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Free keywords:
plastisphere; plastic pollution; soil microbial community; microbial diversity; biofilms;
microbe–plastic interactions; polyethylene colonization; FESEM imaging
Abstract:
The concept of a ‘plastisphere microbial community’ arose from research on aquatic plastic
debris, while the effect of plastics on microbial communities in soils remains poorly understood.
Therefore, we examined the inhabiting microbial communities of two plastic debris ecosystems
with regard to their diversity and composition relative to plastic-free soils from the same area
using 16S rRNA amplicon sequencing. Furthermore, we studied the plastic-colonizing potential
of bacteria originating from both study sites as a measure of surface adhesion to UV-weathered
polyethylene (PE) using high-magnification field emission scanning electron microscopy (FESEM).
The high plastic content of the soils was associated with a reduced alpha diversity and a significantly
different structure of the microbial communities. The presence of plastic debris in soils did not
specifically enrich bacteria known to degrade plastic, as suggested by earlier studies, but rather
shifted the microbial community towards highly abundant autotrophic bacteria potentially tolerant
to hydrophobic environments and known to be important for biocrust formation. The bacterial
inoculates from both sites formed dense biofilms on the surface and in micrometer-scale surface
cracks of the UV-weathered PE chips after 100 days of in vitro incubation with visible threadlike
EPS structures and cross-connections enabling surface adhesion. High-resolution FESEM imaging
further indicates that the microbial colonization catalyzed some of the surface degradation of PE.
In essence, this study suggests the concept of a ‘terrestrial plastisphere’ as a diverse consortium
of microorganisms including autotrophs and other pioneering species paving the way for those
members of the consortium that may eventually break down the plastic compounds.
