Biology subjects

Katharios-Lanwermeyer, S.

Publications and source records attributed to Katharios-Lanwermeyer, S..

5 recordsLinked to original sources

bioRxiv2025

Stenotrophomonas maltophilia exhibits defensive multicellularity in response to a Pseudomonas aeruginosa quorum sensing molecule

Microorganisms commonly exist in polymicrobial communities, where they can respond to interspecies secreted molecules by altering behaviors and physiology, however, the underlying mechanisms remain underexplored. Here we investigated interactions between Stenotrophomonas maltophilia and Pseudomonas aeruginosa, co-infecting opportunistic pathogens found in pneumonia and chronic lung infections, including in cystic fibrosis. We found that S. maltophilia forms robust protective multicellular aggregates upon exposure to P. aeruginosa secreted factors. Experimental evolution for lack of aggregation selected for fimbrial mutations and we found that fimbriae are required on both interacting S. maltophilia cells for aggregation. Untargeted metabolomics and targeted validations revealed that the quorum sensing molecule Pseudomonas quinolone signal (PQS) directly induced S. maltophilia aggregation, and co-localized with the aggregates. Further, in co-culture with P. aeruginosa, wild-type S. maltophilia formed aggregates, resulting in up to 75-fold increased survival from P. aeruginosa competition compared to fimbrial mutants. Finally, multiple other bacterial species similarly aggregated upon exposure to P. aeruginosa exoproducts, indicating a more general response. Collectively, our work identifies a novel multispecies interaction where a quorum sensing molecule from a co-infecting pathogen is sensed as a danger signal, thereby inducing a protective multicellular response.

microbiology↗

bioRxiv2021

The Diguanylate Cyclase YfiN of Pseudomonas aeruginosa Regulates Biofilm Maintenance in Response to Peroxide

Pseudomonas aeruginosa forms surface-attached communities that persist in the face of antimicrobial agents and environmental perturbation. Published work has found extracellular polysaccharide (EPS) production, regulation of motility and induction of stress response pathways as contributing to biofilm tolerance during such insults. However, little is known regarding the mechanism(s) whereby biofilm maintenance is regulated when exposed to such environmental challenges. Here, we provide evidence that the diguanylate cyclase YfiN is important for the regulation of biofilm maintenance when exposed to peroxide. We find that, compared to the wild type (WT), static biofilms of the {Delta}yfiN mutant exhibit a maintenance defect, which can be further exacerbated by exposure to peroxide (H2O2); this defect can be rescued through genetic complementation. Additionally, we found that the {Delta}yfiN mutant biofilms produce less c-di-GMP than WT, and that H2O2 treatment enhanced motility of surface-associated bacteria and increased cell death for the {Delta}yfiN mutant grown as a biofilm compared to WT biofilms. These data provide evidence that YfiN is required for biofilm maintenance by P. aeruginosa, via c-di-GMP signaling, to limit motility and protect viability in response to peroxide stress. These findings add to the growing recognition that biofilm maintenance by P. aeruginosa is an actively regulated process that is controlled, at least in part, by the wide array of c-di-GMP metabolizing enzymes found in this microbe. ImportanceWe build on previous findings that suggest that P. aeruginosa utilizes c-di-GMP metabolizing enzymes to actively maintain a mature biofilm. Here, we explore how the diguanylate cyclase YfiN contributes to the regulation of biofilm maintenance during peroxide exposure. We find that mature P. aeruginosa biofilms require YfiN to synthesize c-di-GMP, regulate motility and to insure viability during peroxide stress. These findings provide further evidence that the modulation of c-di-GMP in response to environmental signals is an important mechanism by which biofilms are maintained.

microbiology↗

bioRxiv2021

Differential surface competition and biofilm invasion strategies of Pseudomonas aeruginosa PA14 and PA01

Pseudomonas aeruginosa strains PA14 and PAO1 are among the two best characterized model organisms used to study the mechanisms of biofilm formation, while also representing two distinct lineages of P. aeruginosa. Our previous work showed that P. aeruginosa PA14 and PAO1 use distinct strategies to initiate biofilm growth. Using differentially-labeled strains and microfluidic devices, we show that PAO1 can outcompete PA14 in a head-to-head competition during early colonization of a surface, can do so in constant and perturbed environments, that this advantage is specific to biofilm growth and requires production of the Psl polysaccharide. In contrast, the P. aeruginosa PA14 exhibits a competitive fitness advantage when invading a pre-formed biofilm and is better able to tolerate starvation than PAO1 in the biofilm context. These data support the model that while P. aeruginosa PAO1 and PA14 are both able to effectively colonize surfaces, these strains use distinct strategies that are advantageous under different environmental settings. ImportanceRecent studies indicate that P. aeruginosa PAO1 and PA14 use distinct strategies to initiate biofilm formation, with PAO1 committing to the surface through a processive mode of attachment, while PA14 uses a non-processive surface engagement strategy. We investigated whether their respective colonization strategies impact their ability to effectively compete under different biofilm-forming regimes. Our work shows that these different strategies do indeed impact how these strains colonize the surface: PAO1 dominates during colonization of a naive surface, while PA14 is more effective in colonizing a pre-formed biofilm or withstanding starvation conditions. These data suggest that even for very similar microbes there may be distinct strategies to successfully colonize and persist on surfaces during the biofilm life cycle.

microbiology↗

bioRxiv2021

Architecture of cell-cell junctions in situ reveals a mechanism for bacterial biofilm inhibition

Many bacteria, including the major human pathogen Pseudomonas aeruginosa, are naturally found in multicellular, antibiotic-tolerant biofilm communities, where cells are embedded in an extracellular matrix of polymeric molecules. Cell-cell interactions within P. aeruginosa biofilms are mediated by CdrA, a large, membrane-associated adhesin present in the extracellular matrix of biofilms, regulated by the cytoplasmic concentration of cyclic diguanylate. Here, using electron cryotomography of focused-ion beam milled specimens, we report the architecture of CdrA molecules in the extracellular matrix of P. aeruginosa biofilms at intact cell-cell junctions. Combining our in situ observations at cell-cell junctions with biochemistry, native mass spectrometry and cellular imaging, we demonstrate that CdrA forms an extended structure that projects from the outer membrane to tether cells together via polysaccharide binding partners. We go on to show the functional importance of CdrA using custom single-domain antibody (nanobody) binders. Nanobodies targeting the tip of functional cell-surface CdrA molecules could be used to inhibit bacterial biofilm formation or disrupt pre-existing biofilms in conjunction with bactericidal antibiotics. These results reveal a functional mechanism for cell-cell interactions within bacterial biofilms and highlight the promise of using inhibitors targeting biofilm cell-cell junctions to prevent or treat problematic, chronic bacterial infections.

microbiology↗

bioRxiv2020

Pseudomonas aeruginosa uses c-di-GMP phosphodiesterases RmcA and MorA to regulate biofilm maintenance

While the early stages of biofilm formation have been well characterized, less is known about the requirements for Pseudomonas aeruginosa to maintain a mature biofilm. We utilized a P. aeruginosa-phage interaction to find that rmcA and morA, two genes which encode for c-di-GMP-degrading phosphodiesterase (PDEs) enzymes, are important for the regulation of biofilm maintenance. Deletion of these genes initially results in an elevated biofilm phenotype characterized by increased production of c-di-GMP, Pel polysaccharide and biofilm biomass. In contrast to the wild-type strain, these mutants were unable to maintain the biofilm when exposed to carbon-limited conditions. The susceptibility to nutrient limitation, and subsequent loss of biofilm viability of these mutants, was phenotypically reproduced with a stringent response mutant ({Delta}relA {Delta}spoT), indicating that the {Delta}rmcA and {Delta}morA mutants may be unable to appropriately respond to nutrient limitation. Genetic and biochemical data indicate that RmcA and MorA physically interact with the Pel biosynthesis machinery, supporting a model whereby unregulated Pel biosynthesis contributes to the death of the {Delta}rmcA and {Delta}morA mutant strains in an established biofilm when nutrient-limited. These findings provide evidence that c-di-GMP-mediated regulation is required for mature biofilms of P. aeruginosa to effectively respond to changing availability of nutrients. Furthermore, the PDEs involved in biofilm maintenance are distinct from those required for establishing a biofilm, thus indicating that a wide variety of c-di-GMP metabolizing enzymes in organisms like P. aeruginosa likely allows for discrete control over the formation, maintenance or dispersion of biofilms. ImportanceRecent advances in our understanding of c-di-GMP signaling have provided key insights into the regulation of biofilms. Despite an improved understanding of how they initially form, the processes that facilitate the long-term maintenance of these multicellular communities remain opaque. We found that P. aeruginosa requires two phosphodiesterases, RmcA and MorA, to maintain a mature biofilm and that P. aeruginosa biofilms lacking these PDEs succumb to nutrient limitation and die. The biofilm maintenance deficiency observed in {Delta}rmcA and {Delta}morA mutants was also found in the stringent response defective {Delta}relA {Delta}spoT strain, suggesting that a regulatory intersection between c-di-GMP signaling, EPS biosynthesis and the nutrient limitation response is important for persistent surface growth. We uncover components of an important regulatory system needed for P. aeruginosa to persist in nutrient-poor conditions, and provide some of the first evidence that maintaining a mature biofilm is an active process.

microbiology↗