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.