Environmental pollution by plastic debris is estimated on a scale of 100 million metric tons, a portion of which is fragmented into micro-and nanoplastics. These fragments are often colonized by bacterial species in marine environments, possibly contributing to the biodegradation of such materials. However, further investigations are necessary to determine the impact of abiotic polymer weathering on biofilm adhesion, as well as the specific biofilm formation strategies employed by marine isolates. Here, we evaluate deep-sea sediment bacterial isolates for biofilm adhesion, extracellular matrix production, and polymer degradation ability. Our study focuses on high-density polyethylene (HDPE) fragments for their high durability and environmental persistence, subjecting fragments to abiotic weathering prior to bacterial colonization. Marine isolates identified as Pseudomonas sp. and Lysinibacillus sp. exhibited decreasing biofilm formation on weathered HDPE, especially over the first 24 h of incubation. This effect was countered by increased extracellular matrix production, likely improving cell adhesion to surfaces roughened by abiotic degradation. These adhesion strategies were contrasted with a reference Pseudomonas aeruginosa strain, which displayed high levels of biofilm formation on non-weathered HDPE and lower extracellular matrix production over the first 24 h of incubation. Furthermore, our results suggest that an increase in biofilm biomass correlated with changes to HDPE structure, indicating that these strains have a potential for biodegradation of plastic fragments. Therefore, this work provides a detailed account of biofilm formation strategies and bacteria-plastic interactions that represent crucial steps in the biodegradation of plastic fragments in marine environments.
In November 2015, two iron ore tailing dams collapsed in the city of Mariana, Brazil. The dams' collapse generated a wave of approximately 50 million m 3 of a mixture of mining waste and water. It was a major environmental tragedy in Brazilian history, which damaged rivers, and cities 660 km away in the Doce River basin until it reached the ocean coast. Shortly after the incident, several reports informed that the concentration of metals in the water was above acceptable legal limits under Brazilian laws. Here the microbial communities in samples of water, mud, foam, and rhizosphere of Eichhornia from Doce River were analyzed for 16S and 18S rRNA-based amplicon sequencing, along with microbial isolation, chemical and mineralogical analyses. Samples were collected one month and thirteen months after the collapse. Prokaryotic communities from mud shifted drastically over time (33% Bray-Curtis similarity), while water samples were more similar (63% Bray-Curtis similarity) in the same period. After 12 months, mud samples remained with high levels of heavy metals and a reduction in the diversity of microeukaryotes was detected. Amoebozoans increased in mud samples, reaching 49% of microeukaryote abundance, with Discosea and Lobosa groups being the most abundant. The microbial communities’ structure in mud samples changed adapting to the new environment condition. The characterization of microbial communities and metal-tolerant organisms from such impacted environments is essential for understanding the ecological consequences of massive anthropogenic impacts and strategies for the restoration of contaminated sites such as the Doce River.
Aims: Plastic debris are constantly released into oceans where, due to weathering processes, they suffer fragmentation into micro-and nanoplastics. Diverse microbes often colonize these persisting fragments, contributing to their degradation.However, there are scarce reports regarding the biofilm formation of eukaryotic decomposing microorganisms on plastics. Here, we evaluated five yeast isolates from deep-sea sediment for catabolic properties and early adhesion ability on high-density polyethylene (HDPE). Methods and Results:We assessed yeast catabolic features and adhesion ability on HDPE fragments subjected to abiotic weathering. Adhered cells were evaluated through Crystal Violet Assay, Scanning Electron Microscopy, Atomic Force Microscopy and Infrared Spectroscopy. Isolates were identified as Candida parapsilosis and exhibited wide catabolic capacity. Two isolates showed high adhesion ability on HDPE, consistently higher than the reference C. parapsilosis strain, despite an increase in fragment roughness due to weathering. Isolate Y5 displayed the most efficient colonization, with production of polysaccharides and lipids after 48 h of incubation. Conclusion:This work provides insights on catabolic metabolism and initial yeast-HDPE interactions of marine C. parapsilosis strains.Significance and Impact of the Study: Our findings represent an essential contribution to the characterization of early interactions between deep-sea undescribed yeast strains and plastic pollutants found in oceans.
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