Year-Long Microbial Succession on Microplastics in Wastewater: Chaotic Dynamics Outweigh Preferential Growth

Area of Science:

• Environmental microbiology
• Aquatic toxicology
• Polymer science

Background:

• Microplastics are pervasive aquatic pollutants.
• Understanding microbial interactions with microplastics is crucial.
• The concept of a 'plastisphere' (plastic-specific biome) is under investigation.

Purpose of the Study:

• To investigate the long-term microbial community dynamics on various microplastic types.
• To determine if a distinct plastic-specific microbiome (plastisphere) develops.
• To identify potential plastic-associated microbial taxa.

Main Methods:

• A year-long microcosm experiment exposing five microplastic types and silica beads to wastewater.
• Regular sampling (four times) over the year.
• 16S rDNA and ITS amplicon sequencing for bacterial and fungal community analysis.

Main Results:

• No evidence of a distinct plastisphere was found, even after one year.
• Microbial communities, especially bacterial, showed increasing dissimilarity between plastic types over time.
• A slight grouping of polyolefins (PE, PP) was observed in later-stage biofilms (6-12 months).
• The bacterial genus *Devosia* increased on plastics over time but not on silica controls, suggesting potential plastic association.

Conclusions:

• Long-term incubation is essential for observing microbial community dynamics on microplastics.
• A universal plastisphere does not appear to form readily.
• Specific polymers may influence microbial community structure, and certain taxa like *Devosia* may have a preference for plastic substrates.