scholarly journals Interplay between Manganese and Iron in Pneumococcal Pathogenesis: Role of the Orphan Response Regulator RitR

2012 ◽  
Vol 81 (2) ◽  
pp. 421-429 ◽  
Author(s):  
Cheryl-Lynn Y. Ong ◽  
Adam J. Potter ◽  
Claudia Trappetti ◽  
Mark J. Walker ◽  
Michael P. Jennings ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Iron Uptake ◽  
Metal Ion ◽  
Response Regulator ◽  
Transport Systems ◽  
Bacterial Cells ◽  
Content Type ◽  
Manganese Ion ◽  
Iron And Manganese

ABSTRACTStreptococcus pneumoniae(the pneumococcus) is a major human pathogen that is carried asymptomatically in the nasopharynx by up to 70% of the human population. Translocation of the bacteria into internal sites can cause a range of diseases, such as pneumonia, otitis media, meningitis, and bacteremia. This transition from nasopharynx to growth at systemic sites means that the pneumococcus needs to adjust to a variety of environmental conditions, including transition metal ion availability. Although it is an important nutrient, iron potentiates oxidative stress, and it is established that inS. pneumoniae, expression of iron transport systems and proteins that protect against oxidative stress are regulated by an orphan response regulator, RitR. In this study, we investigated the effect of iron and manganese ion availability on the growth of aritRmutant. Deletion ofritRled to impaired growth of bacteria in high-iron medium, but this phenotype could be suppressed with the addition of manganese. Measurement of metal ion accumulation indicated that manganese prevents iron accumulation. Furthermore, the addition of manganese also led to a reduction in the amount of hydrogen peroxide produced by bacterial cells. Studies of virulence in a murine model of infection indicated that RitR was not essential for pneumococcal survival and suggested that derepression of iron uptake systems may enhance the survival of pneumococci in some niches.

scholarly journals Disruption of a Novel Iron Transport System Reverses Oxidative Stress Phenotypes of a dpr Mutant Strain of Streptococcus mutans

2018 ◽  
Vol 200 (14) ◽  
Author(s):  
Tridib Ganguly ◽  
Jessica K. Kajfasz ◽  
James H. Miller ◽  
Eric Rabinowitz ◽  
Lívia C. C. Galvão ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Streptococcus Mutans ◽  
Hydroxyl Radicals ◽  
Transport System ◽  
Iron Uptake ◽  
Iron Transport ◽  
Transport Systems ◽  
Phenotypic Characterization ◽  
Content Type

ABSTRACT The Dps-like peroxide resistance protein (Dpr) is essential for H 2 O 2 stress tolerance and aerobic growth of the oral pathogen Streptococcus mutans . Dpr accumulates during oxidative stress, protecting the cell by sequestering iron ions and thereby preventing the generation of toxic hydroxyl radicals that result from the interaction of iron with H 2 O 2 . Previously, we reported that the SpxA1 and SpxA2 regulators positively regulate expression of dpr in S. mutans . Using an antibody raised against S. mutans Dpr, we confirmed at the protein level the central and cooperative nature of SpxA1 and SpxA2 regulation in Dpr production. During phenotypic characterization of the S. mutans Δ dpr strain, we observed the appearance of distinct colony variants, which sometimes lost the oxidative stress sensitivity typical of Δ dpr strains. Whole-genome sequencing of these phenotypically distinct Δ dpr isolates revealed that a putative iron transporter operon, smu995-smu998 , was a genomic hot spot with multiple single nucleotide polymorphisms identified within the different isolates. Deletion of smu995 or the entire smu995-smu998 operon in the Δ dpr background strain completely reversed the oxidative stress-sensitive phenotypes associated with dpr inactivation. Conversely, inactivation of genes encoding the ferrous iron transport system FeoABC did not alleviate phenotypes of the Δ dpr strain. Preliminary characterization of strains lacking smu995-smu998 , feoABC , and the iron/manganese transporter gene sloABC revealed the interactive nature of these three systems in iron transport but also indicated that there may be additional iron uptake systems in S. mutans . IMPORTANCE The dental caries-associated pathogen Streptococcus mutans routinely encounters oxidative stress within the human plaque biofilm. Previous studies revealed that the iron-binding protein Dpr confers protection toward oxidative stress by limiting free iron availability, which is associated with the generation of toxic hydroxyl radicals. Here, we report the identification of spontaneously occurring mutations within Δ dpr strains. Several of those mutations were mapped to the operon smu995-smu998 , revealing a previously uncharacterized system that appears to be important in iron acquisition. Disruption of the smu995-smu998 operon resulted in reversion of the stress-sensitive phenotype typical of a Δ dpr strain. Our data suggest that the Smu995-Smu998 system works along with other known metal transport systems of S. mutans , i.e., FeoABC and SloABC, to coordinate iron uptake.

scholarly journals Spo0A Suppresses sin Locus Expression in Clostridioides difficile

mSphere ◽  
2020 ◽  
Vol 5 (6) ◽  
Author(s):  
Babita Adhikari Dhungel ◽  
Revathi Govind
Keyword(s):  
Diarrheal Disease ◽  
Toxin Production ◽  
The United States ◽  
Upstream Region ◽  
Pcr Analysis ◽  
Bacterial Cells ◽  
Master Regulator ◽  
Content Type ◽  
Clostridioides Difficile

ABSTRACT Clostridioides difficile is the leading cause of nosocomial infection and is the causative agent of antibiotic-associated diarrhea. The severity of the disease is directly associated with toxin production, and spores are responsible for the transmission and persistence of the organism. Previously, we characterized sin locus regulators SinR and SinR′ (we renamed it SinI), where SinR is the regulator of toxin production and sporulation. The SinI regulator acts as its antagonist. In Bacillus subtilis, Spo0A, the master regulator of sporulation, controls SinR by regulating the expression of its antagonist, sinI. However, the role of Spo0A in the expression of sinR and sinI in C. difficile had not yet been reported. In this study, we tested spo0A mutants in three different C. difficile strains, R20291, UK1, and JIR8094, to understand the role of Spo0A in sin locus expression. Western blot analysis revealed that spo0A mutants had increased SinR levels. Quantitative reverse transcription-PCR (qRT-PCR) analysis of its expression further supported these data. By carrying out genetic and biochemical assays, we show that Spo0A can bind to the upstream region of this locus to regulates its expression. This study provides vital information that Spo0A regulates the sin locus, which controls critical pathogenic traits such as sporulation, toxin production, and motility in C. difficile. IMPORTANCE Clostridioides difficile is the leading cause of antibiotic-associated diarrheal disease in the United States. During infection, C. difficile spores germinate, and the vegetative bacterial cells produce toxins that damage host tissue. In C. difficile, the sin locus is known to regulate both sporulation and toxin production. In this study, we show that Spo0A, the master regulator of sporulation, controls sin locus expression. Results from our study suggest that Spo0A directly regulates the expression of this locus by binding to its upstream DNA region. This observation adds new detail to the gene regulatory network that connects sporulation and toxin production in this pathogen.

scholarly journals Role of hepcidin in oxidative stress and cell death of cultured mouse renal collecting duct cells: protection against iron and sensitization to cadmium

2021 ◽  
Author(s):  
Stephanie Probst ◽  
Johannes Fels ◽  
Bettina Scharner ◽  
Natascha A. Wolff ◽  
Eleni Roussa ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cell Death ◽  
Cell Fate ◽  
Catalase Activity ◽  
Metal Ion ◽  
Iron Homeostasis ◽  
Collecting Duct ◽  
Duct Cell ◽  
Plasmid Transfection

AbstractThe liver hormone hepcidin regulates systemic iron homeostasis. Hepcidin is also expressed by the kidney, but exclusively in distal nephron segments. Several studies suggest hepcidin protects against kidney damage involving Fe2+ overload. The nephrotoxic non-essential metal ion Cd2+ can displace Fe2+ from cellular biomolecules, causing oxidative stress and cell death. The role of hepcidin in Fe2+ and Cd2+ toxicity was assessed in mouse renal cortical [mCCD(cl.1)] and inner medullary [mIMCD3] collecting duct cell lines. Cells were exposed to equipotent Cd2+ (0.5–5 μmol/l) and/or Fe2+ (50–100 μmol/l) for 4–24 h. Hepcidin (Hamp1) was transiently silenced by RNAi or overexpressed by plasmid transfection. Hepcidin or catalase expression were evaluated by RT-PCR, qPCR, immunoblotting or immunofluorescence microscopy, and cell fate by MTT, apoptosis and necrosis assays. Reactive oxygen species (ROS) were detected using CellROX™ Green and catalase activity by fluorometry. Hepcidin upregulation protected against Fe2+-induced mIMCD3 cell death by increasing catalase activity and reducing ROS, but exacerbated Cd2+-induced catalase dysfunction, increasing ROS and cell death. Opposite effects were observed with Hamp1 siRNA. Similar to Hamp1 silencing, increased intracellular Fe2+ prevented Cd2+ damage, ROS formation and catalase disruption whereas chelation of intracellular Fe2+ with desferrioxamine augmented Cd2+ damage, corresponding to hepcidin upregulation. Comparable effects were observed in mCCD(cl.1) cells, indicating equivalent functions of renal hepcidin in different collecting duct segments. In conclusion, hepcidin likely binds Fe2+, but not Cd2+. Because Fe2+ and Cd2+ compete for functional binding sites in proteins, hepcidin affects their free metal ion pools and differentially impacts downstream processes and cell fate.

scholarly journals Roles of TroA and TroR in Metalloregulated Growth and Gene Expression in Treponema denticola

2020 ◽  
Vol 202 (7) ◽  
Author(s):  
Prakaimuk Saraithong ◽  
M. Paula Goetting-Minesky ◽  
Peter M. Durbin ◽  
Spencer W. Olson ◽  
Frank C. Gherardini ◽  
...  
Keyword(s):  
Gene Expression ◽  
Metal Cation ◽  
Metal Homeostasis ◽  
Treponema Denticola ◽  
Content Type ◽  
Host Environment ◽  
Innate Defense ◽  
Cation Uptake ◽  
Iron And Manganese

ABSTRACT The availability of divalent metal cations required as cofactors for microbial metabolism is severely limited in the host environment. Bacteria have evolved highly regulated uptake systems to maintain essential metal homeostasis to meet cellular demands while preventing toxicity. The Tro operon (troABCDR), present in all sequenced Treponema spp., is a member of a highly conserved family of ATP-binding cassette transporters involved in metal cation uptake whose expression is controlled by TroR, a DtxR-like cation-responsive regulatory protein. Transcription of troA responds to divalent manganese and iron (T. denticola) or manganese and zinc (T. pallidum), and metal-dependent TroR binding to the troA promoter represses troA transcription. We report here the construction and complementation of defined T. denticola ΔtroR and ΔtroA strains to characterize (i) the role of TroA in metal-dependent T. denticola growth and (ii) the role of TroR in T. denticola gene expression. We show that TroA expression is required for T. denticola growth under iron- and manganese-limited conditions. Furthermore, TroR is required for the transcriptional regulation of troA in response to iron or manganese, and deletion of troR results in significant differential expression of more than 800 T. denticola genes in addition to troA. These results suggest that (i) TroA-mediated cation uptake is important in metal homeostasis in vitro and may be important for Treponema survival in the host environment and (ii) the absence of TroR results in significant dysregulation of nearly one-third of the T. denticola genome. These effects may be direct (as with troA) or indirect due to dysregulation of metal homeostasis. IMPORTANCE Treponema denticola is one of numerous host-associated spirochetes, a group including commensals, pathobionts, and at least one frank pathogen. While most T. denticola research concerns its role in periodontitis, its relative tractability for growth and genetic manipulation make it a useful model for studying Treponema physiology, metabolism, and host-microbe interactions. Metal micronutrient acquisition and homeostasis are highly regulated both in microbial cells and by host innate defense mechanisms that severely limit metal cation bioavailability. Here, we characterized the T. denticola troABCDR operon, the role of TroA-mediated iron and manganese uptake in growth, and the effects of TroR on global gene expression. This study contributes to our understanding of the mechanisms involved in cellular metal homeostasis required for survival in the host environment.

Customer-centered knowledge management: challenges and implications for knowledge-based innovation in the public transport sector

2015 ◽  
Vol 19 (3) ◽  
pp. 559-578 ◽  
Author(s):  
Stavros Sindakis ◽  
Audrey Depeige ◽  
Eleni Anoyrkati
Keyword(s):  
Knowledge Management ◽  
Public Transport ◽  
Management Practices ◽  
Transport Systems ◽  
Transport Sector ◽  
Content Type ◽  
The Public ◽  
Knowledge Based ◽  
Knowledge Management Practices

Purpose – This study aims to explore the role of knowledge management practices in supporting current and emerging passengers’ and customer needs, aiming to create value. Specifically, the research examines the importance of customer-centred knowledge management in the delivery of innovative services and practices in the public transport sector, promoting the role of interactions between mobility stakeholders and travellers. Design/methodology/approach – A theoretical framework is developed and supported by the background literature on customer-centric knowledge management approaches, business model innovation, as well as on inter-organisational and network co-operations. Findings – Results show that the development of sustainable innovation and technologies in the transport sector requires knowledge management practices, which enable the access to knowledge about users’ needs, the mapping and evaluation of innovative knowledge, the promotion of knowledge-based innovation through collective approaches, as well as the acquisition and integration of new knowledge. Research limitations/implications – The conceptual framework developed in the paper remains limited to a theoretical understanding. Further research should empirically examine knowledge issues related to the intangible character and intellectual capital intensiveness of innovation in the transport sector. Practical implications – Researchers, public transport companies and public transport authorities are expected to benefit from this research, by developing mechanisms for customer-centred knowledge management, which is found to lead to innovative services and practices in the public transport sector. Another practical implication regards the adoption of knowledge management practices, leading to technological innovations in public transport, and advancing the level of sustainability in transport systems. Originality/value – The originality of this study lies in the development of a customer-focussed knowledge management framework, which provides a novel perspective of value creation in an attempt to engage researchers and practitioners from the transport industry in the conceptualisation and development of innovative solutions.

scholarly journals Effects of Oxygen Availability on Acetic Acid Tolerance and Intracellular pH in Dekkera bruxellensis

2016 ◽  
Vol 82 (15) ◽  
pp. 4673-4681 ◽  
Author(s):  
Claudia Capusoni ◽  
Stefania Arioli ◽  
Paolo Zambelli ◽  
M. Moktaduzzaman ◽  
Diego Mora ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Acetic Acid ◽  
Intracellular Ph ◽  
Acid Tolerance ◽  
Oxygen Availability ◽  
Industrial Processes ◽  
Dekkera Bruxellensis ◽  
Acetic Acid Tolerance ◽  
Content Type

ABSTRACTThe yeastDekkera bruxellensis, associated with wine and beer production, has recently received attention, because its high ethanol and acid tolerance enables it to compete withSaccharomyces cerevisiaein distilleries that produce fuel ethanol. We investigated how different cultivation conditions affect the acetic acid tolerance ofD. bruxellensis. We analyzed the ability of two strains (CBS 98 and CBS 4482) exhibiting different degrees of tolerance to grow in the presence of acetic acid under aerobic and oxygen-limited conditions. We found that the concomitant presence of acetic acid and oxygen had a negative effect onD. bruxellensisgrowth. In contrast, incubation under oxygen-limited conditions resulted in reproducible growth kinetics that exhibited a shorter adaptive phase and higher growth rates than those with cultivation under aerobic conditions. This positive effect was more pronounced in CBS 98, the more-sensitive strain. Cultivation of CBS 98 cells under oxygen-limited conditions improved their ability to restore their intracellular pH upon acetic acid exposure and to reduce the oxidative damage to intracellular macromolecules caused by the presence of acetic acid. This study reveals an important role of oxidative stress in acetic acid tolerance inD. bruxellensis, indicating that reduced oxygen availability can protect against the damage caused by the presence of acetic acid. This aspect is important for optimizing industrial processes performed in the presence of acetic acid.IMPORTANCEThis study reveals an important role of oxidative stress in acetic acid tolerance inD. bruxellensis, indicating that reduced oxygen availability can have a protective role against the damage caused by the presence of acetic acid. This aspect is important for the optimization of industrial processes performed in the presence of acetic acid.

The sodium pump in the evolution of animal cells

1995 ◽  
Vol 349 (1329) ◽  
pp. 263-269 ◽  
Keyword(s):  
Sodium Pump ◽  
Transport Systems ◽  
Primary Role ◽  
Bacterial Cells ◽  
Electrochemical Gradient ◽  
Animal Cells ◽  
Osmotic Balance ◽  
Energy Consuming ◽  
P Type

Plant cells and bacterial cells are surrounded by a massive cellulose wall, which constrains their high internal osmotic pressure (tens of atmospheres). Animal cells, in contrast, are in osmotic equilibrium with their environment, have no restraining surround, can take on a variety of shapes and change these from moment to moment. This osmotic balance is achieved by the action of the energy-consuming sodium pump, one of the P-type ATPase transport protein family, members of which are indeed also found in bacteria. The pump’s action brings about a transmembranal electrochemical gradient of sodium ions, harnessed in a range of transport systems that couple the dissipation of this gradient to establishing a gradient of the coupled substrate. The primary role of the sodium pump as a regulator of cell volume has evolved to provide the basis for an enormous variety of physiological functions.

scholarly journals EfaR Is a Major Regulator of Enterococcus faecalis Manganese Transporters and Influences Processes Involved in Host Colonization and Infection

2013 ◽  
Vol 81 (3) ◽  
pp. 935-944 ◽  
Author(s):  
M. C. Abrantes ◽  
J. Kok ◽  
M. de F. Lopes
Keyword(s):  
Oxidative Stress ◽  
Metal Ions ◽  
Enterococcus Faecalis ◽  
Bacterial Endocarditis ◽  
Nosocomial Pathogen ◽  
Host Colonization ◽  
Content Type ◽  
Bacterial Pathogenicity

ABSTRACTMetal ions, in particular manganese, are important modulators of bacterial pathogenicity. However, little is known about the role of manganese-dependent proteins in the nosocomial pathogenEnterococcus faecalis, a major cause of bacterial endocarditis. The present study demonstrates that the DtxR/MntR family metalloregulator EfaR ofE. faecaliscontrols the expression of several of its regulon members in a manganese-dependent way. We also show thatefaRinactivation impairs the ability ofE. faecalisto form biofilms, to survive inside macrophages, and to tolerate oxidative stress. Our results reveal that EfaR is an important modulator ofE. faecalisvirulence and link manganese homeostasis to enterococcal pathogenicity.

scholarly journals BaeSR, Involved in Envelope Stress Response, Protects against Lysogenic Conversion by Shiga Toxin 2-Encoding Phages

2015 ◽  
Vol 83 (4) ◽  
pp. 1451-1457 ◽  
Author(s):  
Lejla Imamovic ◽  
Alexandre Martínez-Castillo ◽  
Carmen Benavides ◽  
Maite Muniesa
Keyword(s):  
Stress Responses ◽  
Shiga Toxin ◽  
Phage Infection ◽  
Bacterial Cells ◽  
Content Type ◽  
Signaling Systems ◽  
E Coli ◽  
Envelope Stress ◽  
Lysogenic Conversion

Infection and lysogenic conversion with Shiga toxin-encoding bacteriophages (Stx phages) drive the emergence of new Shiga toxin-producingEscherichia colistrains. Phage attachment to the bacterial surface is the first stage of phage infection. Envelope perturbation causes activation of envelope stress responses in bacterial cells. Although many external factors are known to activate envelope stress responses, the role of these responses in the phage-bacterium interaction remains unexplored. Here, we investigate the link between three envelope signaling systems inE. coli(RcsBC, CpxAR, and BaeSR) and Stx2 phage infection by determining the success of bacterial lysogenic conversion. For this purpose,E. coliDH5α wild-type (WT) and mutant strains lacking RcsBC, CpxAR, or BaeSR signaling systems were incubated with a recombinant Stx2 phage (933W). Notably, the number of lysogens obtained with the BaeSR mutant was 5 log10units higher than with the WT, and the same differences were observed when using 7 different Stx2 phages. To assess whether the membrane receptor used by Stx phages, BamA, was involved in the differences observed,bamAgene expression was monitored by reverse transcription-quantitative PCR (RT-qPCR) in all host strains. A 4-fold-higherbamAexpression level was observed in the BaeSR mutant than in the WT strain, suggesting that differential expression of the receptor used by Stx phages accounted for the increase in the number of lysogenization events. Establishing the link between the role of stress responses and phage infection has important implications for understanding the factors affecting lysogenic conversion, which drives the emergence of new pathogenic clones.

scholarly journals Manganese Homeostasis in Group A Streptococcus Is Critical for Resistance to Oxidative Stress and Virulence

mBio ◽  
2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Andrew G. Turner ◽  
Cheryl-lynn Y. Ong ◽  
Christine M. Gillen ◽  
Mark R. Davies ◽  
Nicholas P. West ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Peroxide ◽  
Transition Metal ◽  
Metal Ion ◽  
Double Mutant ◽  
Efflux Pump ◽  
Group A Streptococcus ◽  
Wild Type ◽  
Group A

ABSTRACT Streptococcus pyogenes (group A Streptococcus [GAS]) is an obligate human pathogen responsible for a spectrum of human disease states. Metallobiology of human pathogens is revealing the fundamental role of metals in both nutritional immunity leading to pathogen starvation and metal poisoning of pathogens by innate immune cells. Spy0980 (MntE) is a paralog of the GAS zinc efflux pump CzcD. Through use of an isogenic mntE deletion mutant in the GAS serotype M1T1 strain 5448, we have elucidated that MntE is a manganese-specific efflux pump required for GAS virulence. The 5448ΔmntE mutant had significantly lower survival following infection of human neutrophils than did the 5448 wild type and the complemented mutant (5448ΔmntE::mntE). Manganese homeostasis may provide protection against oxidative stress, explaining the observed ex vivo reduction in virulence. In the presence of manganese and hydrogen peroxide, 5448ΔmntE mutant exhibits significantly lower survival than wild-type 5448 and the complemented mutant. We hypothesize that MntE, by maintaining homeostatic control of cytoplasmic manganese, ensures that the peroxide response repressor PerR is optimally poised to respond to hydrogen peroxide stress. Creation of a 5448ΔmntE-ΔperR double mutant rescued the oxidative stress resistance of the double mutant to wild-type levels in the presence of manganese and hydrogen peroxide. This work elucidates the mechanism for manganese toxicity within GAS and the crucial role of manganese homeostasis in maintaining GAS virulence. IMPORTANCE Manganese is traditionally viewed as a beneficial metal ion to bacteria, and it is also established that most bacteria can tolerate high concentrations of this transition metal. In this work, we show that in group A Streptococcus, mutation of the mntE locus, which encodes a transport protein of the cation diffusion facilitator (CDF) family, results in accumulation of manganese and sensitivity to this transition metal ion. The toxicity of manganese is indirect and is the result of a failure of the PerR regulator to respond to oxidative stress in the presence of high intracellular manganese concentrations. These results highlight the importance of MntE in manganese homeostasis and maintenance of an optimal manganese/iron ratio in GAS and the impact of manganese on resistance to oxidative stress and virulence.

Sign in / Sign up

Export Citation Format

Share Document