To date, much of the work that has been done in the field of bioremediation has focused on the use of soil dwelling bacteria or complex fungi. Little attention has been given to the remediating capabilities of organisms like cyanobacteria because many of the mechanisms they employ to produce energy are less efficient or take longer than those used by other kinds of bacteria because most of their energy comes from the sun. This is not necessarily accurate, though, and in some cases photosynthetic cyanobacteria are more suitable candidates for bioremediation because they need only to be exposed to sunlight to break down certain compounds effectively, and no further nutrient amendment is necessary. Those species that live in close association with a contamination source usually find a way to reduce the surrounding toxicity to a comfortable level, and researchers have begun noticing their skill at doing this. A team of scientists, led by Sanjay Kumar Dubey, isolated five species of cyanobacteria in India that were able to remove contaminants from pharmaceutical and textile wastewater. An experiment was set up to determine how well these species could remove those contaminants at various concentrations over the course of one week. Dubey and his team reported strong results: all contaminants were removed at both concentrations given enough time, which was generally no longer than a week.—Edward McLean
Dubey, S., Dubey, J., Mehra S., Tiwari, P., and Bishwas A. J. 2011 Potential use of cyanobacterial species in bioremediation of industrial effluents. African Journal of Biotechnology Vol. 10 (7), pp. 1125-1132
Dubey et al. set out to see how well isolated species of cyanobacteria could remove calcium, ammonia, nitrate, phosphorus, and several other metals and pollutants from textile and pharmaceutical effluents. They isolated the species and exposed them to different solutions of the effluents, some containing 5 ppm of pollutant and others with 10 ppm. They thought with some certainty that 10 ppm would be near the upward threshold of tolerance for these species and that some if not all of their metabolic pathways would shut down as a result, but to their surprise, the organisms cleaned up solutions that had 10 ppm more efficiently than those with 5 ppm. All five species were isolated into their own flasks to measure the effective rate of each one, but flasks containing mixtures of the five were also used in this experiment. The contaminated solutions that were exposed to multiple species were degraded fastest, leading Dubey et al. to believe that the most successful treatments for future study would use a mixture of cyanobacteria to remove contaminants rapidly. Measurements of the effluent were taken at 2, 4, and 7 days after the start of the experiment, and by the end of the week all treatments showed between a 97 – 99.7% removal efficiency of pollutants.
Dubey and his team’s findings are practically too good to be true. They demonstrate that the application of any of these five species, or a mixture, to a contamination source will result in extensive bioremediation of that pollution. Cyanobacteria are found practically anywhere that moisture or water is: from wet rocks to the ocean, these primitive, photosynthetic organisms grow and help recycle nutrients through the food-web, and our job now is determining which ones can be used in bioremediation. Because they are so wide-reaching and common, invasion or out-competing native species is less of a concern, so both in situ and ex situ management can take place with little worry about residual effects they might have on the surrounding, often unaffected, environment. The species this paper investigated have been shown to be beneficial in bioremediation projects, and while this type of work is perhaps the cheapest way of cleaning the environment, it can still be economically beneficial. The production of large quantities of these species will generate money for local industries and lead to growth in small communities. We’re still in the baby-steps phase of unlocking the potential of bioremediation, but I believe these kinds of bottom-up decontamination projects are the best way to remove pollution from our planet.