Shigella species are able to grow in a variety of environments, including intracellularly in host epithelial cells. Shigella have a number of different iron transport systems that contribute to their ability to grow in these diverse environments. Siderophore iron uptake systems, heme transporters, and ferric and ferrous iron transport systems are present in these bacteria, and the genes encoding some of these systems appear to have spread among the Shigella species by horizontal transmission. Iron is not only essential for growth of Shigella but also plays an important role in regulation of metabolic processes and virulence determinants in Shigella. This regulation is mediated by the repressor protein Fur and the small RNA RyhB.
The opportunistic pathogen Pseudomonas aeruginosa causes a variety of infections in immunocompromised individuals, including individuals with the heritable disease cystic fibrosis. Like the carbon sources metabolized by many disease-causing bacteria, the carbon sources metabolized by P. aeruginosa at the host infection site are unknown. We recently reported that L-alanine is a preferred carbon source for P. aeruginosa and that two genes potentially involved in alanine catabolism (dadA and dadX) are induced during in vivo growth in the rat peritoneum and during in vitro growth in sputum (mucus) collected from the lungs of individuals with cystic fibrosis. The goals of this study were to characterize factors required for alanine catabolism in P. aeruginosa and to assess the importance of these factors for in vivo growth. Our results reveal that dadA and dadX are arranged in an operon and are required for catabolism of L-alanine. The dad operon is inducible by L-alanine, D-alanine, and L-valine, and induction is dependent on the transcriptional regulator Lrp. Finally, we show that a mutant unable to catabolize DL-alanine displays decreased competitiveness in a rat lung model of infection.A hallmark of successful bacterial pathogens is their ability to replicate within their hosts, where they not only must acquire nutrients for growth but also often compete with commensal microorganisms. Although this basic tenet of bacterial pathogenesis, which was espoused originally by Louis Pasteur in the late nineteenth century (21) and more recently by E. D. Garber and other workers (3, 6), has been recognized for some time, it has generally been overlooked, and the metabolic pathways critical for proliferation in most infection sites are unknown. Basic knowledge regarding metabolic processes utilized by infecting bacteria is of fundamental importance for understanding bacterial pathogenesis and may offer opportunities for development of novel therapeutics. Indeed, interfering with bacterial metabolism in vivo has been efficacious for inhibiting the pathogenesis of several bacterial pathogens. For example, mutants of the poultry pathogen Campylobacter jejuni that are unable to catabolize L-serine display markedly reduced colonization of the chick gut (32). Likewise, loss of threonine utilization by the pulmonary pathogen Legionella pneumophila prevents replication in alveolar macrophages (26).The gram-negative opportunistic pathogen Pseudomonas aeruginosa is a leading cause of ophthalmic, burn wound, and nosocomial infections and causes chronic pulmonary infections in individuals with cystic fibrosis (CF) (9). In addition, P. aeruginosa colonizes numerous environments outside the host, and its ability to catabolize a wide array of carbon sources likely allows proliferation in these diverse environments. From a host-pathogen perspective, the carbon sources available for growth significantly affect production of extracellular virulence factors and biofilm formation in P. aeruginosa (19,20,29). Despite these findings, we have lit...
Shigella spp . have transport systems for both ferric and ferrous iron. The iron can be taken up as free iron or complexed to a variety of carriers. All Shigella species have both the Feo and Sit systems for acquisition of ferrous iron, and all have at least one siderophore-mediated system for transport of ferric iron. Several of the transport systems, including Sit, Iuc/IutA (aerobactin synthesis and transport), Fec (ferric di-citrate uptake), and Shu (heme transport) are encoded within pathogenicity islands. The presence and the genomic locations of these islands vary considerably among the Shigella species, and even between isolates of the same species. The expression of the iron transport systems is influenced by the concentration of iron and by environmental conditions including the level of oxygen. ArcA and FNR regulate iron transport gene expression as a function of oxygen tension, with the sit and iuc promoters being highly expressed in aerobic conditions, while the feo ferrous iron transporter promoter is most active under anaerobic conditions. The effects of oxygen are also seen in infection of cultured cells by Shigella flexneri; the Sit and Iuc systems support plaque formation under aerobic conditions, whereas Feo allows plaque formation anaerobically.
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 đź’™ for researchers
Part of the Research Solutions Family.