In-situ detection based on the biofilm hydrophilicity for environmental biofilm formation

Abstract

A biofilm has a unique structure composed of microorganisms, extracellular polymeric substances (EPSs), etc., and it is layered on a substrate in water. In material science, it is important to detect the biofilm formed on a surface to prevent biofouling. EPSs, the major component of the biofilm, mainly consist of polysaccharides, proteins, nucleic acids, and lipids. Because these biomolecules have a variety of hydrophilicities or hydrophobicities, the substrate covered with the biofilm shows different wettability from the initial state. To detect the biofilm formation, this study employed a liquid-squeezing-based wettability assessment method with a simple wettability index: the liquid-squeezed diameter of a smaller value indicates higher wettability. The method is based on the liquid-squeezing behaviour of a liquid that covers sample surfaces when an air-jet is applied. To form the biofilm, polystyrene surfaces were immersed and incubated in a water-circulated bioreactor that had collected microorganisms in ambient air. After the 14-d incubation, good formation of the biofilm on the surfaces was confirmed by staining with crystal violet. Although the contact angles of captive bubbles on the surfaces with the biofilm were unmeasurable, the liquid-squeezing method could distinguish between hydrophilic and hydrophobic initial surfaces with and without biofilm formation using the diameter of the liquid-squeezed area. The surface wettability is expected to be a promising property for in-situ detection of biofilm formation on a macroscopic scale.

Simple Methods for Evaluating Acid Permeation and Biofilm Formation Behaviors on Polysiloxane Films

“…As ethanol reacts with the film when used as the solvent, pure water was used as a solvent for extracting crystal violet in this study. The use of pure water instead of ethanol as the solvent for extracting crystal violet can be one of the reasons for the greater variability than in biofilm quantification by crystal violet staining in previous studies [ 12 , 13 ].…”

Essential factors that affect bioelectricity generation by Rhodopseudomonas palustris strain PS3 in paddy soil microbial fuel cells

“…As shown in Figure 4E,F, many PS3 cells as well as microbial clumps were observed on the surface. It has been regarded that electrode ‐ associated microbial biofilms can facilitate the transport of electrons between electrodes and cells, as well as among cells fixed within the film for power generation of MFCs 10,41 . A few bacterial genera, such as Geobacter , Shewanella , Synechocystis , and Rhodopseudomonas , have been reported to transfer electrons through nanowires (pili and flagella) directly 12,26,42,43 .…”

“…It has been regarded that electrode-associated microbial biofilms can facilitate the transport of electrons between electrodes and cells, as well as among cells fixed within the film for power generation of MFCs. 10,41 A few bacterial genera, such as Geobacter, Shewanella, Synechocystis, and Rhodopseudomonas, have been reported to transfer electrons through nanowires (pili and flagella) directly. 12,26,42,43 We observed that there were several extracellular filamentous structures along with the PS3 cells during the SEM examination ( Figure 4B), which were proposed to function as nanowires.…”

Biological fixed‐film systems

“…EPS, one of the main components of biofilms, is composed of polysaccharides, proteins, nucleic acids, and lipids (Tanaka et al, 2019). Since EPS can diversely characterize in water (e.g., hydrophilic or hydrophobic), it presents variances in the wettability of biofilms.…”