Biology subjects

Colomer-Winter, C.

Publications and source records attributed to Colomer-Winter, C..

5 recordsLinked to original sources

bioRxiv2025

A two-component system signaling hub controls enterococcal membrane remodeling in response to daptomycin

Daptomycin is a last resort antibiotic used to treat vancomycin-resistant enterococcal infections, but daptomycin resistance (DAPR) arises quickly during treatment. Resistance is due to sequential acquisition of point mutations in the two-component system LiaFSR and in cardiolipin synthases and is associated with alteration of phospholipid and glycolipid membrane composition. The molecular mechanisms underlying these lipid changes are currently unknown. Similarly, it is unclear why mutations in liaFSR occur prior to mutations in cls. We discovered that Enterococcus faecalis remodels membrane composition as a phenotypic response to daptomycin that parallels the membrane composition of DAPR strains. The enrichment in glycolipids that follows antibiotic exposure is due to LtaS1, the main LTA synthase of E. faecalis. Moreover, LtaS1 activity is governed by a network of two-component systems formed by LiaFSR, SapRS, and BsrRS that couple antibiotic sensing with membrane lipid remodeling. Together, our results provide a unifying mechanism that drives phenotypic membrane fortification in a Gram-positive pathogen which simultaneously predisposes the cell to acquire genetic high-level daptomycin resistance. Significance StatementDaptomycin is the preferred alternative to treat vancomycin-resistant Enterococcus infections. However, the efficacy of daptomycin is limited by the acquisition of daptomycin resistance. Alterations in lipid membrane composition represent a conserved strategy to fortify the Gram-positive membrane. We discovered that E. faecalis phenotypically remodels membrane composition in response to daptomycin and that the enrichment in glycolipids is dependent on LTA synthesis. We expand our limited knowledge of enterococcal LTA synthases, confirming LtaS1 as the main LTA synthase and placing LTA biogenesis under control of a network of antibiotic-responsive two-component systems. Our work provides a molecular explanation for the sequential evolution of daptomycin resistance and may support the use of existing LtaS inhibitors to prevent acquisition of daptomycin resistance.

microbiology↗

bioRxiv2025

Adaptation of Enterococcus faecalis to intestinal mucus revealed by a human colonic organoid model

The human gastrointestinal tract hosts a diverse population of microorganisms that have a significant impact on host health. Among this population, Enterococcus faecalis (Ef) represents a common member of intestinal microbiota colonizing humans early in life, but which can also opportunistically infect its host. Despite its importance in human health, investigations of its physiological adaptation to the mucosal environment remain limited. Building on recent advances in tissue engineering, we here leverage human colonic organoids (colonoids) to investigate the Efs mechanisms of mucosal surface colonization across space and time. Using high-resolution microscopy, we visualized Ef growth within the natively formed colonic mucus layer in colonoids. Leveraging a custom perfusion chamber, we tracked Ef growth within the mucus of live colonoids over time under flow, which revealed specific colonization strategies, including biofilm-like microcolony formation. To identify Ef fitness determinants in this niche, we implemented transposon insertion sequencing (Tn-seq) in the natively formed mucus of live colonoids. This approach revealed a large fitness rearrangement compared to typical liquid culture, mainly involving metabolic activity and regulatory response during mucosal colonization, as well as factors that may contribute to colony formation at the mucosal surface. Altogether, our results show important physiological and biophysical adaptation of Ef to the mucosal surface that are not captured by in vitro conditions and that cannot be revealed in vivo at high resolution.

microbiology↗

bioRxiv2022

Identification of Multiple Iron Uptake Mechanisms in Enterococcus faecalis and Their Relationship to Virulence

Among the unfavorable conditions bacteria encounter within the host is restricted access to essential trace metals such as iron. To overcome iron deficiency, bacteria deploy multiple strategies to scavenge iron from host tissues with abundant examples of iron acquisition systems being implicated in bacterial pathogenesis. Yet, the mechanisms utilized by the major nosocomial pathogen Enterococcus faecalis to maintain intracellular iron balance are poorly understood. In this report, we conducted a systematic investigation to identify and characterize the iron acquisition mechanisms of E. faecalis and to determine their contribution to virulence. Bioinformatic analysis and literature surveys revealed that E. faecalis possesses three conserved iron uptake systems. Through transcriptomics, we discovered two novel ABC-type transporters that mediate iron uptake. While inactivation of a single transporter had minimal impact on the ability of E. faecalis to maintain iron homeostasis, inactivation of all five systems ({Delta}5Fe strain) disrupted intracellular iron homeostasis and considerably impaired cell growth under iron-deficiency. Virulence of the {Delta}5Fe strain was generally impaired in different animal models but showed niche-specific variations in mouse models, leading us to suspect that heme can serve as an iron source to E. faecalis during mammalian infections. Indeed, heme supplementation restored growth of {Delta}5Fe under iron-depletion and virulence in an invertebrate infection model. Collectively, this study reveals that the collective contribution of five iron transporters promotes E. faecalis virulence and that the ability to acquire and utilize heme as an iron source is critical to the systemic dissemination of E. faecalis.

microbiology↗

bioRxiv2019

(p)ppGpp and CodY promote Enterococcus faecalis virulence in a murine model of catheter-associated urinary tract infection

In Firmicutes, the nutrient-sensing regulators (p)ppGpp, the effector molecule of the stringent response, and CodY work in tandem to maintain bacterial fitness during infection. Here, we tested (p)ppGpp and codY mutant strains of Enterococcus faecalis in a catheter-associated urinary tract infections (CAUTI) mouse model and used global transcriptional analysis to investigate the (p)ppGpp and CodY relationship. Absence of (p)ppGpp or single inactivation of codY led to lower bacterial loads in catheterized bladders, and diminished biofilm formation on fibrinogen-coated surfaces under in vitro and in vivo conditions. Single inactivation of the bifunctional (p)ppGpp synthetase/hydrolase rel did not affect virulence supporting previous evidence that association of (p)ppGpp with enterococcal virulence is not dependent on activation of the stringent response. Inactivation of codY in the (p)ppGpp0 strain restored E. faecalis virulence in the CAUTI model as well as the ability to form biofilms in vitro. Transcriptome analysis revealed that inactivation of codY restores, for the most part, the dysregulated metabolism of (p)ppGpp0 cells. While a clear linkage between (p)ppGpp and CodY with expression of virulence factors could not be established, targeted transcriptional analysis indicate that a possible association between (p)ppGpp and c-di-AMP signaling pathways in response to the conditions found in the bladder may plays a role in enterococcal CAUTI. Collectively, this study identifies the (p)ppGpp-CodY network as an important contributor to enterococcal virulence in catheterized mouse bladder and supports that basal (p)ppGpp pools and CodY promote virulence through maintenance of a balanced metabolism during adverse conditions.\n\nImportanceCatheter-associated urinary tract infections (CAUTI) are one of the most frequent types of infection found in the hospital setting that can develop into serious and potentially fatal bloodstream infections. One of the infectious agents that frequently cause complicated CAUTI is the bacterium Enterococcus faecalis, a leading cause of hospital-acquired infections that are often difficult to treat due to the exceptional multidrug resistance of some isolates. Understanding the mechanisms by which E. faecalis causes CAUTI will aid in the discovery of new druggable targets to treat these infections. In this study, we report the importance of two nutrient-sensing bacterial regulators, named (p)ppGpp and CodY, for the ability of E. faecalis to infect the catheterized bladder of mice.

microbiology↗

bioRxiv2018

Manganese acquisition is essential for virulence of Enterococcus faecalis

Manganese (Mn) is an essential micronutrient that is not readily available to pathogens during infection due to an active host defense mechanism known as nutritional immunity. To overcome this nutrient restriction, bacteria utilize high-affinity transporters that allow them to compete with host metal-binding proteins. Despite the established role of Mn in bacterial pathogenesis, little is known about the relevance of Mn in the pathophysiology of E. faecalis. Here, we identified and characterized the major Mn acquisition systems of E. faecalis. We discovered that the ABC-type permease EfaCBA and two Nramp-type transporters, named MntH1 and MntH2, work collectively to promote cell growth under Mn-restricted conditions. The simultaneous inactivation of EfaCBA, MntH1 and MntH2 ({Delta}efa{Delta}mntH1{Delta}mntH2 strain) led to drastic reductions (>95%) in intracellular Mn content, severe growth defects in body fluids (serum and urine) ex vivo, significant loss of virulence in Galleria mellonella, and virtually complete loss of virulence in rabbit endocarditis and murine catheter-associated urinary tract infection (CAUTI) models. Despite the functional redundancy of EfaCBA, MntH1 and MntH2 under in vitro or ex vivo conditions and in the invertebrate model, dual inactivation of efaCBA and mntH2 ({Delta}efa{Delta}mntH2 strain) was sufficient to prompt maximal sensitivity to calprotectin, a Mn- and Zn-chelating host antimicrobial protein, and for the loss of virulence in mammalian models. Interestingly, EfaCBA appears to play a prominent role during systemic infection, whereas MntH2 was more important during CAUTI. The different roles of EfaCBA and MntH2 in these sites could be attributed, at least in part, to the differential expression of efaA and mntH2 in cells isolated from hearts or from bladders. Collectively, this study demonstrates that Mn acquisition is essential for the pathogenesis of E. faecalis and validates Mn uptake systems as promising targets for the development of new antimicrobials.

microbiology↗