pyoverdine (pVDi) has been reported to act both as a siderophore for scavenging iron (a key nutrient) and a signaling molecule for the expression of virulence factors. this compound is itself part of a core set of virulence factors produced by Pseudomonas aeruginosa during infections. once secreted into the bacterial environment and having scavenged ferric iron, PVDI-Fe 3+ is taken back into the P. aeruginosa periplasm via the outer membrane transporters fpvAi and fpvB. iron release from pVDi in the bacterial periplasm involves numerous proteins encoded by the fpvGHJKCDEF genes and a mechanism of iron reduction. Here, we investigated the global interacting network between these various proteins using systematic bacterial two-hybrid screening. We deciphered a network of five interacting proteins composed of two inner-membrane proteins, FpvG (iron reductase) and FpvH (unknown function), and three periplasmic proteins, FpvJ (unknown function), FpvF (periplasmic PVDI-binding protein), and FpvC (iron periplasmic-binding protein). This interacting network strongly suggests the existence of a large protein machinery composed of these five proteins, all playing a role in iron acquisition by PVDI. Furthermore, we discovered an interaction between the periplasmic siderophore binding protein FpvF and the PvdRT-OpmQ efflux pump, also suggesting a role for FpvF in apo-PVDI recycling and secretion after iron delivery. These results highlight a multi-protein complex that drives iron release from PVDI in the periplasm of P. aeruginosa. Pseudomonas aeruginosa is an opportunistic human Gram-negative pathogen considered by the World Health Organization to be an antibiotic-resistant priority pathogen 1,2. During infections, P. aeruginosa faces a stressful environment and must overcome host-defense mechanisms. To survive within the host, P. aeruginosa secretes a large number of virulence factors, including the siderophores pyoverdines 2,3. Siderophores are small organic compounds produced and secreted by bacteria to access iron 4 , a key nutrient essential for bacterial growth and virulence. Strains unable to produce pyoverdines have been reported to exhibit reduced virulence during infections in mice 5. The role of pyoverdines in the virulence of P. aeruginosa has also been ascertained using rabbit and mouse lung infection models 6-8. Pyoverdines are reported to have a dual role during infection. They are used as a siderophore by P. aeruginosa to scavenge iron from the host proteins 5,8 and also acts as a signaling molecule for the production of two major virulence factors, exotoxin A and the endo-proteinase PrpL 3,9. More generally, all fluorescent Pseudomonas species produce specific pyoverdines as major siderophores to access iron. These pyoverdines are all composed of a peptide of 6 to 12 amino acids, with a specific sequence, and linked to a chromophore derived from 2,3-diamino-6,7-dihydroxyquinoline 10. The sequence of the peptide moiety of the different pyoverdines is very different in amino acid composition and in length amo...
This paper deals with the perception of French natural stop bursts and with the role played by the following vowel in this perception. The first experiment verified the ability of listeners to identify long stimuli containing the burst and part of the subsequent vowel. The second and third experiments investigated the identification of stop bursts with and without a priori knowledge of the following vowel. In order to determine the discriminating power of spectral characteristics of the burst, these experiments used fixed-length burst stimuli of 25-ms duration with all traces of vocalic segment cut off. The bursts of initial voiceless stops were extracted from CVC isolated words. The burst provided very reliable information about stop place since listeners identified correctly 87% of the stops, without a priori knowledge of the following vowel. Performance however was context-dependent. Knowing the identity of the vowel led to a slight but statistically significant improvement in stop identification. Nevertheless, the effects of this knowledge were selective and varied with context. Finally, the first experiment proved that a near perfect identification of stops can be achieved only when all main cues (burst spectrum, burst duration, and onset of vocalic formant transitions) were present simultaneously.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.