Growth inhibition by alpha-aminoadipate and reversal of the effect by specific amino acid supplements in Saccharomyces cerevisiae

The growth of Saccharomyces cerevisiae wild-type strain X2180 in minimal medium was inhibited by the addition of higher-than-supplementary levels of alpha-aminoadipate. This inhibitory effect was reversed by the addition of arginine, asparagine, aspartate, glutamine, homoserine, methionine, or serine as single amino acid supplements. Mutants belonging to the lys2 and lys14 loci were able to grow in lysine-supplemented alpha-aminoadipate medium, although not as well as when selected amino acids were added. Growth in alpha-aminoadipate medium by all strains was accompanied by an accumulation of alpha-ketoadipate. Glutamate:keto-adipate transaminase levels were derepressed two- to fivefold in lys2 mutants using alpha-aminoadipate as a nitrogen source. Wild-type strain X2180 growing in amino acid-supplemented AA medium exhibited higher levels of alpha-aminoadipate reductase. Mutants unable to use alpha-aminoadipate without amino acid supplementation were obtained by treatment of lys2 strain MW5-64 and were shown to have glutamate: ketoadipate transaminase activity and to lack alpha-aminoadipate reductase activity. Altered cell morphologies, including increased size, multiple buds, pseudohyphae, and germ tubes, evidenced by cells grown in alpha-aminoadipate medium suggest that higher-than-supplementary levels of alpha-aminoadipate result in an impairment of cell division.     

Enzymic cleavage of the α-linkages in agarose,to yield agaro-oligosaccharides

An α-agarase was isolated from a Gram-negative marine bacterium that liquefies agar. The enzyme was purified by chromatography on diethylaminoethyl-cellulose (HO^? form) buffered at pH 7.2. The purified enzyme specifically cleaves (1 →3)-α-L-linkages in agarose, yielding a homologous series of agaro-oligosaccharides. Agarotetraitol and agarohexaitol were characterized.     

Dental pulp–derived stem cells inhibit osteoclast differentiation by secreting osteoprotegerin and deactivating AKT signalling in myeloid cells

Osteoclasts (OCs) differentiate from the monocyte/macrophage lineage, critically regulate bone resorption and remodelling in both homeostasis and pathology. Various immune and non-immune cells help initiating activation of myeloid cells for differentiation, whereas hyper-activation leads to pathogenesis, and mechanisms are yet to be completely understood. Herein, we show the efficacy of dental pulp–derived stem cells (DPSCs) in limiting RAW 264.7 cell differentiation and underlying molecular mechanism, which has the potential for future therapeutic application in bone-related disorders. We found that DPSCs inhibit induced OC differentiation of RAW 264.7 cells when co-cultured in a contact-free system. DPSCs reduced expression of key OC markers, such as NFATc1, cathepsin K, TRAP, RANK and MMP-9 assessed by quantitative RT-PCR, Western blotting and immunofluorescence detection methods. Furthermore, quantitative RT-PCR analysis revealed that DPSCs mediated M2 polarization of RAW 264.7 cells. To define molecular mechanisms, we found that osteoprotegerin (OPG), an OC inhibitory factor, was up-regulated in RAW 264.7 cells in the presence of DPSCs. Moreover, DPSCs also constitutively secrete OPG that contributed in limiting OC differentiation. Finally, the addition of recombinant OPG inhibited OC differentiation in a dose-dependent manner by reducing the expression of OC differentiation markers, NFATc1, cathepsin K, TRAP, RANK and MMP9 in RAW 264.7 cells. RNAKL and M-CSF phosphorylate AKT and activate PI3K-AKT signalling pathway during osteoclast differentiation. We further confirmed that OPG-mediated inhibition of the downstream activation of PI3K-AKT signalling pathway was similar to the DPSC co-culture–mediated inhibition of OC differentiation. This study provides novel evidence of DPSC-mediated inhibition of osteoclastogenesis mechanisms.     

Management of abiotic stresses by microbiome-based engineering of the rhizosphere

Abiotic stresses detrimentally affect both plant and soil health, threatening food security in an ever-increasing world population. Sustainable agriculture is necessary to augment crop yield with simultaneous management of stresses. Limitations of conventional bioinoculants have shifted the focus to more effective alternatives. With the realization of the potential of rhizospheric microbiome engineering in enhancing plant's fitness under stress, efforts have accelerated in this direction. Though still in its infancy, microbiome-based engineering has gained popularity because of its advantages over the microbe-based approach. This review briefly presents major abiotic stresses afflicting arable land, followed by an introduction to the conventional approach of microbe-based enhancement of plant attributes and stress mitigation with its inherent limitations. It then focuses on the significance of the rhizospheric microbiome and possibilities of harnessing its potential by its strategic engineering for stress management. Further, success stories related to two major approaches of microbiome engineering (generation of synthetic microbial community/consortium, and host-mediated artificial selection) pertaining to stress management have been critically presented. Together with bringing forth the challenges associated with the wide application of rhizospheric microbiome engineering in agriculture, the review proposes the adoption of a combinational scheme for the same, bringing together ecological and reductionist approaches for improvised sustainable agricultural practices.     

Evaluation of coliforms as indicators of water quality in India

P.W. RAMTEKE, J.W. BHATTACHARJEE, S.P. PATHAK AND N. KALRA. 1992. The total and thermotolerant coliform counts in rural drinking water derived from ground water, piped supplies and surface water are reported for a number of areas in India. To evaluate these counts as indicators of recent faecal contamination the total coliforms and thermotolerant coliforms isolated have been identified. Thermotolerant Escherichia coli formed 11.7% of the total coliforms and 75.1% of the thermotolerant coliforms. Citrobacter sp. (20.4%) and Klebsiella sp. (50.9%) were the other common total coliforms isolated and, among the thermotolerant coliforms, Klebsiella sp. (16.4%) was the only other organism frequently encountered. The total coliform counts were significantly correlated with water temperature. The applicability in tropical areas of standards developed for temperate climates is discussed.