Effects of Nanoplastics on Freshwater Biofilm Microbial Metabolic Functions as Determined by BIOLOG ECO Microplates

Abstract

Nanoplastic (NP) contamination is becoming a pervasive issue as NPs, originating from microplastic particles, pose potentially harmful environmental impacts on aquatic ecosystems. The environmental hazards of NPs on microorganisms have been well documented in recent studies; however, little is known about their ecotoxicity effects on freshwater biofilms, which serve as important primary producers and decomposers and are highly connected with other ecosystem components. We investigated the effects of NPs on the microbial metabolic functions of freshwater biofilms in terms of carbon source utilization ability. Biofilm samples were collected, cultivated in a hydrodynamic flume for six weeks, and then exposed in polystyrene (PS) beads (100 nm in size) with different NP concentrations (1, 5, and 10 mg/L). BIOLOG ECO microplates were used to quantify carbon source utilization characteristics. The data were analyzed using average well-color development (AWCD), functional diversity indices, and principle component analysis (PCA). Results showed that the total carbon metabolic functions (represented by AWCD) remained constant (p > 0.05) with elevated NP concentrations, but some specific carbon sources (e.g., esters) changed in their utilization ability (p < 0.05). The microbial functional diversity (Shannon–Wiener diversity index, Simpson diversity index, and Shannon evenness index) was significantly reduced under 10 mg/L NPs (p < 0.05), indicating an inhibiting effect of NPs on biofilm metabolic diversity. This study examined NP ecotoxicity effects on microbial metabolic activities at the community level, but further studies are required to fully understand the mechanisms driving this change.

Microbial Carbon Metabolic Functions in Sediments Influenced by Resuspension Event

“…Next, the suspension was added into the wells (150 µL) of the BIOLOG ECO microplate, and incubated at 25 • C for 7 days [50]. During the incubation, the absorbance value was determined at 590 every 12 h using a multifunctional enzyme label tester (Bio Tek, Winooski, VT, USA) for 7 to 10 days, and based on previous studies [51][52][53][54].…”

“…Generally, the utilization of carbon sources was positively correlated with the meta bolic capacity of the corresponding microorganisms, which could be characterized b AWCD [51]. At present, the Biolog profiles are generally referred as Community Leve Physiological Profiles (CLPP) and have been widely used to explore the carbon metabo lism and degradation activity of microorganisms [ As shown in Figure 2c, in G1 and G2, there were significant differences between the COD concentrations of the G1 and G2 treatment groups during the whole test period (p < 0.05), and there was significant difference between the final value and initial value of COD concentration in the G1 and G2 treatment groups (p < 0.05).…”

“…Generally, the utilization of carbon sources was positively correlated with the metabolic capacity of the corresponding microorganisms, which could be characterized by AWCD [51]. At present, the Biolog profiles are generally referred as Community Level Physiological Profiles (CLPP) and have been widely used to explore the carbon metabolism and degradation activity of microorganisms [52,[59][60][61].…”

Distinct Responses of Biofilm Carbon Metabolism to Nanoplastics with Different Surface Modifications

“…Average well color development (AWCD) was measured using BIOLOG ECO microplates (Hayward, CA, USA) (see Supplementary Material SI ), which can be used to assess the ability of microbes to metabolize carbon sources. The details were given in our previous study [ 16 ]. Briefly, the biofilm samples were suspended and ultrasonicated.…”

“…In addition, Lu et al found that a low concentration (10 mg/L) of 100 nm plastic particles inhibited the reproduction of Chlorella pyrenoidosa, while a high-concentration (100 mg/L) exposure significantly increased the reproduction rate [ 15 ]. Previously, Guo et al studied the effect of nano-PS beads with different concentrations (1, 5 and 10 mg/L) on freshwater biofilm microbial metabolic functions [ 16 ], and Miao et al studied the acute effects of nano-PS beads with different particle sizes and concentrations on the functional enzymes of periphytic biofilms [ 10 ]. However, there is limited information about the effects of nanoplastics with different surface modifications on the microbial functions of freshwater biofilms.…”