Biology subjects

Stubbendieck, R. M.

Publications and source records attributed to Stubbendieck, R. M..

3 recordsLinked to original sources

bioRxiv2026

Siderophore-Mediated Competition Between Cystic Fibrosis Pathogens Increases Virulence Factor Production

The airways of people with cystic fibrosis (CF) are colonized by a polymicrobial community and coinfections with multiple pathogens may exacerbate disease. By analyzing 16S rRNA gene sequencing datasets, we determined that Achromobacter-Pseudomonas coinfection was associated with worse lung function than infection with either pathogen alone, or coinfections with Pseudomonas and other CF bacterial pathogens. We discovered Achromobacter spp. induced production of the siderophore pyoverdine by Pseudomonas aeruginosa strain PAO1 and other clinical isolates on synthetic CF sputum medium (SCFM), supplemented with physiologically relevant iron concentrations. We then tested 21 Achromobacter strains, encompassing seven species, and determined that 17 (81%) induced pyoverdine production. We sequenced the full genomes of these Achromobacter and found 18 (86%) encoded a biosynthetic gene cluster for the production of alcaligin. This compound is an iron-chelating siderophore that has previously been shown to be involved in colonization of the respiratory tract by Bordetella spp. Using mass spectrometry imaging, we confirmed that Achromobacter dolens strain RMS0405 produces alcaligin during coculture with PAO1. Further, we found that supplementing SCFM with increasing iron abolishes pyoverdine induction by PAO1 during coculture. Pyoverdine is known to contribute directly to virulence and regulate expression of other virulence factors. Using transcriptomics and proteomics, we determined that RMS0405 induces a low-iron stress response in PAO1 and stimulates the production of exotoxin A and other known virulence factors. Together, our results indicate that Achromobacter spp. and P. aeruginosa may exacerbate virulence in the airways of people with CF as a byproduct of competition for iron.

microbiology↗

bioRxiv2026

Differential Metabolite Production Underlies Disruption of the Cystic Fibrosis Airway Microbiota by Pathogens

Cystic fibrosis (CF) is a multisystem disease characterized by the accumulation of mucus in the airways that promotes pathogen colonization, leading to respiratory exacerbations, lung failure, and death. Culture-independent approaches have revealed that the CF airway harbors a complex microbiota, including opportunistic pathogens and bacteria that colonize the oropharynx. Here, we reanalyzed 5,260 16S rRNA gene microbiota datasets to infer ecological associations between members of the CF microbiota. We determined that pathogens are more likely to proliferate and dominate when present, while oropharyngeal bacteria are more likely to form persistent communities. Further, we found higher diversity and increasing numbers of inferred interactions were positively associated with lung function. In contrast, pathogens were negatively associated both with each other and with oropharyngeal bacteria, suggesting that they may disrupt the microbiota. To validate these predictions, we cultured 1,597 bacterial isolates from 96 people with CF and performed 12,542 coculture assays against eight representative CF pathogenic and oropharyngeal bacteria. 23% of these interactions resulted in growth inhibition. While Pseudomonas isolates were, on average, the most inhibitory, we observed variable activity among isolates. We then confirmed that Pseudomonas aeruginosa isolates, even those from the same donor and timepoint, exhibited significant differences in their metabolome and bioactivity profiles that correlated with acquisition of mutations. Together, our results suggest that pathogens may disrupt the CF microbiota and bloom in part through differential metabolite production. Furthermore, these data highlight that characterizing multiple isolates is necessary to capture the full landscape of chemically mediated interactions within microbial communities. ImportanceThe cystic fibrosis (CF) airway harbors a complex microbiota, including oropharyngeal bacteria and opportunistic pathogens that establish chronic infections and cause lung failure. We confirmed that microbiota diversity is correlated with health and that a pathogen-dominated microbiota is associated with reduced lung function. We then inferred microbial interactions, which suggested that pathogens are able to disrupt the microbiota. To validate these predictions, we cultured bacterial isolates from people with CF and performed thousands of coculture assays, finding that approximately one-quarter of interactions resulted in growth inhibition. Pseudomonas broadly inhibited other members of the CF airway microbiota. However, we observed marked variability in bioactivity and metabolite profiles of Pseudomonas aeruginosa isolates, even from the same donor at the same time. Our results suggest that pathogens disrupt the CF microbiota, possibly through bioactive metabolite production, and that characterizing multiple isolates is necessary to capture the complete picture of interactions in these communities.

microbiology↗

bioRxiv2018

Bacterial competition mediated by siderophore production among the human nasal microbiota

Resources available in the human nasal cavity are limited. Therefore, to successfully colonize the nasal cavity, bacteria must compete for scarce nutrients. Competition may occur directly through interference (e.g., antibiotics) or indirectly by nutrient sequestration. To investigate the nature of nasal bacterial competition, we performed co-culture inhibition assays between nasal Actinobacteria and Staphylococcus spp. We found that Staphylococcus epidermidis isolates were sensitive to growth inhibition by Actinobacteria but Staphylococcus aureus isolates were resistant to inhibition. Among Actinobacteria, we observed that Corynebacterium spp. were variable in their ability to inhibit S. epidermidis. We sequenced the genomes of ten Corynebacterium spp. isolates, including three Corynebacterium propinquum that strongly inhibited S. epidermidis and seven other Corynebacterium spp. isolates that only weakly inhibited S. epidermidis. Using a comparative genomics approach, we found that the C. propinquum genomes were enriched in genes for iron acquisition and encoded a biosynthetic gene cluster (BGC) for siderophore production, absent in the non-inhibitory Corynebacterium spp. genomes. Using a chromeazurol S assay, we confirmed that C. propinquum produced siderophores. We demonstrated that iron supplementation rescued S. epidermidis from inhibition by C. propinquum, suggesting that inhibition was due to iron restriction through siderophore production. Using comparative metabolomics, we identified the siderophore produced by C. propinquum as dehydroxynocardamine. Finally, we confirmed that the dehydroxynocardamine BGC is expressed in vivo by analyzing human nasal metatranscriptomes from the NIH Human Microbiome Project.\n\nTogether, our results suggest that bacteria produce siderophores to compete for limited available iron in the nasal cavity and improve their fitness.\n\nIMPORTANCEWithin the nasal cavity, interference competition through antimicrobial production is prevalent. For instance, nasal Staphylococcus spp. strains can inhibit the growth of other bacteria through the production of nonribosomal peptides and ribosomally synthesized and post-translationally modified peptides. In contrast, bacteria engaging in exploitation competition modify the external environment to prevent competitors from growing, usually by depleting access to essential nutrients. As the nasal cavity is a nutrient limited environment, we hypothesized that exploitation competition occurs in this system. We determined that Corynebacterium propinquum produces an iron-chelating siderophore and is able to use this molecule to sequester iron and inhibit the growth of Staphylococcus epidermidis. Further, we found that the genes required for siderophore production are expressed in vivo. Thus, though siderophore production by bacteria is often considered a virulence trait, our work indicates that bacteria may produce siderophores to compete for limited iron in the human nasal cavity.

microbiology↗