#FEMSmicroBlog: Marine microbes – the potential for a greener, cleaner future

08-06-2022

Millions of tons of plastic enter the oceans every year. The constant growth of global plastic production along with the lack of sufficient waste management will only lead to increasing plastic contamination. For this year’s World Ocean Day, Eva Sonnenschein explains for the #FEMSmicroBlog how we could use oceanic microorganisms to help understand and relieve our global plastic pollution problem. #MicrobiologyEvents

 

What happens to plastic in the environment?

Plastic has been introduced to the environment since about the mid-last century. However, we only started asking the question “what is the fate of plastic in the environment?” about 20 years ago. Today, we know that this durable material is fragmented into smaller pieces by abiotic processes. This leaves us with so-called microplastics and nanoplastics floating around the environment.

New analytical tools and mathematical models have helped explain how plastic is being transported in the environment. Interestingly, a major mismatch exists in the estimated amount of plastic entering the marine systems and the actually >250,000 metric tons that were measured in the surface oceans.

Several factors might contribute to this discrepancy including floating polymers in the plastic as well as biofouling (colonization) and biodegradation (breakdown) by marine microorganisms.

 

Microbes eating plastic waste

In terrestrial systems, plastic-degrading microorganisms have indeed been identified. For example, the bacterium Ideonella sakaiensis produces the enzyme PETase that degrades the plastic polyethylene terephthalate (PET). Since the discovery of this promising candidate in 2016, the PETase enzyme has been optimized by bioengineering and has even gone into industrial production.

But tackling our plastic waste problem requires us to identify additional tools and approaches. For this, researchers looked into oceanic environments as these harbor a huge diversity of microbes and metabolic potential.

Interestingly, marine microorganisms, including bacteria and microalgae, can readily attach to and colonize virgin plastic. These plastic biofilms contain a unique microbial composition compared to that of the surrounding environment. For example, some bacterial families, including Erythrobacteraceae or Oceanospirillales, seem to re-occur on marine plastic across the oceanic systems.

Marine bacteria colonize plastic. From Hansen et al. (2021).

Based on metagenomic datasets from the marine environment, researchers then found promising protein sequences that share high similarities to known plastic-degrading enzymes. Also, strains from the Erythrobacteraceae or Oceanospirillales families showed hydrocarbonoclastic activities, meaning they could live off the hydrocarbons in plastics as carbon and energy sources.

Additionally, some marine microbial groups have the metabolic potential to not only live on plastic but also degrade it. Hence, the marine microbiota might provide us with novel tools to reduce plastic waste in our environment.

 

Oceanic microbes rescuing us from plastic waste?

With huge amounts of plastic present in the environment, we know that decreasing our plastic pollution will not be easy. This is primarily due to the slow degradation rates of microbial enzymes. So, also for the microbial degraders, the biodegradation of plastic is indeed a challenging process.

Secondly, in Nature, microbes always interact with each other and so far we do not understand the full picture of these microbial networks. It might require highly specialized enzymatic machineries or the interplay of several microbial players and abiotic processes to degrade hydrophobic polymers with high molecular weight.

However, protein and metabolic engineering are constantly advancing and we keep learning about the metabolic capabilities of marine microorganisms. Hopefully, we will be able to establish biotechnological systems that will lead to new plastic waste management strategies in the near future.

For this year’s World Ocean Day, let’s not only think about how to improve the ocean’s health but also how oceanic players might improve the planet’s health.

 

About the author

Eva Sonnenschein studies how marine bacteria and microalgae interact and how these organisms and their molecules can be used for sustainable, biotechnological applications. She is currently Senior Researcher at the Technical University of Denmark and starting as Associate Professor at Swansea University in September 2022.

About this blog section

The section #MicrobiologyEvents for the #FEMSmicroBlog reports about events and meetings relevant to our network. These include world awareness days, FEMS-sponsored meetings or meetings of Member Societies and many more.

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