc derivatives 1, 3–5 and 8 exhibited moderately elevated in vitro cytotoxic potency towards the human epithelial cervical carcinoma (HeLa) cell line, with 4 as the best performer (IC50 value of 18 μM). Apoptosis-inducing activity, assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, showed that the zinc complexes interacted with DNA and thereby interfered the DNA binding of several transcription factors to its promoter sites, thus inhibiting gene transcription required for the biological activity of cells.