Biology subjects

Vollenweider, V.

Publications and source records attributed to Vollenweider, V..

3 recordsLinked to original sources

bioRxiv2026

Siderophore-mediated inhibition of Legionella pneumophila by environmental Pseudomonas isolates

The genus Legionella comprises opportunistic pathogenic bacteria commonly found in natural and engineered water systems, where they interact with environmental microbes and protozoa, primarily in biofilms. Legionella pneumophila is the main causative agent of Legionnaires disease and is transmitted through inhalation of contaminated aerosols. Iron availability is a critical factor for L. pneumophila growth, persistence, and virulence, yet iron is often limited in aquatic environments. To overcome iron scarcity, many bacteria produce siderophores, secondary metabolites that scavenge ferric iron. Because siderophores are chemically diverse and species specific, they play a key role in inter-species competition and can withhold iron from competitors. Here, we investigated the effects of iron depletion and siderophore-mediated competition on L. pneumophila using commercial pyoverdines and extracellular metabolites from environmental Pseudomonas strains. Growth assays showed that L. pneumophila can grow under iron-limited conditions but with lag phases extended by more than 20 hours. Pyoverdines inhibited growth in a concentration-dependent manner, primarily increasing the time to mid-log phase (t_mid). Supernatants and crude pyoverdine extracts from siderophore-producing Pseudomonas strains caused the strongest inhibition, including lag-phase extensions of up to 55 hours or complete growth arrest. These results demonstrate that siderophore-producing bacteria can suppress L. pneumophila by limiting iron availability.

microbiology↗

bioRxiv2024

Pyoverdine-antibiotic combination treatment: its efficacy and effects on resistance evolution in Escherichia coli

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 promising approach to induce growth arrest in pathogens through iron starvation. While we have 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 investigate the propensity of different Escherichia coli variants to evolve resistance against pyoverdine, the cephalosporin antibiotic ceftazidime, and their combination. We found that strong resistance against ceftazidime and weak resistance against pyoverdine evolved in the wildtype E. coli strain under single and combination 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, resistance phenotypes were attenuated under combination treatment, particularly in an E. coli strain carrying a costly multicopy plasmid. Altogether, our results show that pyoverdine as an antibacterial is particularly potent and evolutionarily robust against plasmid-carrying E. coli strains, presumably because iron starvation compromises both cellular metabolism and plasmid replication.

microbiology↗

bioRxiv2023

Antimicrobial activity of iron-depriving pyoverdines against human opportunistic pathogens

The global rise of antibiotic resistance calls for new drugs against bacterial pathogens. A common approach is to search for natural compounds deployed by microbes to inhibit competitors. Here we show that the iron chelating pyoverdines, siderophores produced by environmental Pseudomonas spp., have strong antibacterial properties by inducing iron starvation and growth arrest in pathogens. A screen of 320 natural Pseudomonas isolates used against 12 human pathogens uncovered several pyoverdines with particularly high antibacterial properties and distinct chemical characteristics. The most potent pyoverdine effectively reduced growth of the pathogens Acinetobacter baumannii, Klebsiella pneumoniae and Staphylococcus aureus in a concentration- and iron-dependent manner. Pyoverdine increased survival of infected Galleria mellonella host larvae, and showed low toxicity for the host, mammalian cell lines, and erythrocytes. Furthermore, experimental evolution combined with whole-genome sequencing revealed reduced potentials for resistance evolution compared to an antibiotic. Thus, pyoverdines from environmental strains have the potential to become a new class of sustainable antibacterials against specific human pathogens.

microbiology↗