Journal of Bioremediation & Biodegradation
Open Access

Electrical conductivity; Extracellular electron transfer; Ion transport; Microbial species; Bioelectrochemical systems; Wastewater treatment; Metabolic processes

Introduction

Biofilms, which are dense clusters of microorganisms encased in a self-produced extracellular matrix, are ubiquitous in both natural and engineered environments. These biofilms can form on diverse surfaces, including medical devices, wastewater treatment facilities, and industrial pipelines, and they play a crucial role in microbial ecology and biogeochemical cycles [1]. An intriguing feature of biofilms is their ability to conduct electricity, a property that is not typically associated with individual planktonic cells. Electrical conductivity in biofilms can result from a range of mechanisms, most notably extracellular electron transfer (EET), ion transport across the biofilm matrix, and the metabolic interactions between microorganisms within the biofilm. The conductivity of biofilms has garnered considerable attention in recent years due to its implications for biotechnological and environmental applications [2]. Biofilms are central to the development of bioelectrochemical systems (BES), which leverage microbial metabolic activities to generate electricity or facilitate the treatment of wastewater. Furthermore, biofilm conductivity plays a pivotal role in processes like corrosion, where microbial-induced biofilms contribute to the deterioration of materials in industrial settings. In this review, we aim to provide an in-depth examination of the mechanisms governing biofilm conductivity, the factors influencing this property, and the wide range of applications where biofilms' conductive properties can be harnessed [3]. We will also explore the challenges in studying and manipulating biofilm conductivity and propose future directions for advancing research in this exciting and promising field.

Discussion

The electrical conductivity of biofilms is a multifaceted phenomenon, influenced by various biological, chemical, and physical factors. Central to the conductivity of biofilms is the process of extracellular electron transfer (EET), which allows microorganisms to exchange electrons with extracellular surfaces, including electrodes or metals [4]. This mechanism is critical in bioelectrochemical systems (BES), where biofilms facilitate electron flow, enabling processes such as microbial fuel cells (MFCs) and microbial electrolysis cells (MECs). The microbial species within a biofilm significantly affect its conductivity, with some bacteria exhibiting a higher capacity for electron transfer than others, often through conductive pili (nanowires), outer membrane cytochromes, or by reducing metal ions in the extracellular matrix. Environmental factors, such as nutrient availability, oxygen concentration, pH, and temperature, also play a substantial role in determining the electrical properties of biofilms [5]. In particular, nutrient limitation can lead to a shift in the microbial community structure, influencing biofilm formation and its conductive characteristics. Moreover, biofilm thickness and density, which change over time during biofilm development, can impact ion transport and the overall conductivity of the system.

In addition to the basic mechanisms of conductivity, the implications of biofilm conductivity are profound across various industries [6,7]. In wastewater treatment, biofilms enhance the efficiency of microbial electrochemical processes by accelerating electron transfer and improving the degradation of organic pollutants. The conductivity of biofilms also aids in enhancing the performance of microbial fuel cells, which hold promise for sustainable energy generation through the conversion of organic waste into electrical energy [8]. However, the role of biofilms in corrosion presents a challenge, as biofilms in industrial pipelines can contribute to material degradation, a process exacerbated by microbial electrochemical interactions. Despite the potential, several challenges remain in exploiting biofilm conductivity for large-scale applications. One major obstacle is the variability of conductivity in biofilms due to differences in microbial composition, growth conditions, and environmental factors. Standardizing biofilm conductivity for reproducibility and efficiency in industrial settings remains a significant challenge [9,10]. Furthermore, biofilm-related issues such as biofouling, which is the unwanted accumulation of biofilms on surfaces, can hinder the performance of systems where biofilm conductivity is desired, such as in water purification systems and fuel cells.

Conclusion

The electrical conductivity of biofilms is a promising but complex area of research with vast potential in biotechnological and industrial applications. The mechanisms of extracellular electron transfer, ion transport, and microbial interactions within biofilms provide a foundation for understanding their conductive properties. As demonstrated, biofilms can be leveraged in bioelectrochemical systems for energy production, wastewater treatment, and other environmental applications. However, challenges remain in controlling and optimizing biofilm conductivity for practical use. Future research should focus on enhancing our understanding of the factors that influence conductivity at the microbial level and developing strategies to manipulate biofilm properties in a predictable manner. Innovations in material science, such as conductive substrates or engineered biofilms, could provide new avenues for improving biofilm conductivity in real-world applications. Ultimately, harnessing the electrical conductivity of biofilms offers an exciting frontier in sustainable technology, but more work is required to overcome the current limitations and unlock their full potential in various industrial processes.

Acknowledgement

None

Conflict of Interest

None