Significance Entry of bacteria into host cells critically depends on their proper engulfment by the plasma membrane. So far, actin polymerization has been described as a major driving force in this process. However, our study reveals that the interaction of the bacterial surface lectin LecA with the host cell glycosphingolipid Gb3 is fully sufficient to promote engulfment of Pseudomonas aeruginosa , whereas actin polymerization is dispensable. Hence, the formation of a “lipid zipper” represents a previously unidentified mechanism of bacterial uptake and demonstrates that bacterial pathogens have evolved lipid-based invasion strategies that may function in addition to protein receptor-based ones. Furthermore, by identifying the LecA/Gb3 interaction as the major invasion-promoting factor, our study provides new targets for drugs that may prevent bacterial invasion and dissemination.
Creation of affordable materials for constant release of silver ions in water is one of the most promising ways to provide microbially safe drinking water for all. Combining the capacity of diverse nanocomposites to scavenge toxic species such as arsenic, lead, and other contaminants along with the above capability can result in affordable, all-inclusive drinking water purifiers that can function without electricity. The critical problem in achieving this is the synthesis of stable materials that can release silver ions continuously in the presence of complex species usually present in drinking water that deposit and cause scaling on nanomaterial surfaces. Here we show that such constant release materials can be synthesized in a simple and effective fashion in water itself without the use of electrical power. The nanocomposite exhibits river sand-like properties, such as higher shear strength in loose and wet forms. These materials have been used to develop an affordable water purifier to deliver clean drinking water at US $2.5/y per family. The ability to prepare nanostructured compositions at near ambient temperature has wide relevance for adsorption-based water purification.hybrid | green | appropriate technology | frugal science | developing world S afe drinking water is a significant, but simple indicator of development. Its availability at point of use can save over 2 million human lives (1) (of the 3.575 million deaths caused by water, sanitation, and hygiene issues, 42.6% are due to diarrhea alone: 3.575 million × 0.426 = 1.523 million lives), can avoid over 2 billion diarrheal infections (2), and can contribute over $4 billion to the global gross domestic product (3) (formula used: Σ (number of deaths attributed to diarrhea in each country × corresponding country's per capita gross domestic product). Considering the challenges associated with traditional disinfectants (4), solutions based on state-of-the-art science and technology hold the key for safe drinking water (5) and novel approaches are being looked at (6, 7). It has been long known that silver, especially in nanoparticle form, is an effective disinfectant and works for a wide spectrum of bacteria and viruses (8, 9). Numerous approaches are available for the synthesis of biocidal silver nanoparticles or colloids, including the use of matrices (10-12). The biocidal property of silver nanoparticles, usually in the size range of 10-20 nm, is attributed to the release of trace quantities of silver ions in water (13-16), which, although being sufficient for microorganism killing, does not exhibit toxicity to humans (17,18). [Toxicity due to silver nanoparticles themselves is also known (16)]. Although a number of silver-based biocidal compositions have been synthesized, those have not been able to reach the masses in large volumes (e.g., silver nanoparticleloaded ceramic candles) (19). Massive deployment has been hampered due to the following reasons: (a) Drinking water contains many species (e.g., inorganic ions and organics) that anchor on the sur...
Silver is an indispensable metal but its use has to be minimised for sustainable growth. Much of the silver lost during use is unrecoverable; an example being its use as an antimicrobial agent, a property known since ages. While developing methods to create an affordable drinking water purifier especially for the developing world, we discovered that 50 parts per billion (ppb) of Ag+ released continuously from silver nanoparticles confined in nanoscale cages is enough to cause antimicrobial activity in conditions of normal water. Here we show that the antibacterial and antiviral activities of Ag+ can be enhanced ~1,000 fold, selectively, in presence of carbonate ions whose concentration was maintained below the drinking water norms. The protective layers of the organisms were affected during the carbonate-assisted antimicrobial activity. It is estimated that ~1,300 tons of silver can be saved annually using this new way to enhance its antimicrobial activity.
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