Antimicrobial Responses to Bacterial Metabolic Activity and Biofilm Formation Studied Using Microbial Fuel Cell-Based Biosensors

Abstract

Simultaneous monitoring of antimicrobial responses to bacterial metabolic activity and biofilm formation is critical for efficient screening of new anti-biofilm drugs. A microbial fuel cell-based biosensor using Pseudomonas aeruginosa as an electricigen was constructed. The effects of silver nanoparticles (AgNPs) on the cellular metabolic activity and biofilm formation of P. aeruginosa in the biosensors were investigated and compared with the traditional biofilm detection method. The crystal violet staining results showed that the concentration of AgNPs being increased to 20 and 40 μg/mL had a slight and obvious inhibitory effect on biofilm formation, respectively. In comparison, the detection sensitivity of the biosensor was much higher. When the concentration of AgNPs was 5 μg/mL, the output voltage of the biosensor was suppressed, and the inhibition gradually increased with the AgNPs dose. AgNPs inhibited the activity of planktonic cells in the anolyte and the formation of biofilm on the anode surface, and it had a dose-dependent effect on the secretion of phenazine in the anolyte. The biosensor could monitor the impacts of AgNPs not only on biofilm formation but also on cell activity and metabolic activity. It provides a new and sensitive method for the screening of anti-biofilm drugs.

Keywords: Pseudomonas aeruginosa; biosensor; microbial fuel cell; silver nanoparticles.

Figure 1

TEM image of silver nanoparticles.

Figure 2

The effects of different concentrations of silver nanoparticles on P. aeruginosa biofilm formation by the crystal violet staining method (n = 4); * p < 0.05, ** p < 0.01, and *** p < 0.001.

Figure 3

SEM images of P. aeruginosa biofilms on the cover glasses co-cultured with different concentrations of silver nanoparticles for 24 h.

Figure 4

The output voltage curves of MFC-based biosensors with P. aeruginosa co-cultured with different concentrations of silver nanoparticles.

Figure 5

The discharge curves of the original MFC, the MFC containing the original carbon brush anode in a fresh medium, and the MFC containing the original anolyte with a fresh carbon brush.

Figure 6

The cell activity of the planktonic cells co-cultured with different concentrations of silver nanoparticles in the anodic chamber of MFC-based biosensors (n = 6).

Figure 7

The amount of phenazine secreted by cells co-cultured with different concentrations of silver nanoparticles in the anodic chamber of MFC-based biosensors (n = 3).

Figure 8

The protein content of biofilms attached to carbon brush anodes with different concentrations of silver nanoparticles in the anodic chamber of MFC-based biosensors (n = 3); *** p < 0.001.

Figure 9

SEM images of P. aeruginosa biofilms on the anodes of MFC-based biosensors added with different concentrations of silver nanoparticles after 120 h.