AguR, a Transmembrane Transcription Activator of the Putrescine Biosynthesis Operon in Lactococcus lactis, Acts in Response to the Agmatine Concentration

ABSTRACTDairy industry fermentative processes mostly useLactococcus lactisas a starter. However, some dairyL. lactisstrains produce putrescine, a biogenic amine that raises food safety and spoilage concerns, via the agmatine deiminase (AGDI) pathway. The enzymatic activities responsible for putrescine biosynthesis in this bacterium are encoded by the AGDI gene cluster. The role of the catabolic genesaguB,aguD,aguA, andaguChas been studied, but knowledge regarding the role ofaguR(the first gene in the cluster) remains limited. In the present work,aguRwas found to be a very low level constitutively expressed gene that is essential for putrescine biosynthesis and is transcribed independently of the polycistronic mRNA encoding the catabolic genes (aguBDAC). In response to agmatine, AguR acts as a transcriptional activator of theaguBpromoter (PaguB), which drives the transcription of theaguBDACoperon. Inverted sequences required for PaguBactivity were identified by deletion analysis. Further work indicated that AguR is a transmembrane protein which might function as a one-component signal transduction system that senses the agmatine concentration of the medium and, accordingly, regulates the transcription of theaguBDACoperon through a C-terminal cytoplasmic DNA-binding domain typically found in LuxR-like proteins.

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Two different activities of Suppressor of Hairless during wing development in Drosophila

Development ◽

10.1242/dev.127.16.3553 ◽

2000 ◽

Vol 127 (16) ◽

pp. 3553-3566 ◽

Cited By ~ 3

Author(s):

T. Klein ◽

L. Seugnet ◽

M. Haenlin ◽

A. Martinez Arias

Keyword(s):

Target Genes ◽

Transmembrane Protein ◽

Current Model ◽

Notch Pathway ◽

Notch Signalling ◽

Wing Development ◽

Transcription Activator ◽

Cell Fates ◽

H Protein

The Notch pathway plays a crucial and universal role in the assignation of cell fates during development. In Drosophila, Notch is a transmembrane protein that acts as a receptor of two ligands Serrate and delta. The current model of Notch signal transduction proposes that Notch is activated upon binding its ligands and that this leads to the cleavage and release of its intracellular domain (also called Nintra). Nintra translocates to the nucleus where it forms a dimeric transcription activator with the Su(H) protein. In contrast with this activation model, experiments with the vertebrate homologue of Su(H), CBF1, suggest that, in vertebrates, Nintra converts CBF1 from a repressor into an activator. Here we have assessed the role of Su(H) in Notch signalling during the development of the wing of Drosophila. Our results show that, during this process, Su(H) can activate the expression of some Notch target genes and that it can do so without the activation of the Notch pathway or the presence of Nintra. In contrast, the activation of other Notch target genes requires both Su(H) and Nintra, and, in the absence of Nintra, Su(H) acts as a repressor. We also find that the Hairless protein interacts with Notch signalling during wing development and inhibits the activity of Su(H). Our results suggest that, in Drosophila, the activation of Su(H) by Notch involve the release of Su(H) from an inhibitory complex, which contains the Hairless protein. After its release Su(H) can activate gene expression in absence of Nintra.

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Mechanism of Attenuation of Uranyl Toxicity by Glutathione in Lactococcus lactis

Applied and Environmental Microbiology ◽

10.1128/aem.00538-16 ◽

2016 ◽

Vol 82 (12) ◽

pp. 3563-3571 ◽

Cited By ~ 6

Author(s):

Muhammad H. Obeid ◽

Jana Oertel ◽

Marc Solioz ◽

Karim Fahmy

Keyword(s):

Heavy Metals ◽

Lactococcus Lactis ◽

Metal Toxicity ◽

Molecular Mechanisms ◽

Model Organism ◽

Cell Number ◽

Metal Resistance ◽

Titration Calorimetry ◽

Content Type

ABSTRACTBoth prokaryotic and eukaryotic organisms possess mechanisms for the detoxification of heavy metals, and these mechanisms are found among distantly related species. We investigated the role of intracellular glutathione (GSH), which, in a large number of taxa, plays a role in protection against the toxicity of common heavy metals. Anaerobically grownLactococcus lactiscontaining an inducible GSH synthesis pathway was used as a model organism. Its physiological condition allowed study of putative GSH-dependent uranyl detoxification mechanisms without interference from additional reactive oxygen species. By microcalorimetric measurements of metabolic heat during cultivation, it was shown that intracellular GSH attenuates the toxicity of uranium at a concentration in the range of 10 to 150 μM. In this concentration range, no effect was observed with copper, which was used as a reference for redox metal toxicity. At higher copper concentrations, GSH aggravated metal toxicity. Isothermal titration calorimetry revealed the endothermic binding of U(VI) to the carboxyl group(s) of GSH rather than to the reducing thiol group involved in copper interactions. The data indicate that the primary detoxifying mechanism is the intracellular sequestration of carboxyl-coordinated U(VI) into an insoluble complex with GSH. The opposite effects on uranyl and on copper toxicity can be related to the difference in coordination chemistry of the respective metal-GSH complexes, which cause distinct growth phase-specific effects on enzyme-metal interactions.IMPORTANCEUnderstanding microbial metal resistance is of particular importance for bioremediation, where microorganisms are employed for the removal of heavy metals from the environment. This strategy is increasingly being considered for uranium. However, little is known about the molecular mechanisms of uranyl detoxification. Existing studies of different taxa show little systematics but hint at a role of glutathione (GSH). Previous work could not unequivocally demonstrate a GSH function in decreasing the presumed uranyl-induced oxidative stress, nor could a redox-independent detoxifying action of GSH be identified. Combining metabolic calorimetry with cell number-based assays and genetics analysis enables a novel and general approach to quantify toxicity and relate it to molecular mechanisms. The results show that GSH-expressing microorganisms appear advantageous for uranyl bioremediation.

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Poles Apart: Where and How Cells Construct Nisin

mBio ◽

10.1128/mbio.02991-20 ◽

2020 ◽

Vol 11 (6) ◽

pp. e02991-20

Author(s):

Colin Hill

Keyword(s):

Amino Acid ◽

Lactococcus Lactis ◽

Spatial Organization ◽

Food Preservative ◽

Content Type ◽

Link Type ◽

Biosynthetic Machinery

ABSTRACTNisin is a 34-amino-acid lantibiotic that has been used commercially for almost a century as a food preservative. In order to produce active nisin, Lactococcus lactis requires an 11-gene operon that encodes proteins involved in modification, processing, transport, immunity, and regulation. While the role of each of the 11 proteins is well understood, the location and spatial organization of the biosynthetic machinery that involves NisA, NisB, NisC, NisT, and NisP remain to be determined. In this elegant paper (J. Chen, A. J. van Heel, and O. P. Kuipers, mBio 11:e02825-20, 2020, https://doi.org/10.1128/mBio.02825-20), we learn that a NisB dimer is recruited to the “old” pole of a dividing cell, where it assembles with NisC to form a modification complex that can engage with NisA. Unexpectedly, the NisT transporter does not stably assemble into this complex but is distributed around the membrane until it engages with the NisABC complex to transport NisA across the membrane, whereupon it dissociates from NisBC.

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Uptake of α-Ketoglutarate by Citrate Transporter CitP Drives Transamination in Lactococcus lactis

Applied and Environmental Microbiology ◽

10.1128/aem.02254-12 ◽

2012 ◽

Vol 79 (4) ◽

pp. 1095-1101 ◽

Cited By ~ 13

Author(s):

Agata M. Pudlik ◽

Juke S. Lolkema

Keyword(s):

Amino Acids ◽

Lactococcus Lactis ◽

Expression System ◽

Ph Profile ◽

Content Type ◽

Citrate Transporter ◽

Keto Acids ◽

Branched Chain ◽

Mode Of Transport

ABSTRACTTransamination is the first step in the conversion of amino acids into aroma compounds by lactic acid bacteria (LAB) used in food fermentations. The process is limited by the availability of α-ketoglutarate, which is the best α-keto donor for transaminases in LAB. Here, uptake of α-ketoglutarate by the citrate transporter CitP is reported. Cells ofLactococcus lactisIL1403 expressing CitP showed significant levels of transamination activity in the presence of α-ketoglutarate and one of the amino acids Ile, Leu, Val, Phe, or Met, while the same cells lacking CitP showed transamination activity only after permeabilization of the cell membrane. Moreover, the transamination activity of the cells followed the levels of CitP in a controlled expression system. The involvement of CitP in the uptake of the α-keto donor was further demonstrated by the increased consumption rate in the presence ofl-lactate, which drives CitP in the fast exchange mode of transport. Transamination is the only active pathway for the conversion of α-ketoglutarate in IL1403; a stoichiometric conversion to glutamate and the corresponding α-keto acid from the amino acids was observed. The transamination activity by both the cells and the cytoplasmic fraction showed a remarkably flat pH profile over the range from pH 5 to pH 8, especially with the branched-chain amino acids. Further metabolism of the produced α-keto acids into α-hydroxy acids and other flavor compounds required the coupling of transamination to glycolysis. The results suggest a much broader role of the citrate transporter CitP in LAB than citrate uptake in the citrate fermentation pathway alone.

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Enterococcus faecalis Manganese Exporter MntE Alleviates Manganese Toxicity and Is Required for Mouse Gastrointestinal Colonization

Infection and Immunity ◽

10.1128/iai.00058-20 ◽

2020 ◽

Vol 88 (6) ◽

Cited By ~ 1

Author(s):

Ling Ning Lam ◽

Jun Jie Wong ◽

Kelvin Kian Long Chong ◽

Kimberly A. Kline

Keyword(s):

Enterococcus Faecalis ◽

Gi Tract ◽

Biofilm Growth ◽

Mn Toxicity ◽

Content Type ◽

Excess Iron ◽

Catabolic Genes ◽

Gastrointestinal Colonization ◽

Excess Fe

ABSTRACT Bacterial pathogens encounter a variety of nutritional environments in the human host, including nutrient metal restriction and overload. Uptake of manganese (Mn) is essential for Enterococcus faecalis growth and virulence; however, it is not known how this organism prevents Mn toxicity. In this study, we examine the role of the highly conserved MntE transporter in E. faecalis Mn homeostasis and virulence. We show that inactivation of mntE results in growth restriction in the presence of excess Mn, but not other metals, demonstrating its specific role in Mn detoxification. Upon growth in the presence of excess Mn, an mntE mutant accumulates intracellular Mn, iron (Fe), and magnesium (Mg), supporting a role for MntE in Mn and Fe export and a role for Mg in offsetting Mn toxicity. Growth of the mntE mutant in excess Fe also results in increased levels of intracellular Fe, but not Mn or Mg, providing further support for MntE in Fe efflux. Inactivation of mntE in the presence of excess iron also results in the upregulation of glycerol catabolic genes and enhanced biofilm growth, and addition of glycerol is sufficient to augment biofilm growth for both the mntE mutant and its wild-type parental strain, demonstrating that glycerol availability significantly enhances biofilm formation. Finally, we show that mntE contributes to colonization of the antibiotic-treated mouse gastrointestinal (GI) tract, suggesting that E. faecalis encounters excess Mn in this niche. Collectively, these findings demonstrate that the manganese exporter MntE plays a crucial role in E. faecalis metal homeostasis and virulence.

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Role of Fig1, a Component of the Low-Affinity Calcium Uptake System, in Growth and Sexual Development of Filamentous Fungi

Eukaryotic Cell ◽

10.1128/ec.00007-12 ◽

2012 ◽

Vol 11 (8) ◽

pp. 978-988 ◽

Cited By ~ 28

Author(s):

Brad Cavinder ◽

Frances Trail

Keyword(s):

Mating Type ◽

Sexual Development ◽

Calcium Uptake ◽

Transmembrane Protein ◽

Uptake System ◽

Fruiting Bodies ◽

Wild Type ◽

Content Type ◽

High Affinity

ABSTRACT The function of Fig1, a transmembrane protein of the low-affinity calcium uptake system (LACS) in fungi, was examined for its role in the growth and development of the plant pathogen Fusarium graminearum . The Δ fig1 mutants failed to produce mature perithecia, and sexual development was halted prior to the formation of perithecium initials. The loss of Fig1 function also resulted in a reduced vegetative growth rate. Macroconidium production was reduced 70-fold in the Δ fig1 mutants compared to the wild type. The function of the high-affinity calcium uptake system (HACS), comprised of the Ca 2+ channels Mid1 and Cch1, was previously characterized for F. graminearum . To better understand the roles of the LACS and the HACS, Δ fig1 Δ mid1 , Δ fig1 Δ cch1 , and Δ fig1 Δ mid1 Δ cch1 double and triple mutants were generated, and the phenotypes of these mutants were more severe than those of the Δ fig1 mutants. Pathogenicity on wheat was unaffected for the Δ fig1 mutants, but the Δ fig1 Δ mid1 , Δ fig1 Δ cch1 , and Δ fig1 Δ mid1 Δ cch1 mutants, lacking both LACS and HACS functions, had reduced pathogenicity. Additionally, Δ fig1 mutants of Neurospora crassa were examined and did not affect filamentous growth or female fertility in a Δ fig1 mating type A strain, but the Δ fig1 mating type a strain failed to produce fertile fruiting bodies. These results are the first report of Fig1 function in filamentous ascomycetes and expand its role to include complex fruiting body and ascus development.

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Long-term management of patients with multiple brain metastases after shaped beam radiosurgery

Journal of Neurosurgery ◽

10.3171/jns.2004.101.supplement_3.0406 ◽

2004 ◽

pp. 406-412

Author(s):

Paul Okunieff ◽

Michael C. Schell ◽

Russell Ruo ◽

E. Ronald Hale ◽

Walter G. O'Dell ◽

...

Keyword(s):

Brain Metastases ◽

Tumor Control ◽

Content Type ◽

Negative Results ◽

Multiple Metastases ◽

Extracranial Disease ◽

Successful Control ◽

The Brain

✓ The role of radiosurgery in the treatment of patients with advanced-stage metastatic disease is currently under debate. Previous randomized studies have not consistently supported the use of radiosurgery to treat patients with numbers of brain metastases. In negative-results studies, however, intracranial tumor control was high but extracranial disease progressed; thus, patient survival was not greatly affected, although neurocognitive function was generally maintained until death. Because the future promises improved systemic (extracranial) therapy, the successful control of brain disease is that much more crucial. Thus, for selected patients with multiple metastases to the brain who remain in good neurological condition, aggressive lesion-targeting radiosurgery should be very useful. Although a major limitation to success of this therapy is the lack of control of extracranial disease in most patients, it is clear that well-designed, aggressive treatment substantially decreases the progression of brain metastases and also improves neurocognitive survival. The authors present the management and a methodology for rational treatment of a patient with breast cancer who has harbored 24 brain metastases during a 3-year period.

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Vulnerable adults in police custody

The Journal of Adult Protection ◽

10.1108/jap-09-2019-0031 ◽

2019 ◽

Vol 22 (1) ◽

pp. 5-8

Author(s):

Ian Cummins

Keyword(s):

Design Methodology ◽

Research Literature ◽

Police Custody ◽

England And Wales ◽

Content Type ◽

Increased Risk ◽

Vulnerable Adults

Purpose The purpose of this paper is to discuss the recent National Appropriate Adult Network (NAAN) report on the role of the appropriate adult. Design/methodology/approach This paper is based on the NAAN report and a review of relevant policy and research literature. Findings There to Help 2 highlights that there are still significant gaps in the provision of appropriate adult schemes across England and Wales. These gaps potentially place vulnerable adults at increased risk. Originality/value This paper is a review of recent research.

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Financial access and economic development: the moderating role of financial consumer protection

International Journal of Managerial Finance ◽

10.1108/ijmf-05-2018-0132 ◽

2019 ◽

Vol 15 (4) ◽

pp. 406-424 ◽

Cited By ~ 2

Author(s):

Maryam Kriese ◽

Joshua Yindenaba Abor ◽

Elikplimi Agbloyor

Keyword(s):

Economic Development ◽

World Bank ◽

Financial Literacy ◽

Compliance Monitoring ◽

Financial Access ◽

Policy Makers ◽

Content Type ◽

The World Bank ◽

Moderating Role

Purpose The purpose of this paper is to examine the moderating role of financial consumer protection (FCP) in the access–development nexus. Design/methodology/approach The study is based on cross-country data on 102 countries surveyed in the World Bank Global Survey on FCP and Financial Literacy (2013). The White heteroscedasticity adjusted regressions and Two-stage least squares regressions (2SLS) are used for the estimation. Findings Interactions between FCP regulations that foster fair treatment, disclosure, dispute resolution and recourse and financial access have positive net effects on economic development. However, there is no sufficient evidence to suggest that interactions between financial access and enforcement and compliance monitoring regulations have a significant effect on economic development. Practical implications First, policy makers should continue with efforts aimed at instituting FCP regimes as part of strategies aimed at broadening access to financial services for enhanced economic development. Second, instituting FCP regimes per se may not be enough. Policy makers need to consider possible intervening factors such as the provision of adequate resources and supervisory authority, for compliance monitoring and enforcement to achieve the expected positive effect on economic development. Originality/value This study extends evidence in the law–finance–growth literature by providing empirical evidence on the effect of legal institution specific to the protection of retail financial consumers on the access–development nexus using a nouvel data set, the World Bank Global survey on FCP and Financial Literacy (2013).

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Categorization flexibility and unconventional choices: is life an adventure?

European Journal of Marketing ◽

10.1108/ejm-10-2018-0663 ◽

2020 ◽

Vol 54 (8) ◽

pp. 1963-1986

Author(s):

Tilottama G. Chowdhury ◽

Feisal Murshed

Keyword(s):

Interactive Effect ◽

Interactive Effects ◽

Cognitive Capacity ◽

Purchase Behavior ◽

Consumer Decision Making ◽

Cross Sectional ◽

Content Type ◽

Cross Domain ◽

Multiple Domains

Purpose This paper proposes that categorization flexibility, operationalized as the cognitive capacity that cross-categorizes products in multiple situational categories across multiple domains, might favorably influence a consumer’s evaluation of unconventional options. Design/methodology/approach Experimental research design is used to test the theory. An exploratory study first establishes the effect of categorization flexibility in a non-food domain. Study 1 documents the moderating role of decision domain, showing that the effect works only under low- (vs high-) consequence domain. Studies 2A and 2B further refine the notion by showing that individuals can be primed in a relatively higher categorization flexibility frame of mind. Study 3 demonstrates the interactive effect of categorization flexibility and adventure priming in a high-consequence domain. Study 4 integrates the interactive effects of decisions with low- vs high-consequence, adventure priming and categorization flexibility within a single decision domain of high consequence. Findings Consumers with higher- (vs lower-) categorization flexibility tend to opt for unconventional choices when the decision domain entails low consequences, whereas such a result does not hold under decision domain of high consequences. The categorization flexibility effects in case of low-consequence decision domain holds true even when consumers are primed to be categorization flexible. Furthermore, with additional adventure priming, consumers show an increased preference for unconventional options even under a decision domain with high consequence. Research limitations/implications This study could not examine real purchase behavior as results are based on cross-sectional, behavioral intention data. In addition, it did not examine the underlying reason for presence of cross-domain categorization flexibility index. Practical implications The results suggest that stimuli may be tailored to consumers in ways that increase the salience and the perceived attractiveness of unconventional choices. Further, data reinforce the notion of cross-categorical interrelations among different domains, which could be leveraged by marketers. Originality/value This study represents the first documentation of the potential ways by which unconventional product choice might be a function of individuals’ categorization flexibility level across different types of decision domains. The findings yield implications that are novel to both categorization and consumer decision-making literature.

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