Biology subjects

de Oliveira Pereira, T.

Publications and source records attributed to de Oliveira Pereira, T..

3 recordsLinked to original sources

bioRxiv2024

Temperature-responsive control of Pseudomonas aeruginosa virulence determinants through the stabilization of quorum sensing transcriptional regulator RhlR

The versatile bacterium Pseudomonas aeruginosa thrives in diverse environments and is notably recognized for its role as an opportunistic pathogen. In line with its adaptability, P. aeruginosa produces various exoproducts crucial for survival and virulence, several of which regulated through quorum sensing (QS). These factors are also regulated in response to environmental cues, such as temperature changes. As a pathogen, P. aeruginosa is generally thought to activate its virulence factors at temperatures akin to warm-blooded hosts rather than environmental temperatures. Recent studies elucidated the functional structure of the QS transcriptional regulator RhlR, which depends on the stabilizing effects of its cognate autoinducing ligand, N-butanoyl-L-homoserine lactone (C4-HSL), and of the moonlighting chaperone PqsE. Given the influence of temperature on biomolecular dynamics, we investigated how it affects RhlR activity using the RhlR-regulated phzA1 promoter as a proxy. Unexpectedly, we found that RhlR activity is higher at 25{degrees}C than at 37{degrees}C. This temperature-dependent regulation likely stems from altered RhlR turnover, with the presence of PqsE extending RhlR activity tenfold from its basal level at 37{degrees}C to that observed at 25{degrees}C. This lower, environmental-like temperature promotes increased affinity between RhlR and C4-HSL, a trait significantly compromised in the absence of PqsE. These results suggest that this response depends on the structural integrity of the complex, indicating that temperature functions as an additional regulating and stabilizing factor of RhlR function. Accordingly, lower growth temperature fails to increase the activity of a structurally stabilized version of RhlR. The thermoregulation aspect of RhlR activity and signalling impacts the virulence profile of a mutant unable to produce C4-HSL, underscoring its significance in bacterial behaviours and potentially conferring an evolutionary advantage. Author SummaryPseudomonas aeruginosa is recognized for its capacity to colonize vastly different environments, thereby encountering a range of temperatures. The bacteriums ability to adapt to these settings necessitates finely regulated gene expression. Within this regulatory framework lies quorum sensing (QS), the intercellular communication system used by P. aeruginosa to orchestrate the expression of genes responsible for producing diverse exoproducts, including the blue phenazine pyocyanin. RhlR primarily governs the expression of genes required for pyocyanin production, including the phz1 operon. Unlike other QS regulators, RhlR possesses a distinctive characteristic - in addition to its cognate signalling ligand C4-HSL, it depends on the presence of the chaperone-like protein PqsE for stability and activity. This intrinsic instability implies that RhlR may be susceptible to external influences that can modulate its function. Indeed, a lower culture temperature, akin to an environmental-like condition, induces the transcription of the phz1 operon, used as a proxy for RhlR activity. Using a combination of genetic approaches, we present evidence that this thermoregulation is due to an impact on the stability of the RhlR/C4-HSL/PqsE complex. We further show the biological effect of this regulation mechanism in an infection setting, which could underscore a relevant role for other bacterial behaviours.

microbiology↗

bioRxiv2023

Surface growth of Pseudomonas aeruginosa reveals a regulatory effect of 3-oxo-C12-homoserine lactone in absence of its cognate receptor, LasR

Successful colonization of a multitude of ecological niches by the bacterium Pseudomonas aeruginosa relies on its ability to respond to concentrations of self-produced signal molecules. This intercellular communication system known as quorum sensing (QS) tightly regulates the expression of virulence determinants and a diversity of survival functions, including those required for social behaviours. In planktonic cultures of P. aeruginosa, the transcriptional regulator LasR is generally considered on top of the QS circuitry hierarchy; its activation relies on binding to 3-oxo-C12-homoserine lactone (3-oxo-C12-HSL), a product of the LasI synthase. Transcription of lasI is activated by LasR, resulting in a positive feedback loop. Few studies have looked at the function of QS during surface growth even though P. aeruginosa typically lives in biofilm-like communities under natural conditions. Here, we show that surface-grown P. aeruginosa readily produces 3-oxo-C12-HSL in absence of LasR, and that this phenotype is frequent upon surface association in naturally occurring environmental and clinical LasR-defective isolates, suggesting a conserved alternative function for the signal. Indeed, even in the absence of the cognate regulator LasR, 3-oxo-C12-HSL upregulates the autologous expression of pyocyanin and of LasR-controlled virulence determinants in neighboring cells. This highlights a possible role for 3-oxo-C12-HSL in shaping community responses and provides a possible evolutive benefit for mixed populations to carry LasR-defective cells, a common feature of natural of P. aeruginosa. IMPORTANCEThe bacterium Pseudomonas aeruginosa colonizes and thrives in many environments, in which it is typically found in surface-associated polymicrobial communities known as biofilms. Adaptation to this social behavior is aided by quorum sensing (QS), an intercellular communication system pivotal in the expression of social traits. Regardless of its importance in QS regulation, the loss of function of the master regulator LasR is now considered a conserved adaptation of P. aeruginosa, irrespective of the origin of strains. By investigating the QS circuitry in surface-grown cells, we found accumulation of QS signal 3-oxo-C12-HSL in absence of its cognate receptor and activator, LasR. The current understanding of the QS circuit, mostly based on planktonic growing cells, is challenged by investigating the QS circuitry of surface-grown cells. This provides a new perspective on the beneficial aspects that underline the frequency of LasR-deficient isolates.

microbiology↗

bioRxiv2017

c-di-GMP-linked phenotypes are modulated by the interaction between a diguanylate cyclase and a polar hub protein

c-di-GMP is a major player in the decision between biofilm and motile lifestyles. Several bacteria present a large number of c-di-GMP metabolizing proteins, thus a fine-tuning of this nucleotide levels may occur. It is hypothesized that some c-di-GMP metabolizing proteins would provide the global c-di-GMP levels inside the cell whereas others would maintain a localized pool, with the resulting c-di-GMP acting at the vicinity of its production. Although attractive, this hypothesis has yet to be proven in Pseudomonas aeruginosa. We found that the diguanylate cyclase DgcP interacts with the cytosolic region of FimV, a peptidoglycan-binding protein involved in type IV pilus assembly. Moreover, DgcP is located at the cell poles in wild type cells, but scattered in the cytoplasm of cells lacking FimV. Overexpression of DgcP leads to the classical phenotypes of high c-di-GMP levels (increased biofilm and impaired motilities) in the wild-type strain, but not in a AfimV background. Therefore, our findings strongly suggest that DgcP is regulated by FimV and may provide the local c-di-GMP pool that can be sensed by other proteins at the cell pole, bringing to light a specialized function for a specific diguanylate cyclase.

microbiology↗