Exploring the antibacterial action of gliotoxin: Does it induce oxidative stress or protein damage?

The study aimed to investigate the effects of gliotoxin (GTX), a secondary fungal metabolite belonging to the epipolythiodioxopiperazines class, on Gram-positive and Gram-negative bacteria. While the cytotoxic mechanism of GTX on eukaryotes is well understood, its interaction with bacteria is not yet fully comprehended. The study discovered that S. epidermidis displayed a higher uptake rate of GTX than E.coli. However, Gram-negative bacteria required higher doses of GTX than Gram-positive bacteria to experience the bactericidal effect, which occurred within 4 h for both types of bacteria. The treatment of bioluminescent sensor E.coli MG1655 pKatG-lux with GTX resulted in oxidative stress. Pre-incubation with the antioxidant Trolox did not increase the GTX inhibitory dose, however, slightly increased the bacterial growth rate comparing to GTX alone. At the same time, we found that GTX inhibitory dose was significantly increased by the pretreatment of bacteria with 2-mercaptoethanol and reduced glutathione. Using another biosensor, E. coli MG1655 pIpbA-lux, we showed that bacteria treated with GTX exhibited heat shock stress. SDS-page electrophoresis demonstrated protein aggregation under the GTX treatment. In addition, we have found that gliotoxin's action on bacteria was significantly inhibited when zinc salt was added to the growth medium.

Fungal Endophytes of Vitis vinifera-Plant Growth Promoters or Potentially Toxinogenic Agents?

Fungal endophytes occurring in grapevine (Vitis vinifera L.) are usually important sources of various compounds with biological activities with great potential for use in agriculture. Nevertheless, many species isolated from this plant belong to the genera Fusarium, Alternaria, or Aspergillus, all of which are well-known to produce mycotoxins. Our study is focused on the assessment of the toxinogenic potential of fungal endophytes isolated from vineyards in the Czech Republic. In total, 20 endophytic fungal species were cultivated in wine must, and 57 mycotoxins of different classes were analysed by liquid chromatography coupled with mass spectrometry. As a result, alternariol, tentoxin, meleagrin, roquefortine C, gliotoxin, and verruculogen were detected in the culture medium, of which verruculogen followed by gliotoxin were the most frequent (present in 90 and 40% of samples, respectively) and most concentrated (up to thousands ng/mL). The alternaria mycotoxins alternariol and tentoxin were detected not only in Alternaria sp. cultures, but traces of these mycotoxins were also quantified in the Diatripe and Epicoccum cultures. Meleagrin and roquefortine C were detected in Didymella sancta and Penicillium crustosum, gliotoxin was detected in Alternaria sp., Didymella sp., Aureobasidium pullulans, Cladosporium herbarum, Penicillium crustosum and Pleurophoma ossicola, and verruculogen was quantified in 99% of endophytic isolates investigated. The potential of endophytes to produce mycotoxins should be carefully checked, specifically in cases where they are intended for the purpose of V. vinifera growing.

Cytotoxicity of Aspergillus Section Fumigati Isolated from Health Care Environments

This study analyzed 57 Aspergillus section Fumigati (AF) isolates collected by active and passive sampling (N = 450) in several health care facilities and from biological sampling of health care workers (N = 25) and controls (N = 22) in Portugal. All isolates were cultured in different media and screened for azole resistance. Cytotoxicity was assessed for 40 isolates in lung epithelial cells and kidney cells using the MTT assay. Aspergillus section Fumigati was prevalent in the health care facilities and in nasal swabs from health care workers and controls. All AF isolates reduced cell viability and presented medium to high cytotoxicity, with cytotoxicity being significantly higher in A549 lung epithelial cells. The cytotoxicity of isolates from air and nasal swab samples suggested the inhalation route as a risk factor. Notably, 42% of AF isolates exhibited a pattern of reduced susceptibility to some of the most used antifungals available for the treatment of patients infected with these fungi. In sum, the epidemiology and clinical relevance of Aspergillus section Fumigati should continue to be addressed. A deeper understanding of the mechanisms underlying Aspergillus-mediated cytotoxicity is necessary.

Host and Pathogen Communication in the Respiratory Tract: Mechanisms and Models of a Complex Signaling Microenvironment

Chronic lung diseases are a leading cause of morbidity and mortality across the globe, encompassing a diverse range of conditions from infections with pathogenic microorganisms to underlying genetic disorders. The respiratory tract represents an active interface with the external environment having the primary immune function of resisting pathogen intrusion and maintaining homeostasis in response to the myriad of stimuli encountered within its microenvironment. To perform these vital functions and prevent lung disorders, a chemical and biological cross-talk occurs in the complex milieu of the lung that mediates and regulates the numerous cellular processes contributing to lung health. In this review, we will focus on the role of cross-talk in chronic lung infections, and discuss how different cell types and signaling pathways contribute to the chronicity of infection(s) and prevent effective immune clearance of pathogens. In the lung microenvironment, pathogens have developed the capacity to evade mucosal immunity using different mechanisms or virulence factors, leading to colonization and infection of the host; such mechanisms include the release of soluble and volatile factors, as well as contact dependent (juxtracrine) interactions. We explore the diverse modes of communication between the host and pathogen in the lung tissue milieu in the context of chronic lung infections. Lastly, we review current methods and approaches used to model and study these host-pathogen interactions in vitro, and the role of these technological platforms in advancing our knowledge about chronic lung diseases.