The “Plastisphere” of Biodegradable Plastics Is Characterized by Specific Microbial Taxa of Alpine and Arctic Soils

Abstract

Plastic pollution poses a threat to terrestrial ecosystems, even impacting soils from remote alpine and arctic areas. Biodegradable plastics are a promising solution to prevent long-term accumulation of plastic litter. However, little is known about the decomposition of biodegradable plastics in soils from alpine and polar ecosystems or the microorganisms involved in the process. Plastics in aquatic environments have previously been shown to form a microbial community on the surface of the plastic distinct from that in the surrounding water, constituting the so-called "plastisphere." Comparable studies in terrestrial environments are scarce. Here, we aimed to characterize the plastisphere microbiome of three types of plastics differing in their biodegradability in soil using DNA metabarcoding. Polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), and polyethylene (PE) were buried in two different soils, from the Swiss Alps and from Northern Greenland, at 15 • C for 8 weeks. While physico-chemical characteristics of the polymers only showed minor (PLA, PBAT) or no (PE) changes after incubation, a considerably lower α-diversity was observed on the plastic surfaces and prominent shifts occurred in the bacterial and fungal community structures between the plastisphere and the adjacent bulk soil not affected by the plastic. Effects on the plastisphere microbiome increased with greater biodegradability of the plastics, from PE to PLA. Copiotrophic taxa within the phyla Proteobacteria and Actinobacteria benefitted the most from plastic input. Especially taxa with a known potential to degrade xenobiotics, including Burkholderiales, Caulobacterales, Pseudomonas, Rhodococcus, and Streptomyces, thrived in the plastisphere of the Alpine and Arctic soils. In addition, Saccharimonadales (superphylum Patescibacteria) was identified as a key taxon associated with PLA. The association of Saccharibacteria with plastic has not been reported before, and pursuing this finding further may shed light on the lifestyle of this obscure candidate phylum. Plastic addition affected fungal taxa to a lesser extent since only few fungal genera such as Phlebia and Alternaria

Deep Soil Layers of Drought-Exposed Forests Harbor Poorly Known Bacterial and Fungal Communities

“…OTU abundances were normalized with the median of ratios method to account for differences in sequencing depth between samples. The statistical significance of the LFC was evaluated with Wald tests (Rüthi et al, 2020). P values were adjusted for multiple testing using the Benjamini-Hochberg method with a false discovery rate threshold of 5%.…”

The Terrestrial Plastisphere: Diversity and Polymer-Colonizing Potential of Plastic-Associated Microbial Communities in Soil

“…Besides ecological studies addressing the concept of a 'microbial plastisphere', the aim to discover microorganisms capable of degrading synthetic polymers has motivated a number of microbial studies in the last few years [15][16][17][18][19][20][21][22][23][24][25][26][27]. So far, microorganisms from more than 90 genera were found to possess plastic-degrading abilities [22].…”

“…Following the assumption that microbial communities in terrestrial habitats are substrate-dependent and influenced by their surrounding habitat [ 3 ], we hypothesize that plastic debris forms a selective habitat in soil in which the community structure is distinct from that of soil without a substantial plastic content. To our knowledge, there are in total six studies which examined plastic-associated microbial communities in soil using a next-generation sequencing approach [ 15 , 16 , 17 , 18 , 19 , 20 ]. While most of these studies found the plastic-associated microbial community to be less diverse when compared to the surrounding bulk soil [ 17 , 18 , 19 , 20 ], two studies reported a distinct microbial community on plastic debris in which a plastic-specific microbiota is enriched from the soil microbial community by the presence of plastic [ 15 , 16 ].…”

“…To our knowledge, there are in total six studies which examined plastic-associated microbial communities in soil using a next-generation sequencing approach [ 15 , 16 , 17 , 18 , 19 , 20 ]. While most of these studies found the plastic-associated microbial community to be less diverse when compared to the surrounding bulk soil [ 17 , 18 , 19 , 20 ], two studies reported a distinct microbial community on plastic debris in which a plastic-specific microbiota is enriched from the soil microbial community by the presence of plastic [ 15 , 16 ]. Thus, how far soil-buried plastic debris selects for a specific microbial community composition still remains poorly understood.…”

From plastic mulching to microplastic pollution : An effect assessment of microplastics in the soil-plant system

“…Secondly, carbon supplied by Bio-MPs (such as PBAT, PLA and PHA) has can be utilized by microorganisms to gain biomass and energy (Urtuvia et al, 2014;Zumstein et al, 2018b). However, by gaining access to this bioavailable-C source, these microorganisms might outcompete microorganisms who are unable to metabolize this carbon source (Dini-Andreote et al, 2015;Rüthi et al, 2020), thus lowering microbial diversity at 2.5% Bio-MPs.…”