microLife最新文献

The French Phage Network organizes a scientific meeting every year in which the community of researchers from academia and industry, as well as clinicians participate due to the growing interest in phage therapy. Although centered on giving exposure to future generations of scientists from the French community with senior investigators invited as main speakers, the meeting has also welcomed participants from other countries. Covering almost every aspect of bacteriophage biology, the meeting is an opportunity not only to expose the youngest to a broad range of topics, but also to share their most recent "work in progress" without undergoing a stringent selection process to obtain an oral presentation slot. This report reflects the dynamism of the research field on bacteriophages across multiple disciplines, including molecular and structural biology, ecology, evolution, therapy, and biotechnology.

[This corrects the article DOI: 10.1093/femsml/uqae019.].

Oil reservoirs are society's primary source of hydrocarbons. While microbial communities in industrially exploited oil reservoirs have been investigated in the past, pristine microbial communities in untapped oil reservoirs are little explored, as are distribution patterns of respective genetic signatures. Here, we show that a pristine oil sample contains a complex community consisting of bacteria and fungi for the degradation of hydrocarbons. We identified microorganisms and their pathways for the degradation of methane, n-alkanes, mono-aromatic, and polycyclic aromatic compounds in a metagenome retrieved from biodegraded petroleum encountered in a subsurface reservoir in the Barents Sea. Capitalizing on marker genes from metagenomes and public data mining, we compared the prokaryotes, putative viruses, and putative plasmids of the sampled site to those from 10 other hydrocarbon-associated sites, revealing a shared network of species and genetic elements across the globe. To test for the potential dispersal of the microbes and predicted elements via seawater, we compared our findings to the Tara Ocean dataset, resulting in a broad distribution of prokaryotic and viral signatures. Although frequently shared between hydrocarbon-associated sites, putative plasmids, however, showed little coverage in the Tara Oceans dataset, suggesting an undiscovered mode of transfer between hydrocarbon-affected ecosystems. Based on our analyses, genetic information is globally shared between oil reservoirs and hydrocarbon-associated sites, and we propose that currents and other physical occurrences within the ocean along with deep aquifers are major distributors of prokaryotes and viruses into these subsurface ecosystems.

Bacterial small proteins impact diverse physiological processes, however, technical challenges posed by small size hampered their systematic identification and biochemical characterization. In our quest to uncover small proteins relevant for Salmonella pathogenicity, we previously identified YjiS, a 54 amino acid protein, which is strongly induced during this pathogen's intracellular infection stage. Here, we set out to further characterize the role of YjiS. Cell culture infection assays with Salmonella mutants lacking or overexpressing YjiS suggested this small protein to delay bacterial escape from macrophages. Mutant scanning of the protein's conserved, arginine-rich DUF1127 domain excluded a major effect of single amino acid substitutions on the infection phenotype. A comparative dual RNA-seq assay uncovered the molecular footprint of YjiS in the macrophage response to infection, with host effects related to oxidative stress and the cell cortex. Bacterial cell fractionation experiments demonstrated YjiS to associate with the inner membrane and proteins interacting with YjiS in pull-down experiments were enriched for inner membrane processes. Among the YjiS interactors was the two-component system SsrA/B, the master transcriptional activator of intracellular virulence genes and a suppressor of flagellar genes. Indeed, in the absence of YjiS, we observed elevated expression of motility genes and an increased number of flagella per bacterium. Together, our study points to a role for Salmonella YjiS as a membrane-associated timer of pathogen dissemination.

Although not essential for their growth, the production of secondary metabolites increases the fitness of the producing microorganisms in their natural habitat by enhancing establishment, competition, and nutrient acquisition. The Gram-positive soil-dwelling bacterium, Bacillus subtilis, produces a variety of secondary metabolites. Here, we investigated the regulatory relationship between the non-ribosomal peptide surfactin and the sactipeptide bacteriocin subtilosin A. We discovered that B. subtilis mutants lacking surfactin production exhibited higher production of subtilosin A compared to their parental wild-type strain. Additionally, spatial visualization of B. subtilis production of metabolites demonstrated that surfactin secreted by a wild-type colony could suppress subtilosin A production in an adjacent mutant colony lacking surfactin production. Reporter assays were performed using mutants in specific transcriptional regulators, which confirmed the role of ResD as an activator of the subtilosin A encoding biosynthetic gene cluster (BGC), while the removal of Rok and AbrB repressors increased the expression of the BGC, which was further enhanced by additional deletion of surfactin, suggesting that a so-far-unidentified regulator might mediate the influence of surfactin on production of subtilosin A. Our study reveals a regulatory influence of one secondary metabolite on another, highlighting that the function of secondary metabolites could be more complex than its influence on other organisms and interactions among secondary metabolites could also contribute to their ecological significance.

Evolutionary processes acting on populations of organized molecules preceded the origin of living organisms. These prebiotic entities were independently and repeatedly produced [i.e. (re)-produced] by the assembly of their components, following an iterative process giving rise to nearly but not fully identical replicas, allowing for a prebiotic form of Darwinian evolution. Natural selection favored the more persistent assemblies, some possibly modifying their own internal structure, or even their environment, thereby acquiring function. We refer to these assemblies as proto-organs. In association with other assemblies (e.g. in a coacervate or encapsulated within a vesicle), such proto-organs could evolve and acquire a role within the collective when their coexistence favored the selection of the ensemble. Along millions of years, an extraordinarily small number of successful combinations of those proto-organs co-occurring in spatially individualizing compartments might have co-evolved forming a proto-metabolic and proto-genetic informative network, eventually leading to the selfreplication of a very few. Thus, interactions between encapsulated proto-organs would have had a much higher probability of evolving into proto-organisms than interactions among simpler molecules. Multimolecular forms evolve functions; thus, functional organs would have preceded organisms.

The polyene antimycotic amphotericin B (AmB) and its liposomal formulation AmBisome belong to the treatment options of invasive aspergillosis caused by Aspergillus fumigatus. Increasing resistance to AmB in clinical isolates of Aspergillus species is a growing concern, but mechanisms of AmB resistance remain unclear. In this study, we conducted a proteomic analysis of A. fumigatus exposed to sublethal concentrations of AmB and AmBisome. Both antifungals induced significantly increased levels of proteins involved in aromatic acid metabolism, transmembrane transport, and secondary metabolite biosynthesis. One of the most upregulated proteins was RtaA, a member of the RTA-like protein family, which includes conserved fungal membrane proteins with putative functions as transporters or translocases. Accordingly, we found that RtaA is mainly located in the cytoplasmic membrane and to a minor extent in vacuolar-like structures. Deletion of rtaA led to increased polyene sensitivity and its overexpression resulted in modest resistance. Interestingly, rtaA expression was only induced by exposure to the polyenes AmB and nystatin, but not by itraconazole and caspofungin. Orthologues of rtaA were also induced by AmB exposure in A. lentulus and A. terreus. Deletion of rtaA did not significantly change the ergosterol content of A. fumigatus, but decreased fluorescence intensity of the sterol-binding stain filipin. This suggests that RtaA is involved in sterol and lipid trafficking, possibly by transporting the target ergosterol to or from lipid droplets. These findings reveal the contribution of RtaA to polyene resistance in A. fumigatus, and thus provide a new putative target for antifungal drug development.

Microbial natural products-low molecular weight compounds biosynthesized by microorganisms-form the foundation of important modern therapeutics, including antibiotics, immunomodulators, and anti-cancer agents. This perspective discusses and contrasts two emerging approaches for uncovering natural products of the past. On the one hand, ancestral sequence reconstruction allows recreating biosynthetic pathways that date back hundreds of millions of years. On the other hand, sequencing and de novo assembly of ancient DNA reveals the biosynthetic potential of ancient microbial communities up to 100 000 years. Together, these approaches unveil an otherwise hidden reservoir of functional and structural molecular diversity. They also offer new opportunities to study the biological function and evolution of these molecules within an archaeological context.

Extracellular vesicles (EVs) have gained attention as facilitators of intercellular as well as interkingdom communication during host-microbe interactions. Recently we showed that upon infection, host polymorphonuclear leukocytes produce antifungal EVs targeting the clinically important fungal pathogen Aspergillus fumigatus; however, the small size of EVs (<1 µm) complicates their functional analysis. Here, we employed a more tractable, reporter-based system to label host alveolar epithelial cell-derived EVs and enable their visualization during in vitro A. fumigatus interaction. Fusion of EV marker proteins (CD63, CD9, and CD81) with a Nanoluciferase (NLuc) and a green fluorescent protein (GFP) facilitated their relative quantification by luminescence and visualization by a fluorescence signal. The use of an NLuc fused with a GFP is advantageous as it allows for quantification and visualization of EVs simultaneously without additional external manipulation and to distinguish subpopulations of EVs. Using this system, visualization and tracking of EVs was possible using confocal laser scanning microscopy and advanced imaging analysis. These experiments revealed the propensity of host cell-derived EVs to associate with the fungal cell wall and ultimately colocalize with the cell membrane of A. fumigatus hyphae in large numbers. In conclusion, we have created a series of tools to better define the complex interplay of host-derived EVs with microbial pathogens.

Antibiotic resistance is a growing concern for global health, demanding innovative and effective strategies to combat pathogenic bacteria. Pyoverdines, iron-chelating siderophores produced by environmental Pseudomonas spp., present a novel class of promising compounds to induce growth arrest in pathogens through iron starvation. While we previously demonstrated the efficacy of pyoverdines as antibacterials, our understanding of how these molecules interact with antibiotics and impact resistance evolution remains unknown. Here, we investigated the propensity of three Escherichia coli strains to evolve resistance against pyoverdine, the cephalosporin antibiotic ceftazidime, and their combination. We used a naive E. coli wildtype strain and two isogenic variants carrying the bla _TEM-1 β-lactamase gene on either the chromosome or a costly multicopy plasmid to explore the influence of genetic background on selection for resistance. We found that strong resistance against ceftazidime and weak resistance against pyoverdine evolved in all E. coli variants under single treatment. Ceftazidime resistance was linked to mutations in outer membrane porin genes (envZ and ompF), whereas pyoverdine resistance was associated with mutations in the oligopeptide permease (opp) operon. In contrast, ceftazidime resistance phenotypes were attenuated under combination treatment, especially for the E. coli variant carrying bla _TEM-1 on the multicopy plasmid. Altogether, our results show that ceftazidime and pyoverdine interact neutrally and that pyoverdine as an antibacterial is particularly potent against plasmid-carrying E. coli strains, presumably because iron starvation compromises both cellular metabolism and plasmid replication.