Physiological Benefits of Oxygen-Terminating Extracellular Electron Transfer

Oxygen microenvironments in Escherichia coli biofilm nutrient transport channels: insights from complementary sensing approaches

Chemical gradients and the emergence of distinct microenvironments in biofilms are vital to the stratification, maturation and overall function of microbial communities. These gradients have been well characterized throughout the biofilm mass, but the microenvironment of recently discovered nutrient transporting channels in Escherichia coli biofilms remains unexplored. This study employs three different oxygen sensing approaches to provide a robust quantitative overview of the oxygen gradients and microenvironments throughout the biofilm transport channel networks formed by E. coli macrocolony biofilms. Oxygen nanosensing combined with confocal laser scanning microscopy established that the oxygen concentration changes along the length of biofilm transport channels. Electrochemical sensing provided precise quantification of the oxygen profile in the transport channels, showing similar anoxic profiles compared with the adjacent cells. Anoxic biosensing corroborated these approaches, providing an overview of the oxygen utilization throughout the biomass. The discovery that transport channels maintain oxygen gradients contradicts the previous literature that channels are completely open to the environment along the apical surface of the biofilm. We provide a potential mechanism for the sustenance of channel microenvironments via orthogonal visualizations of biofilm thin sections showing thin layers of actively growing cells. This complete overview of the oxygen environment in biofilm transport channels primes future studies aiming to exploit these emergent structures for new bioremediation approaches.

Photoelectron Therapy Preventing the Formation of Bacterial Biofilm on Titanium Implants

The exogenous bacterial infection and formation of biofilm on the surface of titanium implants can affect the adhesion, proliferation, and differentiation of cells associated with osteogenesis, ultimately leading to surgical failure. This study focuses on two critical stages for biofilm formation: i) bacterial adhesion and aggregation, ii) growth and proliferation. The titanium with well-organized titania nanotube arrays is first modified by nitrogen dopants, then loaded with CuFeSe2 nanoparticles to form a p-n heterojunction. Such heterojunction can effectively separate the electrons and holes generated by CuFeSe2 under NIR excitation, where CuFeSe2 serves as an electron acceptor from adherent bacteria, thus disrupting the respiratory chain and eventually affecting the metabolism. Combined with the released ions in solution and photothermal effect, the formation of bacterial biofilm on the surface of titanium implants is prevented on both stages.

Perspectives on the future of ecology, evolution, and biodiversity from the Council on Microbial Sciences of the American Society for Microbiology

The field of microbial ecology, evolution, and biodiversity (EEB) is at the leading edge of understanding how microbes shape our biosphere and influence the well-being of humankind and Earth. To that end, EEB is developing new transdisciplinary tools to analyze these ecologically critical, complex microbial communities. The American Society for Microbiology's Council on Microbial Sciences hosted a virtual retreat in 2023 to discuss the trajectory of EEB both within the Society and microbiology writ large. The retreat emphasized the interconnectedness of microbes and their outsized global influence on environmental and host health. The maximal potential impact of EEB will not be achieved without contributions from disparate fields that unite diverse technologies and data sets. In turn, this level of transdisciplinary efforts requires actively encouraging "broad" research, spanning inclusive global collaborations that incorporate both scientists and the public. Together, the American Society for Microbiology and EEB are poised to lead a paradigm shift that will result in a new era of collaboration, innovation, and societal relevance for microbiology.

Multi-dimensional perspectives into the pervasive role of microbial extracellular polymeric substances in electron transport processes

During the process of biological treatment, most microorganisms are encapsulated in extracellular polymeric substances (EPS), which protect the cell from adverse environments and aid in microbial attachment. Microorganisms utilize extracellular electron transfer (EET) for energy and information interchange with other cells and the outside environment. Understanding the role of steric EPS in EET is critical for studying microbiology and utilizing microorganisms in biogeochemical processes, pollutant transformation, and bioenergy generation. However, the current study shows that understanding the roles of EPS in the EET processes still needs a great deal of research. In view of recent research, this work aims to systematically summarize the production and functional group composition of microbial EPS. Additionally, EET pathways and the role of EPS in EET processes are detailed. Then factors impacting EET processes in EPS are then discussed, with a focus on the spatial structure and composition of EPS, conductive materials and environmental pollution, including antibiotics, pH and minerals. Finally, strategies to enhance EET, as well as current challenges and future prospects are outlined in detail. This review offers novel insights into the roles of EPS in biological electron transport and the application of microorganisms in pollutant transformation.

In Situ Self-Growth of a ZnO Nanorod Array on Nonwoven Fabrics for Empowering Superhydrophobic and Antibacterial Features

ZnO nanorod nonwoven fabrics (ZNRN) were developed through hydrothermal synthesis to facilitate the prevention of the transmission of respiratory pathogens. The superhydrophobicity and antibacterial properties of ZNRN were improved through the response surface methodology. The synthesized material exhibited significant water repellency, indicated by a water contact angle of 163.9°, and thus demonstrated antibacterial rates of 91.8% for Escherichia coli (E. coli) and 79.75% for Staphylococcus aureus (S. aureus). This indicated that E. coli with thinner peptidoglycan may be more easily killed than S. aureus. This study identified significant effects of synthesis conditions on the antibacterial effectiveness, with comprehensive multivariate analyses elucidating the underlying correlations. In addition, the ZnO nanorod structure of ZNRN was characterized through SEM and XRD analyses. It endows the properties of superhydrophobicity (thus preventing bacteria from adhering to the ZNRN surface) and antibacterial capacity (thus damaging cells through the puncturing of these nanorods). Consequently, the alignment of two such features is desired to help support the development of personal protective equipment, which assists in avoiding the spread of respiratory infections.

A self-activating electron transfer antibacterial strategy: Co3O4/TiO2 P-N heterojunctions combined with photothermal therapy

Implant-associated infections are significant impediments to successful surgical outcomes, often resulting from persistent bacterial contamination. It has been hypothesized that bacteria can transfer electrons to semiconductors with comparable potential to the biological redox potential (BRP). Building on this concept, we developed an antibiotic-free bactericidal system, Co3O4/TiO2-Ti, capable of achieving real-time and sustainable bactericidal effects. Our study demonstrated that Co3O4/TiO2-Ti, possessing an appropriately set valence band, initiated charge transfer, reactive oxygen species (ROS) production, and membrane damage in adherent Staphylococcus aureus (S. aureus). Notably, in vivo experiments illustrated the remarkable antibacterial activity of Co3O4/TiO2-Ti, while promoting soft-tissue reconstruction and demonstrating excellent cytocompatibility. Transcriptomic analysis further revealed a down-regulation of aerobic respiration-associated genes and an up-regulation of ROS-associated genes in S. aureus in the presence of Co3O4/TiO2-Ti compared to Ti. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and gene set enrichment analysis (GSEA) identified alterations in respiratory metabolism, oxidative phosphorylation, and the synthesis of amino acid in S. aureus cultured on Co3O4/TiO2-Ti. Furthermore, when combined with near-infrared (NIR) irradiation and photothermal therapy (PTT), Co3O4/TiO2-Ti eliminated 95.71% of floating and adherent S. aureus in vitro. The findings suggest that this antibiotic-free strategy holds substantial promise in enhancing implant sterilization capabilities, thereby contributing to the prevention and treatment of bacterial infections through bandgap engineering of implants and NIR irradiation.

Colony-Based Electrochemistry Reveals Electron Conduction Mechanisms Mediated by Cytochromes and Flavins in Shewanella oneidensis

Bacteria utilize electron conduction in their communities to drive their metabolism, which has led to the development of various environmental technologies, such as electrochemical microbial systems and anaerobic digestion. It is challenging to measure the conductivity among bacterial cells when they hardly form stable biofilms on electrodes. This makes it difficult to identify the biomolecules involved in electron conduction. In the present study, we aimed to identify c-type cytochromes involved in electron conduction in Shewanella oneidensis MR-1 and examine the molecular mechanisms. We established a colony-based bioelectronic system that quantifies bacterial electrical conductivity, without the need for biofilm formation on electrodes. This system enabled the quantification of the conductivity of gene deletion mutants that scarcely form biofilms on electrodes, demonstrating that c-type cytochromes, MtrC and OmcA, are involved in electron conduction. Furthermore, the use of colonies of gene deletion mutants demonstrated that flavins participate in electron conduction by binding to OmcA, providing insight into the electron conduction pathways at the molecular level. Furthermore, phenazine-based electron transfer in Pseudomonas aeruginosa PAO1 and flavin-based electron transfer in Bacillus subtilis 3610 were confirmed, indicating that this colony-based system can be used for various bacteria, including weak electricigens.

A Rapidly Responsive Sensor for Wireless Detection of Early and Mature Microbial Biofilms

Biofilm-associated infections, which are able to resist antibiotics, pose a significant challenge in clinical treatments. Such infections have been linked to various medical conditions, including chronic wounds and implant-associated infections, making them a major public-health concern. Early-detection of biofilm formation offers significant advantages in mitigating adverse effects caused by biofilms. In this work, we aim to explore the feasibility of employing a novel wireless sensor for tracking both early-stage and matured-biofilms formed by the medically relevant bacteria Staphylococcus aureus and Pseudomonas aeruginosa. The sensor utilizes electrochemical reduction of an AgCl layer bridging two silver legs made by inkjet-printing, forming a part of near-field-communication tag antenna. The antenna is interfaced with a carbon cloth designed to promote the growth of microorganisms, thereby serving as an electron source for reduction of the resistive AgCl into a highly-conductive Ag bridge. The AgCl-Ag transformation significantly alters the impedance of the antenna, facilitating wireless identification of an endpoint caused by microbial growth. To the best of our knowledge, this study for the first time presents the evidence showcasing that electrons released through the actions of bacteria can be harnessed to convert AgCl to Ag, thus enabling the wireless, battery-less, and chip-less early-detection of biofilm formation.