Biology subjects

Meirelles, L. A.

Publications and source records attributed to Meirelles, L. A..

5 recordsLinked to original sources

bioRxiv2026

Pyocyanin disrupts airway regeneration to favor chronic Pseudomonas aeruginosa infection

During chronic infections, host tissues undergo repeated cycles of injury and repair while being exposed to bacterial products. Although many virulence factors trigger immune responses, whether bacterial metabolites alter tissue architecture by disrupting regenerative programs remains largely unexplored. Here, using a primary-cell-derived human lung microtissue model, we show that the redox-active metabolite pyocyanin (PYO), produced by the opportunistic pathogen Pseudomonas aeruginosa, disrupts airway epithelial regeneration and reshapes tissue architecture, amplifying infection. PYO exposure impairs epithelial repair, leading to defects in mucociliary clearance and promoting bacterial growth. Single-cell transcriptomics and imaging reveal that PYO exposure during basal cell differentiation alters epithelial cell-type composition. Keratin-13-rich cells promote the emergence of squamous regions with defective ciliogenesis, resulting in functional defects. After characterizing how PYO remodels the epithelium, we tested how these changes impact bacterial fitness. Using transposon-insertion sequencing and live imaging of infections, we show that these regeneration defects improve the fitness of mutants that tend to form biofilms, a common feature of chronic infections. Together, our results reveal that PYO reshapes regenerative trajectories and tissue architecture in ways that subsequently alter infection outcomes, highlighting the role of secreted metabolites as potential modulators of tissue regeneration during chronic lung infections.

microbiology↗

bioRxiv2026

Pseudomonas aeruginosa balances cytotoxicity and motility to counter phagocytosis by macrophages

During chronic lung infections, Pseudomonas aeruginosa diversifies under selection from antibiotics, metabolic constraints, and host defenses. Macrophages are key sentinels of the innate immune system and play a central role in clearing airway pathogens. Yet, how they process heterogeneous bacterial populations remains poorly understood. Here, we investigate how P. aeruginosa evades phagocytosis under conditions that mimic chronic infection. We use an attenuated mutant lacking a functional type III secretion system (T3SS), which reduces macrophage killing, allowing us to isolate determinants of bacterial susceptibility to phagocytosis. Using transposon insertion sequencing (Tn-seq), we identify bacterial fitness factors under phagocytic selection. Our screen reveals that disruption of genes involved in swimming and twitching motility reduces uptake by macrophages. We find that motility defects interfere with the physical interactions between bacteria and macrophages. Live-cell imaging shows that motility-deficient bacteria exhibit reduced surface exploration and unstable attachment to macrophages, limiting their internalization. Clinical isolates with reduced swimming or twitching motility display similarly impaired uptake. Restoring T3SS activity in these motility mutants rescues cytotoxicity toward macrophages, with one notable exception: flagellum-less, hyper-piliated P. aeruginosa remains avirulent and resistant to phagocytosis due to their lack of engagement with macrophages. Together, these results support two distinct immune evasion strategies: during chronic infection, reduced motility promotes a "freeze"-like state that limits detection and engulfment, whereas during acute infection, P. aeruginosa adopts a "fight"-like strategy by activating its T3SS to eliminate macrophages. SummaryHow immune cells recognize and eliminate bacteria is typically explained by molecular signaling, yet the role of physical interactions remains unclear. We show that bacterial motility is a key determinant of phagocytosis by macrophages. Using functional genomics and live imaging, we find that swimming and twitching motility promote bacterial uptake by enabling effective surface exploration and stable physical engagement with macrophages. Loss of motility commonly observed in chronic P. aeruginosa infections reduces these interactions and allows bacteria to evade engulfment. In contrast, during acute infection, bacteria rely on T3SS-mediated killing of macrophages, independently of motility. These findings reveal that phagocytosis is governed not only by immune recognition but also by bacterial mechanical behavior, and identify a shift in host-pathogen interactions associated with chronic versus acute infection. More broadly, this work establishes mechanics as an important dimension of immune evasion.

microbiology↗

bioRxiv2024

Pseudomonas aeruginosa faces a fitness trade-off between mucosal colonization and antibiotic tolerance during airway infections

Pseudomonas aeruginosa causes antibiotic-resilient acute and chronic pneumonia, but the mechanisms by which it adapts to the airway environment are poorly understood. Here, we investigated P. aeruginosa pathoadaptive mechanisms in tissue-engineered human airway organoids. Using transposon sequencing in situ, we decoded how P. aeruginosa survives on the mucosal surface during antibiotic treatment. Biofilm formation emerged as a major driver of P. aeruginosa colonization. Mutants that extensively produce biofilms on mucus show limited exploratory behavior, which limits nutrient access, slowing down their growth. Conversely, biofilm-dwelling P. aeruginosa better tolerate antibiotics via biophysical mechanisms. Finally, biofilms can shelter less-tolerant but more cytotoxic strains, thereby contributing to genotypic heterogeneity. P. aeruginosa must therefore adapt to conflicting physical and biological selective pressures to initiate chronic infections.

microbiology↗

bioRxiv2021

Redox-active secondary metabolites act as interspecies modulators of antibiotic resilience

Bacterial opportunistic pathogens make a wide range of secondary metabolites both in the natural environment and when causing infections, yet how these molecules mediate microbial interactions and their consequences for antibiotic treatment are still poorly understood. Here, we explore the role of two redox-active secondary metabolites, pyocyanin and toxoflavin, as interspecies modulators of antibiotic resilience. We find that these molecules dramatically change susceptibility levels of diverse bacteria to clinical antibiotics. Pyocyanin is made by Pseudomonas aeruginosa, while toxoflavin is made by Burkholderia gladioli, organisms that infect cystic fibrosis and other immunocompromised patients. Both molecules alter the susceptibility profile of pathogenic species within the "Burkholderia cepacia complex" to different antibiotics, either antagonizing or potentiating their effects, depending on the drugs class. Defense responses regulated by the redox-sensitive transcription factor SoxR potentiate the antagonistic effects these metabolites have against fluoroquinolones, and the presence of genes encoding SoxR and the efflux systems it regulates can be used to predict how these metabolites will affect antibiotic susceptibility of different bacteria. Finally, we demonstrate that inclusion of secondary metabolites in standard protocols used to assess antibiotic resistance can dramatically alter the results, motivating the development of new tests for more accurate clinical assessment.

microbiology↗

bioRxiv2020

Bacterial defenses against a natural antibiotic promote collateral resilience to clinical antibiotics

As antibiotic-resistant infections become increasingly prevalent worldwide, understanding the factors that lead to antimicrobial treatment failure is essential to optimizing the use of existing drugs. Opportunistic human pathogens in particular typically exhibit high levels of intrinsic antibiotic resistance and tolerance1, leading to chronic infections that can be nearly impossible to eradicate2. We asked whether the recalcitrance of these organisms to antibiotic treatment could be driven in part by their evolutionary history as environmental microbes, which frequently produce or encounter natural antibiotics3,4. Using the opportunistic pathogen Pseudomonas aeruginosa as a model, we demonstrate that the self-produced natural antibiotic pyocyanin (PYO) activates bacterial defenses that confer collateral tolerance to certain synthetic antibiotics, including in a clinically-relevant growth medium. Non-PYO-producing opportunistic pathogens isolated from lung infections similarly display increased antibiotic tolerance when they are co-cultured with PYO-producing P. aeruginosa. Furthermore, we show that beyond promoting bacterial survival in the presence of antibiotics, PYO can increase the apparent rate of mutation to antibiotic resistance by up to two orders of magnitude. Our work thus suggests that bacterial production of natural antibiotics in infections could play an important role in modulating not only the immediate efficacy of clinical antibiotics, but also the rate at which antibiotic resistance arises in multispecies bacterial communities.

microbiology↗