(SPOT.ph) Every day, we see plastic bags everywhere. And while it's sometimes hard to see the grand scheme of things, plastic pollution is one of the factors causing the current climate crisis—and, ultimately, resulting in erratic weather, flooding and landslide, and threat to food security. So scientists are now in a race to figure out what to do with all the plastics, especially those found in our waters. In a December 2022 paper published in a Germany-based peer-reviewed scientific journal, University of the Philippines - Marine Science Institute researchers Norchel Gomez and Dr. Deo Onda observed that plastic-eating bacteria may actually exist in Manila Bay.
The Science Behind Plastic-Eating Bacteria
Microorganisms, from the name itself, are organisms that are too small that the only way to see them is under a microscope. Sometimes called microbes, microorganisms can be bacteria, fungi, algae, protozoa, and viruses. Bacteria, most especially, break down dead organisms, animal waste, and plant litter—from which they use the elements as nutrients. They are everywhere, thriving at the bottom of the food chain, feeding off anything—including plastics in the ocean.
"Our study has observed partial degradation activity of potential plastic-eating bacteria in Manila Bay sediments for low-density polyethylene," Gomez tells SPOT.ph.
Low-density polyethylene (LDPE) is your usual plastic labo and plastic bags, which are abundant in Philippine waters, including Manila Bay. When a piece of plastic is released into the waters, microorganisms treat it as a habitat and even make a whole marine ecosystem out of it. Scientists started calling this human-made plastic environment a "plastisphere."
Related to this, there is increasing evidence that plastics that have been around for a long time in marine habits appear to have signs of deterioration and decomposition, which can only mean that microorganisms have something to do with their breakdown.
Plastic-Eating Bacteria in Manila Bay
Gomez and Onda, for their part, looked in our backyard: Manila Bay, which is known to be heavily polluted by plastics, especially since it serves as a catch basis of many rivers in and around Metro Manila. In fact, the Pasig River was found to be the world's biggest source of ocean plastic waste in a 2021 study.
Their team looked at five coastal sites on the southern coast of Manila Bay: Ternate, Naic, Noveleta, Las Piñas-Parañaque Critical Habitat and Ecotourism Area, and Baseco (Manila). Because of the varied activities in these areas, different types of plastic and plastic accumulation can also be studied.
Baseco, for example, is densely populated; Las Piñas-Parañaque Critical Habitat and Ecotourism Area, while near a residential area, is home to planted mangroves, fishes, and mollusks; and the sites in Cavite provide a mix of urban and rural residential spaces. In these sampling sites, low-density polyethylene was found to be the most abundant, especially the plastic bags from the local supermarket.
For the study, they took samples of Manila Bay water, which have all the microbial goodness, and simulated how it can affect a measured sheet of plastic bag. Various changes were monitored, from the plastic's weight before and after the process to other biochemical properties.
"We say 'partial' degradation since we haven’t tested for the complete biodegradation process. Instead, we investigated the first two processes - biodeterioration and depolymerization. The two succeeding processes are assimilation and remineralization, after which a complete biodegradation process is done. However, analysis of these two processes would need sophisticated equipment for testing. A follow-up study by another researcher in the lab, Justine Bitalac, was able to isolate and purify and culture these biodegrading bacteria. Having these bacteria in culture will allow researchers to look closely at the mechanisms and processes involved in the biodegradation of plastics," Gomez tells us.
In simple words, yes, microorganisms in Manila Bay eat plastics, to put it bluntly.
Plastic-Eating Bacteria Is Not the Answer
While this observation of microorganisms feeding off plastics is becoming more and more common, microorganisms just don't have a choice on what to eat.
"Microbes are opportunistic organisms that are capable of adapting to an environment as long as bioavailable resources or their preferred food are accessible," Gomez explains.
Eating plastic doesn't affect them directly, but since plastic is synthetic, the other processes they're involved with in the environment may be affected. Microbes, after all, are part of why the soil has nitrogen—which is used by plants to grow, carbon dioxide and methane in the air, and so on. Just think about how these essential elements in nature are affected when you put plastic in the equation.
"Although the plastics may ‘disappear’ from sight, they will just be converted back to other forms, such as carbon dioxide. Bio-fragmentation of the plastic during degradation also leads to the production of smaller plastics called microplastics, which pose another threat to the food chain. Moreover, since plastics are transported across far distances in the marine environment, pathogens within the microbial communities attached to the plastic surface may also be transferred to other ecosystems and infect vulnerable organisms," adds Gomez.
The UP scientists clarified that plastic biodegradation is only a portion of the solutions being explored amid the world's plastic pollution problem. As an example, Gomez explained how a related study in Japan took 15 years just to study how and how long a specific enzyme can break down a plastic bottle. "The work we’ve done is probably just 1/20 of the total work that needs to be done, which means we still have a long way to go."
If the world experts' projection that there will be more plastic than fish in the oceans by 2050 is true, we just don't have enough time to figure out if a microorganism can actually eat one small piece of plastic. The positive developments in plastic biodegradation are significant, but it's not a solution to plastic pollution. The most it can do is "understand the fate of plastics in the environment," which will not make the problem disappear overnight, but at least, allow us to produce alternative materials.
"The burden of coming up with solutions should not be carried solely by scientific research because the plastics problem is a multi-stakeholder issue. The earth would only heal itself if we take steps towards turning off the tap, which should begin with reducing plastic production and urging manufacturing companies to explore biodegradable alternatives for different plastic types," Gomez concluded.
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For more information, read Potential of sediment bacterial communities from Manila Bay (Philippines) to degrade low-density polyethylene (LDPE) by Norchel Gomez and Dr. Deo Onda (Archives of Microbiology 205:38, December 2022).