scholarly journals Selective Utilization of Exogenous Amino Acids by Dehalococcoides ethenogenes Strain 195 and Its Effects on Growth and Dechlorination Activity

2011 ◽  
Vol 77 (21) ◽  
pp. 7797-7803 ◽  
Author(s):  
Wei-Qin Zhuang ◽  
Shan Yi ◽  
Xueyang Feng ◽  
Stephen H. Zinder ◽  
Yinjie J. Tang ◽  
...  
Keyword(s):  
Amino Acids ◽  
De Novo ◽  
Growth Stages ◽  
Amino Acid Transporters ◽  
Isoleucine Leucine ◽  
Content Type ◽  
Nutritional Conditions ◽  
Dehalococcoides Ethenogenes ◽  
Casamino Acids ◽  
Slow Growing

ABSTRACTBacteria of the genusDehalococcoidesare important members of bioremediation communities because of their ability to detoxify chloroethenes to the benign end product ethene. Genome-enabled studies conducted withDehalococcoides ethenogenes195 have revealed that two ATP-binding cassette (ABC)-type amino acid transporters are expressed during its exponential growth stages. In light of previous findings that Casamino Acids enhanced its dechlorination activity, we hypothesized that strain 195 is capable of importing amino acids from its environment to facilitate dechlorination and growth. To test this hypothesis, we applied isotopomer-based dilution analysis with13C-labeled acetate to differentiate the amino acids that were taken up by strain 195 from those synthesizedde novoand to determine the physiological changes caused by the significantly incorporated amino acids. Our results showed that glutamate/glutamine and aspartate/asparagine were almost exclusively synthesized by strain 195, even when provided in excess in the medium. In contrast, phenylalanine, isoleucine, leucine, and methionine were identified as the four most highly incorporated amino acids, at levels >30% of respective proteinogenic amino acids. When either phenylalanine or all four highly incorporated amino acids were added to the defined mineral medium, the growth rates, dechlorination activities, and yields of strain 195 were enhanced to levels similar to those observed with supplementation with 20 amino acids. However, genes for the putative ABC-type amino acids transporters and phenylalanine biosynthesis exhibited insignificant regulation in response to the imported amino acids. This study also demonstrates that using isotopomer-based metabolite analysis can be an efficient strategy for optimizing nutritional conditions for slow-growing microorganisms.

scholarly journals Regulation of Amino Acid Transport in Saccharomyces cerevisiae

2019 ◽  
Vol 83 (4) ◽  
Author(s):  
Frans Bianchi ◽  
Joury S. van’t Klooster ◽  
Stephanie J. Ruiz ◽  
Bert Poolman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Amino Acid ◽  
De Novo ◽  
Amino Acid Transporters ◽  
Content Type ◽  
Growth And Survival ◽  
Amino Acid Homeostasis ◽  
Underlying Mechanisms ◽  
Amino Acid Sensing

SUMMARY We review the mechanisms responsible for amino acid homeostasis in Saccharomyces cerevisiae and other fungi. Amino acid homeostasis is essential for cell growth and survival. Hence, the de novo synthesis reactions, metabolic conversions, and transport of amino acids are tightly regulated. Regulation varies from nitrogen pool sensing to control by individual amino acids and takes place at the gene (transcription), protein (posttranslational modification and allostery), and vesicle (trafficking and endocytosis) levels. The pools of amino acids are controlled via import, export, and compartmentalization. In yeast, the majority of the amino acid transporters belong to the APC (amino acid-polyamine-organocation) superfamily, and the proteins couple the uphill transport of amino acids to the electrochemical proton gradient. Although high-resolution structures of yeast amino acid transporters are not available, homology models have been successfully exploited to determine and engineer the catalytic and regulatory functions of the proteins. This has led to a further understanding of the underlying mechanisms of amino acid sensing and subsequent downregulation of transport. Advances in optical microscopy have revealed a new level of regulation of yeast amino acid transporters, which involves membrane domain partitioning. The significance and the interrelationships of the latest discoveries on amino acid homeostasis are put in context.

scholarly journals Basal-Level Effects of (p)ppGpp in the Absence of Branched-Chain Amino Acids in Actinobacillus pleuropneumoniae

2020 ◽  
Vol 202 (8) ◽  
Author(s):  
Gang Li ◽  
Qian Zhao ◽  
Tian Luan ◽  
Yangbo Hu ◽  
Yueling Zhang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
De Novo ◽  
Model Organism ◽  
Stringent Response ◽  
Actinobacillus Pleuropneumoniae ◽  
Branched Chain Amino Acids ◽  
Content Type ◽  
Phenotypic Differences ◽  
Branched Chain

ABSTRACT The (p)ppGpp-mediated stringent response (SR) is a highly conserved regulatory mechanism in bacterial pathogens, enabling adaptation to adverse environments, and is linked to pathogenesis. Actinobacillus pleuropneumoniae can cause damage to the lungs of pigs, its only known natural host. Pig lungs are known to have a low concentration of free branched-chain amino acids (BCAAs) compared to the level in plasma. We had investigated the role for (p)ppGpp in viability and biofilm formation of A. pleuropneumoniae. Now, we sought to determine whether (p)ppGpp was a trigger signal for the SR in A. pleuropneumoniae in the absence of BCAAs. Combining transcriptome and phenotypic analyses of the wild type (WT) and an relA spoT double mutant [which does not produce (p)ppGpp], we found that (p)ppGpp could repress de novo purine biosynthesis and activate antioxidant pathways. There was a positive correlation between GTP and endogenous hydrogen peroxide content. Furthermore, the growth, viability, morphology, and virulence were altered by the inability to produce (p)ppGpp. Genes involved in the biosynthesis of BCAAs were constitutively upregulated, regardless of the existence of BCAAs, without accumulation of (p)ppGpp beyond a basal level. Collectively, our study shows that the absence of BCAAs was not a sufficient signal to trigger the SR in A. pleuropneumoniae. (p)ppGpp-mediated regulation in A. pleuropneumoniae is different from that described for the model organism Escherichia coli. Further work will establish whether the (p)ppGpp-dependent SR mechanism in A. pleuropneumoniae is conserved among other veterinary pathogens, especially those in the Pasteurellaceae family. IMPORTANCE (p)ppGpp is a key player in reprogramming transcriptomes to respond to nutritional challenges. Here, we present transcriptional and phenotypic differences of A. pleuropneumoniae grown in different chemically defined media in the absence of (p)ppGpp. We show that the deprivation of branched-chain amino acids (BCAAs) does not elicit a change in the basal-level (p)ppGpp, but this level is sufficient to regulate the expression of BCAA biosynthesis. The mechanism found in A. pleuropneumoniae is different from that of the model organism Escherichia coli but similar to that found in some Gram-positive bacteria. This study not only broadens the research scope of (p)ppGpp but also further validates the complexity and multiplicity of (p)ppGpp regulation in microorganisms that occupy different biological niches.

scholarly journals Lysine and Threonine Biosynthesis from Aspartate Contributes to Staphylococcus aureus Growth in Calf Serum

2016 ◽  
Vol 82 (20) ◽  
pp. 6150-6157 ◽  
Author(s):  
Yuichi Oogai ◽  
Masaya Yamaguchi ◽  
Miki Kawada-Matsuo ◽  
Tomoko Sumitomo ◽  
Shigetada Kawabata ◽  
...  
Keyword(s):  
Amino Acids ◽  
Staphylococcus Aureus ◽  
Bacterial Growth ◽  
De Novo ◽  
Calf Serum ◽  
Mouse Serum ◽  
Lower Growth ◽  
Content Type ◽  
Semialdehyde Dehydrogenase ◽  
Threonine Biosynthesis

ABSTRACTStaphylococcus aureusis a human pathogen, andS. aureusbacteremia can cause serious problems in humans. To identify the genes required for bacterial growth in calf serum (CS), a library ofS. aureusmutants with randomly inserted transposons were analyzed for growth in CS, and the aspartate semialdehyde dehydrogenase (asd)-inactivated mutant exhibited significantly reduced growth in CS compared with the wild type (WT). The mutant also exhibited significantly reduced growth in medium, mimicking the concentrations of amino acids and glucose in CS. Asd is an essential enzyme for the biosynthesis of lysine, methionine, and threonine from aspartate. We constructed inactivated mutants of the genes for lysine (lysA), methionine (metE), and threonine (thrC) biosynthesis and found that the inactivated mutants oflysAandthrCexhibited significantly lower growth in CS than the WT, but the growth of themetEmutant was similar to that of the WT. The reduced growth of theasdmutant was recovered by addition of 100 μg/ml lysine and threonine in CS. These results suggest thatS. aureusrequires lysine and threonine biosynthesis to grow in CS. On the other hand, theasd-,lysA-,metE-, andthrC-inactivated mutants exhibited significantly reduced growth in mouse serum compared with the WT. In mouse bacteremia experiments, theasd-,lysA-,metE-, andthrC-inactivated mutants exhibited attenuated virulence compared with WT infection. In conclusion, our results suggest that the biosynthesis ofde novoaspartate family amino acids, especially lysine and threonine, is important for staphylococcal bloodstream infection.IMPORTANCEStudying the growth of bacteria in blood is important for understanding its pathogenicity in the host.Staphylococcus aureussometimes causes bacteremia or sepsis. However, the factors responsible forS. aureusgrowth in the blood are not well understood. In this study, using a library of 2,914 transposon-insertional mutants in theS. aureusMW2 strain, we identified the factors responsible for bacterial growth in CS. We found that inactivation of the lysine and threonine biosynthesis genes led to deficient growth in CS. However, the inactivation of these genes did not affectS. aureusgrowth in general medium. Because the concentration of amino acids in CS is low compared to that in general bacterial medium, our results suggest that lysine and threonine biosynthesis is important for the growth ofS. aureusin CS. Our findings provide new insights forS. aureusadaptation in the host and for understanding the pathogenesis of bacteremia.

scholarly journals Dynamic and migration characteristics of soil free amino acids during the whole growth period of rice after application of milk vetch

2021 ◽  
Author(s):  
Jing Yang ◽  
Yi Lin ◽  
Christopher Rensing ◽  
Liming Zhang ◽  
Biqing Zhou ◽  
...  
Keyword(s):  
Amino Acids ◽  
Free Amino Acids ◽  
Free Amino ◽  
Bacterial Biomass ◽  
Growth Period ◽  
Inhibitory Effect ◽  
Growth Stages ◽  
Isoleucine Leucine ◽  
Total Contribution ◽  
And Migration

Abstract. Free amino acids (FAAs) in soil play an important role in the soil nitrogen cycle and plant nutrition. However, the attributing factors and migration characteristics of free amino acid pools in paddy soils after green manure application during the entire growth period of rice have not been elucidated. In this study, a single application of chemical fertilizer (CK) was used as a control under equal nitrogen, phosphorus and potassium conditions, and different application rates of milk vetch (15 000 kghm−2(CL), 30 000 kghm−2(CM) and 45 000 kg hm−2(CH)) were selected to investigate the dynamic of FAAs concentration and composition in paddy soil. Soil FAAs concentration at different growth stages under the same fertilization treatments was highest at the seedling stage and lowest at the tillering stage. The concentration of threonine, alanine, valine, isoleucine, leucine, phenylalanine was most abundant under different fertilization treatments during the growth period, accounting for 59.42 %–76.46 % of the respective FAAs pool. The application of milk vetch was shown to increase the soil FAAs concentration, especially glutamic acid, which increased by 368.17 %–680.78 %, but excessive application had an inhibitory effect. Soil pH, organic matter, protease, bacterial biomass and community were critical factors affecting the concentration of soil FAAs. Bacteroidetes, Firmicutes and Nitrospirae significantly affected the dynamics of FAAs in bacterial communities, and their total contribution rate was 56.89 %. FAAs displayed significant vertical profile characteristics, and the mobility of serine, glycine and proline was high. Conclusively, the application of milk vetch was able to significantly change the concentration and composition of soil FAAs, which may affect the capture of N by plants.

scholarly journals Broad-Spectrum Amino Acid Transporters ClAAP3 and ClAAP6 Expressed in Watermelon Fruits

2019 ◽  
Vol 20 (23) ◽  
pp. 5855 ◽  
Author(s):  
Tianran Shi ◽  
Vijay Joshi ◽  
Madhumita Joshi ◽  
Stanislav Vitha ◽  
Holly Gibbs ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Broad Spectrum ◽  
De Novo ◽  
Early Stage ◽  
Expression Profiles ◽  
Functional Characterization ◽  
Gene Expression Profiles ◽  
Amino Acid Transporters ◽  
Amino Acid Permease

Watermelon fruit contains a high percentage of amino acid citrulline (Cit) and arginine (Arg). Cit and Arg accumulation in watermelon fruit are most likely mediated by both de novo synthesis from other amino acids within fruits and direct import from source tissues (leaves) through the phloem. The amino acid transporters involved in the import of Cit, Arg, and their precursors into developing fruits of watermelon have not been reported. In this study, we have compiled the list of putative amino acid transporters in watermelon and characterized transporters that are expressed in the early stage of fruit development. Using the yeast complementation study, we characterized ClAAP3 (Cla023187) and ClAAP6 (Cla023090) as functional amino acid transporters belonging to the family of amino acid permease (AAP) genes. The yeast growth and uptake assays of radiolabeled amino acid suggested that ClAAP3 and ClAAP6 can transport a broad spectrum of amino acids. Expression of translational fusion proteins with a GFP reporter in Nicotiana benthamiana leaves confirmed the ER- and plasma membrane-specific localization, suggesting the role of ClAAP proteins in the cellular import of amino acids. Based on the gene expression profiles and functional characterization, ClAAP3 and ClAAP6 are expected to play a major role in regulation of amino acid import into developing watermelon fruits.

scholarly journals Characterization of the Candida albicans Amino Acid Permease Family: Gap2 Is the Only General Amino Acid Permease and Gap4 Is an S-Adenosylmethionine (SAM) Transporter Required for SAM-Induced Morphogenesis

mSphere ◽  
2016 ◽  
Vol 1 (6) ◽  
Author(s):  
Lucie Kraidlova ◽  
Sanne Schrevens ◽  
Hélène Tournu ◽  
Griet Van Zeebroeck ◽  
Hana Sychrova ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Candida Albicans ◽  
Amino Acid ◽  
Virulence Factor ◽  
Amino Acid Transporters ◽  
Amino Acid Permease ◽  
Content Type ◽  
Important Virulence Factor ◽  
General Amino Acid Permease

ABSTRACT Candida albicans is a commensal organism that can thrive in many niches in its human host. The environmental conditions at these different niches differ quite a bit, and this fungus must be able to sense these changes and adapt its metabolism to them. Apart from glucose and other sugars, the uptake of amino acids is very important. This is underscored by the fact that the C. albicans genome encodes 6 orthologues of the Saccharomyces. cerevisiae general amino acid permease Gap1 and many other amino acid transporters. In this work, we characterize these six permeases and we show that C. albicans Gap2 is the functional orthologue of ScGap1 and that C. albicans Gap4 is an orthologue of ScSam3, an S-adenosylmethionine (SAM) transporter. Furthermore, we show that Gap4 is required for SAM-induced morphogenesis, an important virulence factor of C. albicans. Amino acids are key sources of nitrogen for growth of Candida albicans. In order to detect and take up these amino acids from a broad range of different and changing nitrogen sources inside the host, this fungus must be able to adapt via its expression of genes for amino acid uptake and further metabolism. We analyzed six C. albicans putative general amino acid permeases based on their homology to the Saccharomyces cerevisiae Gap1 general amino acid permease. We generated single- and multiple-deletion strains and found that, based on growth assays and transcriptional or posttranscriptional regulation, Gap2 is the functional orthologue to ScGap1, with broad substrate specificity. Expression analysis showed that expression of all GAP genes is under control of the Csy1 amino acid sensor, which is different from the situation in S. cerevisiae, where the expression of ScGAP1 is not regulated by Ssy1. We show that Gap4 is the functional orthologue of ScSam3, the only S-adenosylmethionine (SAM) transporter in S. cerevisiae, and we report that Gap4 is required for SAM-induced morphogenesis. IMPORTANCE Candida albicans is a commensal organism that can thrive in many niches in its human host. The environmental conditions at these different niches differ quite a bit, and this fungus must be able to sense these changes and adapt its metabolism to them. Apart from glucose and other sugars, the uptake of amino acids is very important. This is underscored by the fact that the C. albicans genome encodes 6 orthologues of the Saccharomyces. cerevisiae general amino acid permease Gap1 and many other amino acid transporters. In this work, we characterize these six permeases and we show that C. albicans Gap2 is the functional orthologue of ScGap1 and that C. albicans Gap4 is an orthologue of ScSam3, an S-adenosylmethionine (SAM) transporter. Furthermore, we show that Gap4 is required for SAM-induced morphogenesis, an important virulence factor of C. albicans.

scholarly journals First Insights into the Genome Sequence of the Alkaliphilic Thermotolerant Bacterium Clostridium thermoalcaliphilum JW/YL23-2T

2017 ◽  
Vol 5 (20) ◽  
Author(s):  
Anja Poehlein ◽  
Alexandra Berg ◽  
Gina Welsing ◽  
Rolf Daniel
Keyword(s):  
Amino Acids ◽  
Sewage Sludge ◽  
Genome Sequence ◽  
Draft Genome ◽  
Protein Coding ◽  
Content Type ◽  
Protein Coding Genes ◽  
Obligate Anaerobic ◽  
Casamino Acids ◽  
Thermotolerant Bacterium

ABSTRACT Clostridium thermoalcaliphilum is an obligate anaerobic and rod-shaped bacterium isolated from sewage sludge. It is an alkaliphilic thermotolerant organism and utilizes sucrose, glucose, fructose, maltose, cellobiose, amino acids, and Casamino Acids as substrates. The draft genome comprises 2.031 Mbp and 2,027 predicted protein-coding genes.

scholarly journals Cloning, Expression, and Functional Characterization of Secondary Amino Acid Transporters of Lactococcus lactis

2012 ◽  
Vol 195 (2) ◽  
pp. 340-350 ◽  
Author(s):  
Hein Trip ◽  
Niels L. Mulder ◽  
Juke S. Lolkema
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Lactococcus Lactis ◽  
Aromatic Amino Acids ◽  
Amino Acid Transporter ◽  
Amino Acid Transporters ◽  
Acid Uptake ◽  
Content Type ◽  
Secondary Amino ◽  
Acid Transporter

ABSTRACTFourteen genes encoding putative secondary amino acid transporters were identified in the genomes ofLactococcus lactissubsp.cremorisstrains MG1363 and SK11 andL. lactissubsp. lactisstrains IL1403 and KF147, 12 of which were common to all four strains. Amino acid uptake inL. lactiscells overexpressing the genes revealed transporters specific for histidine, lysine, arginine, agmatine, putrescine, aromatic amino acids, acidic amino acids, serine, and branched-chain amino acids. Substrate specificities were demonstrated by inhibition profiles determined in the presence of excesses of the other amino acids. Four knockout mutants, lacking the lysine transporter LysP, the histidine transporter HisP (formerly LysQ), the acidic amino acid transporter AcaP (YlcA), or the aromatic amino acid transporter FywP (YsjA), were constructed. The LysP, HisP, and FywP deletion mutants showed drastically decreased rates of uptake of the corresponding substrates at low concentrations. The same was observed for the AcaP mutant with aspartate but not with glutamate. In rich M17 medium, the deletion of none of the transporters affected growth. In contrast, the deletion of the HisP, AcaP, and FywP transporters did affect growth in a defined medium with free amino acids as the sole amino acid source. HisP was essential at low histidine concentrations, and AcaP was essential in the absence of glutamine. FywP appeared to play a role in retaining intracellularly synthesized aromatic amino acids when these were not added to the medium. Finally, HisP, AcaP, and FywP did not play a role in the excretion of accumulated histidine, glutamate, or phenylalanine, respectively, indicating the involvement of other transporters.

scholarly journals Selective Requirement of the Shikimate Pathway of Legionella pneumophila for Intravacuolar Growth within Human Macrophages but Not within Acanthamoeba

2015 ◽  
Vol 83 (6) ◽  
pp. 2487-2495 ◽  
Author(s):  
Snake C. Jones ◽  
Christopher T. D. Price ◽  
Marina Santic ◽  
Yousef Abu Kwaik
Keyword(s):  
Amino Acids ◽  
Legionella Pneumophila ◽  
De Novo ◽  
Shikimate Pathway ◽  
Aromatic Amino Acids ◽  
Human Monocyte ◽  
Optimal Growth ◽  
Growth Defect ◽  
Content Type ◽  
Human Macrophages

Legionella pneumophilautilizes the Dot/Icm type IV translocation system to proliferate within a vacuole in a wide variety of natural amoebal hosts and in alveolar macrophages of the human accidental host. AlthoughL. pneumophilautilizes host amino acids as the main sources of carbon and energy, it is not known whetherde novosynthesis of amino acids by intravacuolarL. pneumophilacontributes to its nutrition. ThearoBandaroEgenes encode enzymes for the shikimate pathway that generates the aromatic amino acids Phe, Trp, and Tyr. Here we show thearoBandaroEmutants ofL. pneumophilato be defective in growth in human monocyte-derived macrophages (hMDMs) but not inAcanthamoebaspp. ThearoBandaroEmutants are severely attenuated in intrapulmonary proliferation in the A/J mouse model of Legionnaires' disease, and the defect is fully complemented by the respective wild-type alleles. The two mutants grow normally in rich media but do not grow in defined media lacking aromatic amino acids, and the growth defect is rescued by inclusion of the aromatic amino acids, which are essential for production of the pyomelanin pigment. Interestingly, supplementation of infected hMDMs with the three aromatic amino acids or with Trp alone rescues the intramacrophage defect of thearoEbut not thearoBmutant. Therefore, the shikimate pathway ofL. pneumophilais differentially required for optimal growth within human macrophages, which are auxotrophic for Trp and Phe, but is dispensable for growth within theAcanthamoebaspp. that synthesize the aromatic amino acids.

scholarly journals Tailoring a Global Iron Regulon to a Uropathogen

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Rajdeep Banerjee ◽  
Erin Weisenhorn ◽  
Kevin J. Schwartz ◽  
Kevin S. Myers ◽  
Jeremy D. Glasner ◽  
...  
Keyword(s):  
Amino Acids ◽  
Urinary Tract ◽  
Amino Acid ◽  
Regulatory Network ◽  
Iron Homeostasis ◽  
Iron Limitation ◽  
Content Type ◽  
E Coli ◽  
General Stress ◽  
K 12

ABSTRACT Pathogenicity islands and plasmids bear genes for pathogenesis of various Escherichia coli pathotypes. Although there is a basic understanding of the contribution of these virulence factors to disease, less is known about variation in regulatory networks in determining disease phenotypes. Here, we dissected a regulatory network directed by the conserved iron homeostasis regulator, ferric uptake regulator (Fur), in uropathogenic E. coli (UPEC) strain CFT073. Comparing anaerobic genome-scale Fur DNA binding with Fur-dependent transcript expression and protein levels of the uropathogen to that of commensal E. coli K-12 strain MG1655 showed that the Fur regulon of the core genome is conserved but also includes genes within the pathogenicity/genetic islands. Unexpectedly, regulons indicative of amino acid limitation and the general stress response were also indirectly activated in the uropathogen fur mutant, suggesting that induction of the Fur regulon increases amino acid demand. Using RpoS levels as a proxy, addition of amino acids mitigated the stress. In addition, iron chelation increased RpoS to the same levels as in the fur mutant. The increased amino acid demand of the fur mutant or iron chelated cells was exacerbated by aerobic conditions, which could be partly explained by the O2-dependent synthesis of the siderophore aerobactin, encoded by an operon within a pathogenicity island. Taken together, these data suggest that in the iron-poor environment of the urinary tract, amino acid availability could play a role in the proliferation of this uropathogen, particularly if there is sufficient O2 to produce aerobactin. IMPORTANCE Host iron restriction is a common mechanism for limiting the growth of pathogens. We compared the regulatory network controlled by Fur in uropathogenic E. coli (UPEC) to that of nonpathogenic E. coli K-12 to uncover strategies that pathogenic bacteria use to overcome iron limitation. Although iron homeostasis functions were regulated by Fur in the uropathogen as expected, a surprising finding was the activation of the stringent and general stress responses in the uropathogen fur mutant, which was rescued by amino acid addition. This coordinated global response could be important in controlling growth and survival under nutrient-limiting conditions and during transitions from the nutrient-rich environment of the lower gastrointestinal (GI) tract to the more restrictive environment of the urinary tract. The coupling of the response of iron limitation to increased demand for amino acids could be a critical attribute that sets UPEC apart from other E. coli pathotypes.

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