78 research outputs found
Engineering bacteria for bioremediation of persistent organochlorine pesticide lindane (γ-hexachlorocyclohexane)
No full textStrategies were designed for bioremediation of the highly persistent toxic pesticide γ-hexachlorocyclohexane (γ-HCH) or lindane from the environment. Lindane caused the loss of stress-protective chaperone GroEL, and inhibited photosynthesis, respiration and nitrogen-fixation in Anabaena, resulting in growth arrest. To alleviate lindane toxicity, the linA2 gene, encoding HCH dehydrochlorinase from Sphingomonas paucimobilis B90, was knocked-in at an innocuous locus in Anabaena genome and over-expressed from an eco-friendly light-inducible PpsbA1 promoter. The recombinant Anabaena degraded >98% of 10 ppm lindane within 6-10 days. A LinA2 overexpressing Escherichia coli strain could degrade 10 ppm of all the isomers of lindane within 1h and displayed a visual degradation zone on a newly designed histochemical plate containing 50mg lindane within 12h. The study demonstrates (a) bioremediation of traces of lindane prevalent in paddy fields, using bioengineered photoautotrophic Anabaena, and, (b) biodegradation of huge stockpiles of lindane, by employing recombinant live/dead E. coli
The Indian nitrogen challenge in a global perspective
No full textHuman activities have massively altered the global nitrogen (N) cycle, doubling annual production of reactive N (Nr) compounds from atmospheric dinitrogen (N2). The use of 120 Mt year−1 fertilizer N, with a global terrestrial/atmospheric N fixation of 285 Mt year−1, has provided huge benefits for global food production. However, nitrogen use efficiency (NUE) of the world food system is only ∼15%. The lost Nr creates a cascade of air and water pollution and greenhouse gas emissions, until it is eventually denitrified back to N2.
India clearly illustrates a dual N challenge for food and environment, consuming 17 Mt of N fertilizer annually (14% of the global total), which has increased since 1970 at 6% year−1 approximately. Emissions of nitrogen oxides (NOx) from combustion sources are also increasing rapidly at 6.5% year−1 currently. By comparison, population growth rate is lower (2% year−1), while ammonia (NH3) emission increase is even less (1%), pertaining to smaller changes in livestock numbers. At current rate, Indian NOx emissions will exceed NH3 emissions by 2055. India currently loses Nr worth US75 (38–151) billion year−1.
Only a small fraction of the Indian population consumes animal products, hence per capita Nr use and pollution is much less than in many developed countries. However, rates of meat consumption are increasing. While published projections from the UN Food and Agriculture Organization anticipate a doubling of South Asian fertilizer consumption from 2006 to 2050 (equivalent to 1.9% year−1 increase), these projections lack transparency and require reevaluation. In practice, the future nitrogen cycle for India will depend on scientific advances in agronomy, genetics and environment, and the extent to which government and society grasp the emerging opportunities for optimizing N management
Whether conversion of mangrove forest to rice cropland is environmentally and economically viable?
No full textEscherichia coli, but Not Staphylococcus aureus, Functions as a Chelating Agent That Exhibits Antifungal Activity against the Pathogenic Yeast Candida albicans
No full textHumans are colonized by diverse populations of microbes. Infections by Candida albicans, an opportunistic fungal pathogen, are a result of imbalances in the gut microbial ecosystem and are due to the suppressed immunity of the host. Here, we explored the potential effects of the polymicrobial interactions of C. albicans with Staphylococcus aureus, a Gram-positive bacterium, and Escherichia coli, a Gram-negative bacterium, in dual and triple in vitro culture systems on their respective growth, morphology, and biofilms. We found that S. aureus promoted the fungal growth and hyphal transition of C. albicans through cell-to-cell contacts; contrarily, both the cell and cell-free culture filtrate of E. coli inhibited fungal growth. A yet to be identified secretory metabolite of E. coli functionally mimicked EDTA and EGTA to exhibit antifungal activity. These findings suggested that E. coli, but not S. aureus, functions as a chelating agent and that E. coli plays a dominant role in regulating excessive growth and, potentially, the commensalism of C. albicans. Using animal models of systemic candidiasis, we found that the E. coli cell-free filtrate suppressed the virulence of C. albicans. In general, this study unraveled a significant antimicrobial activity and a potential role in the nutritional immunity of E. coli, and further determining the underlying processes behind the E. coli–C. albicans interaction could provide critical information in understanding the pathogenicity of C. albicans
Enhanced biodegradation of γ‐hexachlorocyclohexane (γ‐HCH) in HCH (commercial) acclimatized flooded soil: Factors affecting its development and persistence
No full text
Assessment of reactive nitrogen flows in Bangladesh’s agriculture sector
No full textTo assess the status of and trends in agricultural nitrogen (N) flows and their wider consequences for Bangladesh, in this study, we analyzed data from national and international bodies. The increased rates of N fertilizer applied for increased food production leaves behind a huge amount of unutilized reactive N (Nr). N fertilizer use is the largest in the crop sector, an important sector, where current annual consumption is 1190 Gg. The present combined annual Nr production from crop, fishery, and livestock sectors is ~600 Gg, while emissions of nitrous oxide (N2O), a potent greenhouse gas, are ~200 Gg. Poor N management results in Nr leaking into the environment, which has increased approximately 16-fold since 1961. One potential consequence is the disruption of ecosystem functioning. The balanced tradeoff between food production and reducing Nr input needs to be achieved. One solution to reducing Nr may be a holistic approach that optimizes N application rates and incorporates waste of one subsector as an input to another applying the principle of the circular economy
Managing reactive nitrogen in spring wheat cropping systems: insights from Kabul, Afghanistan
No full textAmmonia (NH₃) volatilization and nitrate leaching contribute to major losses of reactive nitrogen (Nr) in agriculture, leading to global environmental concerns. Effective measures are needed to mitigate Nr losses and improve nitrogen (N)-use efficiency in agricultural practices. This study, conducted in farmers' fields in Shewaki near Kabul City, Afghanistan, during the 2021 spring season, sought to address Nr-losses in agriculture. Nine treatments were organized into three categories: (A) animal manure + chemical fertilizer, (B) night soil + chemical fertilizer, and (C) chemical fertilizer alone, along with an unamended control. Chemical fertilizer and manure were applied at varying rates (±25% and a recommended rate) using both surface and sub-surface application methods. Sub-surface application reduced NH₃ emissions by 55% compared to surface application. Treatment group 'A' had a 32% NH₃ loss, while the unamended control (receiving N from irrigation water and dust only) showed a 13% loss. For nitrate leaching, group 'B' showed the highest loss, followed by group 'C'. Overall, agronomic practices reduced N-losses significantly, resulting in a net positive N-balance. Nuse efficiency was highest in group 'C' at 130%, followed by groups 'B' and 'A'. The findings suggest that sub-surface application techniques are effective in reducing N-losses and enhancing N-use efficiency, and highlight the potential to improve nutrient use efficiency by adjusting fertilizer and manure inputs in similar agricultural systems
- …
