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| Confocal laser scanning microscopy image of the plastisphere collected from plastic waste in the Pacific Ocean. The image shows the biological components that coexist in close proximity within the plastisphere: green – bacteria, blue – algae, red – extracellular sugar matrix, white – fungal hyphae. Photo Credit: Dr Thomas Neu/UFZ |
Scientific Frontline: Extended "At a Glance" Summary: The Plastisphere
The Core Concept: The "plastisphere" is a novel marine ecosystem composed of a diverse community of microorganisms—including bacteria, viruses, fungi, and algae—that colonize and thrive on the persistent plastic particles polluting the world's oceans.
Key Distinction/Mechanism: Unlike naturally occurring marine plankton, which have evolved reduced genomes suited for nutrient-poor pelagic environments, microbes in the plastisphere possess significantly larger genomes with multiple functional gene copies. This biological adaptation allows the plastisphere biofilm to efficiently absorb nutrients, repair ultraviolet radiation damage, and utilize shared metabolic pathways, effectively creating localized, nutrient-rich niches in the open ocean.
Major Frameworks/Components:
- Metagenomic Sequencing: Analyzing the total environmental DNA of biological communities residing on ocean macroplastics to compare their structural and functional composition against naturally occurring plankton.
- Functional Gene Analysis: The examination of approximately 340 key functional genes responsible for nutrient uptake, carbon degradation, and rapid genomic repair mechanisms.
- Alternative Energy Utilization: The capacity of plastisphere microbes to employ alternative energy strategies, such as anoxygenic photosynthesis, to survive the extreme conditions of the ocean surface.
- Biomass Potential: The detection of elevated chlorophyll a concentrations, indicating that the biofilm has the potential to generate comparatively more biomass than surrounding plankton communities.
Branch of Science: Environmental Science, Marine Microbiology, Ecotoxicology, and Metagenomics.
Future Application: While researchers note that these microorganisms use plastic as a habitat rather than a food source (making them unlikely candidates for eliminating oceanic plastic waste), understanding their robust genetic frameworks could inform future biotechnological applications in carbon metabolism, ultraviolet resistance, and cellular repair strategies. Furthermore, studying these biofilms aids in modeling complex disruptions to marine geochemical cycles.
Why It Matters: The proliferation of the plastisphere signifies a profound and unnatural alteration of marine environments. Because these adapted microbes create artificial eutrophic (nutrient-rich) zones and exhibit functional advantages over natural plankton, their existence threatens to permanently disrupt the sensitive ecological balance and baseline health of the global ocean system.
Plastic pollution is a global problem. It damages ecosystems, endangers animals, and in the form of nanoplastic particles can also have consequences for human health. A global agreement to regulate plastic pollution is therefore long overdue. However, plastic particles have also become a new habitat for bacteria, viruses, fungi, and algae. The ecological significance of this ‘plastisphere’ for natural communities is the subject of numerous research projects. In this study, for example, researchers from the Helmholtz Centre for Environmental Research (UFZ) and the GEOMAR Helmholtz Centre for Ocean Research Kiel have examined bacterial metagenomes. The results show that the genomes of microbes in the plastisphere are larger and contain more gene copies associated with functional processes than those of marine plankton. This adaptation ensures their survival; the researchers write in Environmental Pollution.
Trillions of persistent plastic particles of varying sizes are scattered throughout the world’s oceans, where they often accumulate in ocean gyres known as ‘garbage patches’. Two of these regions were the focus of research expeditions by Helmholtz researchers in 2019. As part of the MICRO-FATE project led by the UFZ researchers aboard the research vessel SONNE analyzed plastic particles in the North Pacific Garbage Patch between Singapore and Canada while colleagues from the GEOMAR Helmholtz Centre for Ocean Research Kiel aboard the research vessel POSEIDON as part of the PLASTISEA project investigated the North Atlantic Garbage Patch southwest of the Azores. “From a taxonomic perspective, the plastisphere has been well studied. Less is known, however, about the functional strategies that enable microorganisms in the biofilm to survive the extreme conditions of a nutrient-poor environment and high UV exposure at the ocean’s surface”, says UFZ hydrobiologist and co-author Dr Mechthild Schmitt-Jansen.
During their ocean expeditions, the researchers collected macroplastics from the ocean surface and extracted DNA from the plastisphere. They then sequenced their metagenomes – that is the total DNA of a biological community – and compared the structure and function of microbial metagenomes of the plastisphere in the Pacific and Atlantic oceans with that of plankton naturally occurring in the sea. The analyses focused on functional genes. These sections of DNA encode important functions for organisms and thus form the basis of biological processes. “Functional genes contain genetic information that enables microbes to produce proteins, control metabolic processes, build cell structures, and regulate signaling processes within the cell”, says GEOMAR microbiologist and co-author Dr Erik Borchert.
In their analysis of around 340 key functional genes, Helmholtz researchers found that the bacterial metagenome of the plastisphere differs considerably from natural plankton communities in the Pacific and Atlantic in terms of both structure and function. The metagenome thus contains more of those functional genes that enable microbes in the plastisphere to survive under the extreme conditions of the open oceans. “The microorganisms in the biofilm have more gene copies, thereby enabling them to absorb nutrients effectively, utilize and break down carbon sources, and either ward off UV radiation through effective mechanisms or repair damage to the genome quickly”, says UFZ biologist and lead author Dr Stefan Lips. They can also use alternative energy sources such as anoxygenic photosynthesis, which does not produce oxygen.
Differences were also observed in the taxonomic structure of the biofilm: although the species composition within the bacterial groups differs between the Atlantic and the Pacific, the functionally relevant bacterial groups are comparable in both oceans.
The research team also found that the genomes of microbes in the plastisphere are considerably larger than those of naturally occurring marine plankton. Over the course of evolution, plankton has adapted their genomes to nutrient-poor environments and greatly reduced their genome size. The microbes in the plastisphere do not need to do this because they benefit from the shared metabolic processes of the microorganisms on the plastic particles – and thus from a better availability of nutrients. Furthermore, relatively high concentrations of chlorophyll a were found in the biofilm compared with plankton. “This shows that, in relative terms, microbes in the plastisphere have the potential to produce more biomass than the surrounding plankton”, says Schmitt-Jansen. “This creates eutrophic niches in the nutrient-poor environment of the open oceans”.
The research results show how microorganisms in the plastisphere adapt to the harsh living conditions in nutrient-poor subtropical ocean gyres. “This is not a good sign for the oceans, because only their original, natural state is considered healthy – and any deviation from that is seen as a deterioration”, says Lips. Whether biofilm growth on plastic disrupts the geochemical cycles of these sensitive ecosystems remains a subject of ongoing research. “Because microbes use plastic as a habitat rather than a source of nutrients, it is unlikely that they will help to remove plastic from the oceans”, says Borchert. That is why it is imperative that we put a stop to plastic pollution as soon as possible.
Funding: This collaborative study by the UFZ and GEOMAR was conducted as part of the InnoPool projectsP-LEACH and AI MareExplore and was funded by the Helmholtz Association and the BMFTR projects MICRO-FATE and PLASTISEA.
Published in journal: Environmental Pollution
Title: Metagenomic analyses of the plastisphere reveals a common functional potential across oceans
Authors: Stefan Lips, Mechthild Schmitt-Jansen, and Erik Borchert
Source/Credit: Helmholtz Centre for Environmental Research
Reference Number: env040926_01
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