bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2025.03.17.643737

Modulation of the Pseudomonas aeruginosa quorum sensing cascade by MexT-regulated factors

Frando, A.·Parsek, R. S.·Omar, J.·Smalley, N. E.·Dandekar, A. A.
View original source ↗Export metadata ↓

Abstract

Pseudomonas aeruginosa (Pa) uses quorum sensing (QS), a cell-cell communication system that enables it to sense cell density and to alter gene expression. Pa has three complete QS circuits controlled by the regulators LasR, RhlR, and PqsR, that together activate hundreds of genes. In the well-studied strain PAO1, QS is organized hierarchically, with PqsR and RhlR activity dependent on LasR. This hierarchy depends on the non-QS transcription factor MexT; deletion of mexT allows for RhlR activity in the absence of LasR. We aimed to identify how MexT modulates the Pa QS architecture. We compared the transcriptome of PAO1 to that of PAO1{Delta}mexT and determined a MexT regulon. We identified two MexT-regulated operons that may affect the QS hierarchy: the efflux pump genes mexEF-oprN and the Pseudomonas quinolone signal (PQS) synthesis genes pqsABCDE. We tested whether the products of these genes affected the QS hierarchy. A mexEF knockout mutant, like a mexT deletion mutant, exhibited RhlR activity earlier, and to a higher magnitude, than wild-type PAO1. MexEF-OprN is known to export quinolones, and we found that exogenous addition of PQS, through PqsE, also resulted in earlier and higher magnitude of RhlR activity compared to wild-type PAO1. We also discovered alternate QS architectures in clinical isolates, where RhlR activity is not fully dependent on LasR. In these isolates, surprisingly, MexT does not influence the relationship between LasR and RhlR. Our work reveals a new suite of factors that regulate QS in Pa, with implications for bacterial behaviors in environmental and clinical settings. ImportanceBacteria interact with both abiotic and biotic factors in their environment. Quorum sensing (QS) is one mechanism that bacteria use to communicate with other bacteria and coordinate behaviors in the population. QS regulates a wide variety of processes ranging from the production of light to modulation of virulence factors; some bacteria use single QS circuits, while others have several. The opportunistic pathogen Pseudomonas aeruginosa uses QS to control some virulence functions and has three complete QS circuits. Our study explores why bacteria might have multiple QS circuits. We show how a non-QS transcription factor, MexT, influences QS regulators in P. aeruginosa and we uncover the diversity of QS architectures in clinical isolates. This study begins to reveal the benefits (or disadvantages) of multiple QS circuits, allowing us to understand behaviors of bacteria that have a range of implications including in health, agriculture, and bioremediation.

Source connections

Explore related subjects

microbiologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Frando, A., Parsek, R. S., Omar, J., Smalley, N. E., Dandekar, A. A.. 2025-03-17. Modulation of the Pseudomonas aeruginosa quorum sensing cascade by MexT-regulated factors. https://doi.org/10.1101/2025.03.17.643737

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Matrix-controlled emergence of biofilm architecture shapes antimicrobial survival

Biofilms are structured microbial communities whose extracellular matrix is widely regarded as a basis of their protection against antimicrobial compounds. Yet how matrix production by individual bacteria gives rise to collective architecture and antimicrobial protection remains poorly understood. Here, we systematically varied expression of the master biofilm regulator csgD in Salmonella enterica and found that increasing matrix production reorganizes biofilms from dense, isotropic packings into sparse, nematically aligned communities by altering cell-cell interactions. By combining experimentally measured biofilm architectures with reaction-diffusion modeling, we show that these structural changes produce distinct patterns of antimicrobial killing, ranging from preferential killing near the liquid-biofilm interface to more uniform killing throughout the community. Consequently, increasing matrix production unexpectedly reduces antimicrobial survival by shifting the biofilm into different transport regimes, while strain-specific physiological differences further modulate antimicrobial depletion. Rather than acting as a passive barrier, EPS therefore shapes antimicrobial susceptibility by reorganizing biofilm architecture and its transport properties. EPS thus provides a physical link between molecular regulation, collective architecture and antimicrobial survival, providing a quantitative framework for understanding how cellular matrix production generates emergent biofilm function.

microbiology↗
bioRxiv2026

Mapping virulence-associated protein interaction networks reveals regulators of thermotolerance in Cryptococcus neoformans

Protein-protein interactions (PPIs) influence critical biological processes in pathogenic microorganisms, such as the human fungal pathogen, Cryptococcus neoformans. Fungal thermotolerance and stress response pathways are key virulence determinants that directly impact pathogen adaptation and survival and the infection process. To establish a comprehensive baseline of PPIs in C. neoformans and explore these interactions to infer functional roles for uncharacterized proteins, we applied size exclusion chromatography coupled with mass spectrometry to the secreted and cellular proteomes of the fungi. As a result, 216 and 1699 unique proteins were identified across 24 secretome and proteome fractions, respectively. The predicted secretome networks included expected proteins associated with vesicles and virulence, indicating a role in extracellular defense. Whereas the cryptococcal proteome highlighted interactions among proteins with defined roles in fungal virulence for protein stability and thermotolerance, including two previously uncharacterized proteins, CNAG_00287 and CNAG_05199, putatively involved in complex formation with heat-shock proteins (HSP). Based on sequence and structure homology, we propose that CNAG_00287 is a tetratricopeptide repeat-containing co-chaperone that modulates Hsp 70 activity and CNAG_05199 functions as a Hsp70. We validated the thermotolerance role of CNAG_00287 in heat-related stress, as its absence significantly impaired fungal growth in nutrient-limited media at 37 {degrees}C. Together, this work resolves virulence-associated PPIs within C. neoformans and reveals new molecular regulators of thermotolerance that underpin fungal pathogenicity.

microbiology↗
bioRxiv2026

Environmental filtering and host identity collectively shape root-associated microbiomes of Ericaceae and ectomycorrhizal plants in fumarole fields

Background Symbiosis with microbes is a key strategy that has enabled plants to colonize extreme environments. Since the benefits conferred by root-associated microbes depend on both environmental conditions and host-microbe combinations, plant adaptation to harsh environments is closely linked to the assembly of root microbial communities. Understanding how environmental and host filtering jointly shape these communities is therefore fundamental to elucidating the mechanisms underlying plant adaptation to extreme environments. Results In this study, we investigated the differentiation of root-associated prokaryotic and fungal communities and individual operational taxonomic units (OTUs) across two contrasting habitats surrounding fumaroles, solfatara-field and forest-edge habitats, and six dominant Ericaceae and ectomycorrhizal plant taxa. Prokaryotic and fungal OTUs rarely exhibited strong preferences for both habitat and host identity. Instead, many of prokaryotic and fungal OTUs specialized to one of these niches, collectively generating root microbial communities differentiated by both factors. Nonetheless, striking specializations in habitat and host niches were observed in the fungal family Hyaloscyphaceae (Helotiales). To gain insight into the evolutionary basis of microbial specialization, we examined phylogenetic signals in preference phenotypes. The resulting weak phylogenetic signals in these preference phenotypes further suggest that this fungal clade has undergone substantial ecological divergence. Conclusion Overall, our findings indicate that root-associated microbial communities in extreme environments are assembled through the accumulation of microbial taxa specialized to either habitat or host, and that strong ecological specialization in fungi can arise with little phylogenetic constraint.

microbiology↗