https://www.newscientist.com/article/mg23130931-000-lets-harness-synthetic-biology-to-fix-our-broken-planet/
Let’s harness synthetic biology to fix our broken planet By Ricard Solé MANY of us will have seen a lake covered in an algal bloom, the crystal clear surface transformed into a carpet of green, with a dark and suffocated body of water beneath. What’s fascinating about such an event is that it happens quickly – the lake reaches a tipping point and within a month the algae have taken over. This state isn’t permanent, however: lakes can be tipped back. Two decades ago, the ecologist Marten Scheffer showed that simply removing large predatory fish helps a lake regain its crystal clear state. It works because it allows the population of zooplankton to increase, and they eat the algae and stop the bloom. The method has been used around the world with great success. In the coming decades, climate change will mean many more ecosystems reaching catastrophic tipping points. Several grandiose suggestions have been made as to how we might engineer our way back from the brink, such as giant mirrors in space that would reduce the amount of solar energy reaching Earth. But such schemes are expensive and risky. My colleagues and I think we have a better idea, one that takes its cue from the solution to the algal blooms: engineering ecosystems using synthetic life. This approach could help prevent the spread of deserts, restore polluted lakes and rivers, attack the islands of plastic rubbish accumulating in the oceans, and deal with sewage or vast landfills resulting from industrial and farming activities. If done correctly, it would allow us to more easily predict and manage the consequences compared with proposals that would affect the entire globe. And best of all, the materials needed are essentially free. Synthetic biology is a well-established field. The basic premise is to treat an existing cell as a chassis and plug in chunks of genetic material that code for specific jobs, getting the cell to do new things without otherwise affecting it. To see how we might apply these principles to re-engineering a degraded environment, let’s take the example of desertification. Around 40 per cent of the world’s population lives in arid or semi-arid areas, and small changes in incoming sunlight, water or grazing can trigger a rapid shift into a desert. One way to avoid this is to encourage the growth of bacteria that naturally enhance moisture retention in the soil. Even a small improvement aids plant growth, which in turn provides nutrients for more bacteria, creating a virtuous circle that allows the system to escape the tipping point. But transplanting these bacteria from their natural habitat into another environment is quite a challenge. Just how difficult is reflected in the fate of the journal Microbial Releases. It launched in 1992 to publish accounts of experiments that put microbes into the ecosystem, but folded only two years later because so many of the tests failed. The problems boiled down to microbes being poorly adapted to survive in their new, unfamiliar environment. Release the genes We are in a better position today, thanks to synthetic biology. I think bacterial transplants should work much better if we take species that already live in arid soil, cyanobacteria for instance, and engineer them so that they produce a polymer that helps the soil retain water. This is still no mean feat, as it involves growing the bacteria in the lab and then moving them into the wild, two potentially very different environments. But it should be possible if we improve our understanding of the inner workings of cyanobacteria – and this is something my team in Barcelona is already looking into. Another approach, suggested by my colleagueVictor de Lorenzo, is to release a chunk of DNAinto the environment we wish to manage, so that species of bacteria living there can naturally incorporate it into their genome. These “genetic modules” are designed to spread through the population, and would provide instructions to enable any cell containing them to sense a physical or chemical property of their surroundings, and then produce chemicals to help steer those conditions towards a beneficial, stable state. For instance, and staying with the desertification example, they might equip whatever bacterium they enter to sense the level of moisture near it and produce a water-trapping polymer. But I can already hear the alarm bells ringing in your head. These ideas are bound to raise fears about the “Jurassic Park effect”: aren’t we attempting to manage systems that are too complex to control? There is good reason to be cautious about unintended consequences, but remember how high the stakes are. We are already experiencing a massive global extinction event and things will get worse not steadily, but suddenly, when we reach tipping points like those algae-infested lakes. What’s more, recent research has unearthed a few ways to control how widely our synthetic creations can propagate. For instance, it’s possible to give bacteria a suicide switch that automatically flicks once they stray outside boundaries that we define. This is already happening in non-natural environments.Hendrik Jonkers at Delft University of Technology in the Netherlands has developed a type of concrete impregnated with bacteria. When small cracks develop, the bacteria spring to life and produce calcium carbonate that repairs the damage. But the bacteria are designed so that they can’t survive outside the concrete – there is an ecological firewall. Something similar should be possible in natural environments, too. Take watercourses polluted with sewage. Bacteria designed to capture carbon dioxide or break down toxic chemicals could be added during waste treatment, and be programmed to switch off when they are washed into open water. As part of research project called Synterra, my collaborators and I are planning to think these ideas through more thoroughly and begin to test them. We are using computer simulations to better understand how synthetic bacteria would function in ecosystems, and we plan to use controlled outdoor plots to test the cyanobacteria I mentioned earlier. That may sound unpalatable, but let’s face facts. As recent debates over a new human-dominated geological epoch, the Anthropocene, we have been moulding the environment to our needs for centuries. We will inevitably keep doing that – so let’s do it right. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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