Graphene-Based Nanomaterials Modulate Internal Biofilm Interactions and Microbial Diversity

Area of Science:

• Environmental Science
• Ecotoxicology
• Nanotechnology

Background:

• Graphene-based nanomaterials (GBMs) are produced at industrial scales, raising concerns about their environmental impact on microorganisms.
• Previous toxicity studies on GBMs used single species, failing to predict ecosystem-level consequences.
• Microorganisms form the base of the food chain, making their response to nanomaterials critical for ecosystem health.

Purpose of the Study:

• To assess the ecotoxicological effects of graphene oxide (GO) and reduced graphene oxide (rGO) on a diatom-Nitzschia palea and bacterial consortium biofilm.
• To compare the toxicity of GO and rGO on diatom physiology and bacterial community structure and metabolism.
• To evaluate the resilience of a microbial biofilm exposed to GBMs compared to single-species studies.

Main Methods:

• Exposure of a diatom-bacterial biofilm to GO and rGO at varying concentrations (0-10 mg.L^-1) for 48 and 144 hours.
• Assessment of diatom physiology using flow cytometry.
• Analysis of bacterial community structure via 16S amplicon sequencing and metabolic activity using Biolog ecoplates.

Main Results:

• Both GO and rGO stimulated diatom growth.
• GO inhibited bacterial growth at 1 mg.L^-1, altered bacterial community composition, and transiently increased carbon cycling activity, with minimal diatom toxicity.
• rGO showed weaker bacterial toxicity but stronger effects on diatom physiology.

Conclusions:

• Diatom-bacterial interactions within a biofilm confer resilience to GBM exposure.
• Biofilms can maintain or recover carbon-related metabolic functions despite GBM presence, unlike single-species responses.
• GBMs exhibit differential toxicity, with GO impacting bacteria more and rGO impacting diatoms more within the tested biofilm system.