Inhibition of Respiration of Candida albicans by Small Molecules Increases Phagocytosis Efficacy by Macrophages

Resilience in Resistance: The Role of Cell Wall Integrity in Multidrug-Resistant Candida

The Candida species cell wall plays a pivotal role as a structural and functional barrier against external aggressors and as an intermediary in host-pathogen interactions. Candida species exhibit unique adaptations in their cell wall composition, with varying proportions of chitin, mannans, and β-glucans influenced by the environmental conditions and the morphological states. These components not only maintain cellular viability under osmotic, thermal, and chemical stress, but also serve as the key targets for novel antifungal strategies. MAPK signaling pathways, like the cell wall integrity pathway and the high-osmolarity glycerol pathway, play a crucial role in responding to cell wall stressors. Due to the rise of antifungal resistance and its clinical challenges, there is a need to identify new antifungal targets. This review discusses the recent advances in understanding the mechanisms underlying cell wall integrity, their impact on antifungal resistance and virulence, and their potential as therapeutic targets of C. albicans, N. glabratus, and C. auris.

Mitochondrial Reactive Oxygen Species in Infection and Immunity

Reactive oxygen species (ROS) contain at least one oxygen atom and one or more unpaired electrons and include singlet oxygen, superoxide anion radical, hydroxyl radical, hydroperoxyl radical, and free nitrogen radicals. Intracellular ROS can be formed as a consequence of several factors, including ultra-violet (UV) radiation, electron leakage during aerobic respiration, inflammatory responses mediated by macrophages, and other external stimuli or stress. The enhanced production of ROS is termed oxidative stress and this leads to cellular damage, such as protein carbonylation, lipid peroxidation, deoxyribonucleic acid (DNA) damage, and base modifications. This damage may manifest in various pathological states, including ageing, cancer, neurological diseases, and metabolic disorders like diabetes. On the other hand, the optimum levels of ROS have been implicated in the regulation of many important physiological processes. For example, the ROS generated in the mitochondria (mitochondrial ROS or mt-ROS), as a byproduct of the electron transport chain (ETC), participate in a plethora of physiological functions, which include ageing, cell growth, cell proliferation, and immune response and regulation. In this current review, we will focus on the mechanisms by which mt-ROS regulate different pathways of host immune responses in the context of infection by bacteria, protozoan parasites, viruses, and fungi. We will also discuss how these pathogens, in turn, modulate mt-ROS to evade host immunity. We will conclude by briefly giving an overview of the potential therapeutic approaches involving mt-ROS in infectious diseases.

Systematic identification and characterization of five transcription factors mediating the oxidative stress response in Candida albicans

Candida albicans is an opportunistic human fungal pathogen that causes superficial and systemic infections, particularly in immunocompromised individuals. In response to C. albicans infection, innate immune cells of the host produce and accumulate reactive oxygen species (ROS), which can lead to irreversible damage and apoptosis of fungal cells. Several transcription factors involved in this oxidative stress response have been identified; however, a systematic study to identify the transcription factors that mediate the oxidative stress response has not yet been conducted. Here, we screened a comprehensive transcription factor mutant library consisting of 211 transcription factor deletion mutant strains in the presence and absence of hydrogen peroxide (H2O2), a potent ROS inducer, and identified five transcription factors (Skn7, Dpb4, Cap1, Dal81, and Stp2) that are sensitive to H2O2. Genome-wide transcriptional profiling revealed that H2O2 induces a discrete set of differentially regulated genes among the five identified transcription factor mutant strains. Functional enrichment analysis identified KEGG pathways pertaining to glycolysis/gluconeogenesis, amino sugar and nucleotide sugar metabolism, and ribosome synthesis as the most enriched pathways. GO term analysis of the top common differentially expressed genes among the transcription factor mutant strains identified hexose catabolism and iron transport as the most enriched GO terms upon exposure to H2O2. This study is the first to systematically identify and characterise the transcription factors involved in the response to H2O2. Based on our transcriptional profiling results, we found that exposure to H2O2 modulates several downstream genes involved in fungal virulence. Overall, this study sheds new light on the metabolism, physiological functions, and cellular processes involved in the H2O2-induced oxidative stress response in C. albicans.

Label-free microfluidic device reveals single cell phagocytic activity and screens plant medicine rapidly

Phagocytic activity is an extremely important indicator that evaluates medicinal effects related to the immune system and functions to investigate the mechanism of how a drug works under conditions such as immunological regulation, immune tolerance, inflammation, cancer, etc. Current techniques based on flow cytometry, fluorescence imaging or numbering CFUs after cell lysis for detecting phagocytosis suffer from long terms of bacteria culturing and complex preparation steps for fluorescent labeling or require a large amount of cell samples to be tested. This study aims at developing a simple and fast method for testing the phagocytic activity of unlabeled and native cells, taking advantage of very high-resolution direct current insulator-based dielectrophoresis (DC-iDEP). The properties of cells are characterized by native whole cell biophysical properties. This strategy not only eliminates the time-consuming bacterial culture work after cell lysis, but also lowers the expenses of bacteria labeling. The introduction of microfluidics reduces the sample volume or reagent needed. The analysis of the biophysical property distributions of native cells and medicine treated cells may lead to a less expensive and rapid tool for evaluating medicinal effects. Furthermore, berberine was investigated for decreasing the phagocytic activity of macrophages and used for comparison of activities. This study works on establishing a label-free, unbiased, and non-destructive method to determine cell phagocytic activity and investigate its use in evaluating medicinal effects on phagocytosis in a single step within a short time.

Microbial Sensing and Removal of Heavy Metals: Bioelectrochemical Detection and Removal of Chromium(VI) and Cadmium(II)

The presence of inorganic pollutants such as Cadmium(II) and Chromium(VI) could destroy our environment and ecosystem. To overcome this problem, much attention was directed to microbial technology, whereas some microorganisms could resist the toxic effects and decrease pollutants concentration while the microbial viability is sustained. Therefore, we built up a complementary strategy to study the biofilm formation of isolated strains under the stress of heavy metals. As target resistive organisms, Rhizobium-MAP7 and Rhodotorula ALT72 were identified. However, Pontoea agglumerans strains were exploited as the susceptible organism to the heavy metal exposure. Among the methods of sensing and analysis, bioelectrochemical measurements showed the most effective tools to study the susceptibility and resistivity to the heavy metals. The tested Rhizobium strain showed higher ability of removal of heavy metals and more resistive to metals ions since its cell viability was not strongly inhibited by the toxic metal ions over various concentrations. On the other hand, electrochemically active biofilm exhibited higher bioelectrochemical signals in presence of heavy metals ions. So by using the two strains, especially Rhizobium-MAP7, the detection and removal of heavy metals Cr(VI) and Cd(II) is highly supported and recommended.

Microbial Electrochemical Systems: Principles, Construction and Biosensing Applications

Microbial electrochemical systems are a fast emerging technology that use microorganisms to harvest the chemical energy from bioorganic materials to produce electrical power. Due to their flexibility and the wide variety of materials that can be used as a source, these devices show promise for applications in many fields including energy, environment and sensing. Microbial electrochemical systems rely on the integration of microbial cells, bioelectrochemistry, material science and electrochemical technologies to achieve effective conversion of the chemical energy stored in organic materials into electrical power. Therefore, the interaction between microorganisms and electrodes and their operation at physiological important potentials are critical for their development. This article provides an overview of the principles and applications of microbial electrochemical systems, their development status and potential for implementation in the biosensing field. It also provides a discussion of the recent developments in the selection of electrode materials to improve electron transfer using nanomaterials along with challenges for achieving practical implementation, and examples of applications in the biosensing field.