Polluted seas: Bacteria really eat plastic
The bacterium Rhodococcus ruber eats and actually digests plastic. This has been shown in laboratory experiments by PhD student Maaike Goudriaan at Royal Netherlands Institute for Sea Research (NIOZ). “But,” Goudriaan emphasises, “this is certainly not a solution to the problem of the plastic soup in our oceans.
Goudriaan had a special plastic manufactured especially for these experiments with a distinct form of carbon (13C) in it. When she fed that plastic to bacteria after pretreatment with “sunlight” – a UV lamp – in a bottle of simulated seawater, she saw that special version of carbon appear as CO2 above the water. “The treatment with UV light was necessary because we already know that sunlight partially breaks down plastic into bite-sized chunks for bacteria,” the researcher explains. “This is the first time we have proven in this way that bacteria actually digest plastic into CO2 and other molecules,” Goudriaan states. It was already known that the bacterium Rhodococcus ruber can form a so-called biofilm on plastic in nature. It had also been measured that plastic disappears under that biofilm. “But now we have really demonstrated that the bacteria actually digest the plastic.”
No solution
When Goudriaan calculates the total breakdown of plastic into CO2, she estimates that the bacteria can break down about one percent of the available plastic per year. “That’s probably an underestimate,” she adds. “We only measured the amount of carbon-13 in CO2, so not in the other breakdown products of the plastic. There will certainly be 13C in several other molecules, but it’s hard to say what part of that was broken down by the UV light and what part was digested by the bacteria.” Even though marine microbiologist Goudriaan is very excited about the plastic-eating bacteria, she stresses that microbial digestion is not a solution to the huge problem of all the plastic floating on and in our oceans. “These experiments are mainly a proof of principle. I see it as one piece of the jigsaw, in the issue of where all the plastic that disappears into the oceans stays. If you try to trace all our waste, a lot of plastic is lost. Digestion by bacteria could possibly provide part of the explanation.”
More information can be found on the NIOZ website.
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