scholarly journals The Novel Monocomponent FAD-dependent Monooxygenase HpaM Catalyzes the 2-Decarboxylative Hydroxylation of 5-Hydroxypicolinic Acid inAlcaligenes faecalisJQ135

2017 ◽  
Author(s):  
Jiguo Qiu ◽  
Bin Liu ◽  
Lingling Zhao ◽  
Yanting Zhang ◽  
Dan Cheng ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Microbial Degradation ◽  
Pyridine Ring ◽  
Degradation Process ◽  
Alcaligenes Faecalis ◽  
Pyridine Derivative ◽  
Pyridine Derivatives ◽  
Monooxygenase Activity ◽  
E Coli ◽  
Transformation Mechanisms

Abstract5-hydroxypicolinic acid (5HPA) is a natural pyridine derivative that can be microbially degraded. However, the physiological, biochemical, and genetic foundation of the microbial catabolism of 5HPA remains unknown. In this study, a gene clusterhpa(which is involved in degradation of 5HPA inAlcaligenes faecalisJQ135) was cloned and HpaM was identified as a novel monocomponent FAD-dependent monooxygenase. HpaM shared a sequence only 31% similarity with the most related protein 6-hydroxynicotinate 3-monooxygenase (NicC) ofPseudomonas putidaKT2440.hpaMwas heterologously expressed inE. coliBL21(DE3), and the recombinant HpaM was purified via Ni-affinity chromatography. HpaM catalyzed the 2-decarboxylative hydroxylation of 5-HPA, thus generating 2,5-dihydroxypyridine (2,5-DPH). Monooxygenase activity was only detected in the presence of FAD and NADH, but not of FMN and NADPH. The apparentKmvalues of HpaM toward 5HPA and NADH were 45.4 μ and 37.8 μ, respectively. Results of gene deletion and complementation showed thathpaMwas essential for 5HPA degradation inAlcaligenes faecalisJQ135.ImportancePyridine derivatives are ubiquitous in nature and important chemical materials that are currently widely used in agriculture, pharmaceutical, and chemical industries. Thus, the microbial degradation and transformation mechanisms of pyridine derivatives received considerable attention. Decarboxylative hydroxylation was an important degradation process in pyridine derivatives, and previously reported decarboxylative hydroxylations happened in the C3 of the pyridine ring. In this study, we cloned the gene clusterhpa, which is responsible for 5HPA degradation inAlcaligenes faecalisJQ135, thus identifying a novel monocomponent FAD-dependent monooxygenase HpaM. Unlike 3-decarboxylative monooxygenases, HpaM catalyzed decarboxylative hydroxylation in the C2 of the pyridine ring in 5-hydroxypicolinic acid. These findings deepen our understanding of the molecular mechanism of microbial degradation of pyridine derivatives. Furthermore, HpaM offers potential for applications to transform useful pyridine derivatives.

scholarly journals A Novel Degradation Mechanism for Pyridine Derivatives inAlcaligenes faecalisJQ135

2018 ◽  
Vol 84 (15) ◽  
Author(s):  
Jiguo Qiu ◽  
Bin Liu ◽  
Lingling Zhao ◽  
Yanting Zhang ◽  
Dan Cheng ◽  
...  
Keyword(s):  
Nicotinic Acid ◽  
Maleic Acid ◽  
Degradation Mechanism ◽  
Picolinic Acid ◽  
Alcaligenes Faecalis ◽  
Pyridine Derivative ◽  
Pyridine Derivatives ◽  
Monooxygenase Activity ◽  
Content Type ◽  
Gene Coding

ABSTRACT5-Hydroxypicolinic acid (5HPA), a natural pyridine derivative, is microbially degraded in the environment. However, the physiological, biochemical, and genetic foundations of 5HPA metabolism remain unknown. In this study, an operon (hpa), responsible for 5HPA degradation, was cloned fromAlcaligenes faecalisJQ135. HpaM was a monocomponent flavin adenine dinucleotide (FAD)-dependent monooxygenase and shared low identity (only 28 to 31%) with reported monooxygenases. HpaM catalyzed theorthodecarboxylative hydroxylation of 5HPA, generating 2,5-dihydroxypyridine (2,5DHP). The monooxygenase activity of HpaM was FAD and NADH dependent. The apparentKmvalues of HpaM for 5HPA and NADH were 45.4 μM and 37.8 μM, respectively. The geneshpaX,hpaD, andhpaFwere found to encode 2,5DHP dioxygenase,N-formylmaleamic acid deformylase, and maleamate amidohydrolase, respectively; however, the three genes were not essential for 5HPA degradation inA. faecalisJQ135. Furthermore, the genemaiA, which encodes a maleic acidcis-transisomerase, was essential for the metabolism of 5HPA, nicotinic acid, and picolinic acid inA. faecalisJQ135, indicating that it might be a key gene in the metabolism of pyridine derivatives. The genes and proteins identified in this study showed a novel degradation mechanism of pyridine derivatives.IMPORTANCEUnlike the benzene ring, the uneven distribution of the electron density of the pyridine ring influences the positional reactivity and interaction with enzymes; e.g., theorthoandparaoxidations are more difficult than themetaoxidations. Hydroxylation is an important oxidation process for the pyridine derivative metabolism. In previous reports, theorthohydroxylations of pyridine derivatives were catalyzed by multicomponent molybdenum-containing monooxygenases, while themetahydroxylations were catalyzed by monocomponent FAD-dependent monooxygenases. This study identified the new monocomponent FAD-dependent monooxygenase HpaM that catalyzed theorthodecarboxylative hydroxylation of 5HPA. In addition, we found that themaiAgene coding for maleic acidcis-transisomerase was pivotal for the metabolism of 5HPA, nicotinic acid, and picolinic acid inA. faecalisJQ135. This study provides novel insights into the microbial metabolism of pyridine derivatives.

Multinuclear NMR spectra of [Pt(L)Cl3]− (L = pyridine derivatives) complexes and crystal structure of trans-Pt(2,6-di(hydroxymethyl)pyridine)2Cl2•2H2O

1996 ◽  
Vol 74 (11) ◽  
pp. 2121-2130 ◽  
Author(s):  
Fernande D. , ◽  
Corinne Bensimon ◽  
André L. Beauchamp
Keyword(s):  
Crystal Structure ◽  
Pyridine Ring ◽  
Chemical Shifts ◽  
Bond Distance ◽  
Coupling Constants ◽  
Mirror Plane ◽  
Pyridine Derivative ◽  
Pyridine Derivatives ◽  
Pyridine Ligand ◽  
Twofold Axis

Complexes of the type [Pt(L)Cl3]− (L = pyridine derivative) were synthesized and studied by 13C and 195Pt NMR spectroscopies. The 195Pt signals were observed between −1720 and −1897 ppm. No correlation between the δ(Pt) and the pKa of the protonated pyridine derivatives was found. The chemical shifts vary with the substituents on the pyridine ligand. Compounds with substituents in ortho positions were observed at lower fields, except for complexes containing hydroxy or amine groups. The latter compounds were observed at higher fields, close to the signals of the Pt-unsubstituted pyridine compound. These results were explained in terms of the solvent effect. The chemical shifts δ(C) and the coupling constants J(13C–195Pt) were measured and the results interpreted with a view of obtaining information on the nature of the Pt—N bond. The possibility of π-bonding between platinum and the pyridine ligand is examined. The conformation of the pyridine ring in relation to the platinum plane and the energies of the rotation barriers around the Pt—N bond in these types of platinum(II) complexes are briefly discussed. The crystal structure of trans-Pt(2,6-(HOCH2)2py)2Cl2•2H2O was determined by X-ray diffraction. The compound is monoclinic, C2/m, a = 7.022(6), b = 15.646(13), c = 8.344(10) Å, β = 93.35(8)°, Z = 2, R = 0.037. The platinum atom is located at the junction of the twofold axis and the mirror plane, the N atoms and the para-C atom of the pyridine ring are situated on the twofold axis, and the chloride ligands are on the mirror plane. The compound crystallizes with molecules of water, which are H-bonded to the hydroxy groups. The Pt—Cl bond distance is 2.306(2) Å, and that of the Pt—N bond is 2.041 (6) Å. The dihedral angle between the platinum and the pyridine planes is 79.8°. Key words: platinum, pyridine derivatives, NMR, crystal structure.

scholarly journals Identification and characterization of a novelpicgene cluster responsible for picolinic acid degradation inAlcaligenes faecalisJQ135

2019 ◽  
Author(s):  
Jiguo Qiu ◽  
Lingling Zhao ◽  
Siqiong Xu ◽  
Qing Chen ◽  
Le Chen ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Molecular Mechanisms ◽  
Tricarboxylic Acid Cycle ◽  
Picolinic Acid ◽  
Gene Clusters ◽  
Alcaligenes Faecalis ◽  
Pyridine Derivative ◽  
Complete Degradation ◽  
Important Intermediate ◽  
New Perspective

AbstractPicolinic acid (PA) is a natural toxic pyridine derivative. Microorganisms can degrade and utilize PA for growth. However, the full metabolic pathway and its physiological and genetic foundation remain unknown. In this study, we identified thepicgene cluster responsible for the complete degradation of PA fromAlcaligenes faecalisJQ135. PA was initially 6-hydroxylated into 6-hydroxypicolinic acid (6HPA) by PA dehydrogenase (PicA). 6HPA was then 3-hydroxylated by a four-component 6HPA monooxygenase (PicB) to form 3,6-dihydroxypicolinic acid (3,6DHPA), which was then converted into 2,5-dihydroxypyridine (2,5DHP) by a decarboxylase (PicC). The 2,5DHP was further degraded into fumaric acid, through PicD (2,5DHP dioxygenase), PicE (N-formylmaleamic acid deformylase), PicF (maleamic acid amidohydrolase), and PicG (maleic acid isomerase). Homologouspicgene clusters with diverse organizations were found to be widely distributed inα-,β-, andγ-Proteobacteria. Our findings provide new insights into the microbial metabolism of environmental toxic pyridine derivatives.ImportancePicolinic acid is a common metabolite of L-tryptophan and some aromatic compounds and is an important intermediate of industrial concern. Although the microbial degradation/detoxification of picolinic acid has been studied for over 50 years, the underlying molecular mechanisms are still unknown. Here, we show thepicgene cluster responsible for the complete degradation of picolinic acid into the tricarboxylic acid cycle. This gene cluster was found to be widespread in otherα-,β-, andγ-Proteobacteria. These findings provide new perspective for understanding the mechanisms of picolinic acid biodegradation in bacteria.

scholarly journals Catabolism of 3-hydroxypyridine by Ensifer adhaerens HP1: a novel four-component gene encoding 3-hydroxypyridine dehydrogenase HpdA catalyzes the first step of biodegradation

2020 ◽  
Author(s):  
Haixia Wang ◽  
Xiaoyu Wang ◽  
Hao Ren ◽  
Xuejun Wang ◽  
Zhenmei Lu
Keyword(s):  
Gene Cluster ◽  
Microbial Degradation ◽  
Molecular Mechanisms ◽  
Gene Clusters ◽  
Sole Source ◽  
Pyridine Derivative ◽  
Gene Encoding ◽  
Ensifer Adhaerens ◽  
Important Building Block ◽  
Component Gene

Abstract3-Hydroxypyridine (3HP) is an important natural pyridine derivative. Ensifer adhaerens HP1 can utilize 3HP as the sole source of carbon, nitrogen and energy to grow. However, the genes responsible for the degradation of 3HP remain unknown. In this study, we predicted that a gene cluster, designated 3hpd, may be responsible for the degradation of 3HP. The initial hydroxylation of 3HP is catalyzed by a four-component dehydrogenase (HpdA1A2A3A4), leading to the formation of 2,5-dihydroxypyridine (2,5-DHP) in E. adhaerens HP1. In addition, the SRPBCC component in HpdA existed as a separate subunit, which is different from other SRPBCC-containing molybdohydroxylases acting on N-heterocyclic aromatic compounds. Our findings provide a better understanding of the microbial degradation of pyridine derivatives in nature. Additionally, research on the origin of the discovered four-component dehydrogenase with a separate SRPBCC domain may be of great significance.Importance3-Hydroxypyridine is an important building block for synthesizing drugs, herbicides and antibiotics. Although the microbial degradation of 3-hydroxypyridine has been studied for many years, the molecular mechanisms remain unclear. Here, we show that 3hpd is responsible for the catabolism of 3-hydroxypyridine. The 3hpd gene cluster was found to be widespread in Actinobacteria, Rubrobacteria, Thermoleophilia, and Alpha-, Beta-, and Gammaproteobacteria, and the genetic organization of the 3hpd gene clusters in these bacteria showed high diversity. Our findings provide new insight into the catabolism of 3-hydroxypyridine in bacteria.

scholarly journals 3-Hydroxypyridine Dehydrogenase HpdA Is Encoded by a Novel Four-Component Gene Cluster and Catalyzes the First Step of 3-Hydroxypyridine Catabolism in Ensifer adhaerens HP1

2020 ◽  
Vol 86 (19) ◽  
Author(s):  
Haixia Wang ◽  
Xiaoyu Wang ◽  
Hao Ren ◽  
Xuejun Wang ◽  
Zhenmei Lu
Keyword(s):  
Gene Cluster ◽  
Microbial Degradation ◽  
Molecular Mechanisms ◽  
Gene Clusters ◽  
Pyridine Derivative ◽  
Pyruvate Phosphate Dikinase ◽  
Content Type ◽  
Ensifer Adhaerens ◽  
Microbial Strains ◽  
Important Building Block

ABSTRACT 3-Hydroxypyridine (3HP) is an important natural pyridine derivative. Ensifer adhaerens HP1 can utilize 3HP as its sole sources of carbon, nitrogen, and energy to grow, but the genes responsible for the degradation of 3HP remain unknown. In this study, we predicted that a gene cluster, designated 3hpd, might be responsible for the degradation of 3HP. The analysis showed that the initial hydroxylation of 3HP in E. adhaerens HP1 was catalyzed by a four-component dehydrogenase (HpdA1A2A3A4) and led to the formation of 2,5-dihydroxypyridine (2,5-DHP). In addition, the SRPBCC component in HpdA existed as a separate subunit, which is different from other SRPBCC-containing molybdohydroxylases acting on N-heterocyclic aromatic compounds. Moreover, the results demonstrated that the phosphoenolpyruvate (PEP)-utilizing protein and pyruvate-phosphate dikinase were involved in the HpdA activity, and the presence of the gene cluster 3hpd was discovered in the genomes of diverse microbial strains. Our findings provide a better understanding of the microbial degradation of pyridine derivatives in nature and indicated that further research on the origin of the discovered four-component dehydrogenase with a separate SRPBCC domain and the function of PEP-utilizing protein and pyruvate-phosphate dikinase might be of great significance. IMPORTANCE 3-Hydroxypyridine is an important building block for the synthesis of drugs, herbicides, and antibiotics. Although the microbial degradation of 3-hydroxypyridine has been studied for many years, the molecular mechanisms remain unclear. Here, we show that 3hpd is responsible for the catabolism of 3-hydroxypyridine. The 3hpd gene cluster was found to be widespread in Actinobacteria, Rubrobacteria, Thermoleophilia, and Alpha-, Beta-, and Gammaproteobacteria, and the genetic organization of the 3hpd gene clusters in these bacteria shows high diversity. Our findings provide new insight into the catabolism of 3-hydroxypyridine in bacteria.

scholarly journals Identification and Characterization of a NovelpicGene Cluster Responsible for Picolinic Acid Degradation inAlcaligenes faecalisJQ135

2019 ◽  
Vol 201 (16) ◽  
Author(s):  
Jiguo Qiu ◽  
Lingling Zhao ◽  
Siqiong Xu ◽  
Qing Chen ◽  
Le Chen ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Molecular Mechanisms ◽  
Picolinic Acid ◽  
Gene Clusters ◽  
Alcaligenes Faecalis ◽  
Degradation Pathway ◽  
Pyridine Derivative ◽  
Organic Chemical ◽  
Content Type ◽  
New Perspective

ABSTRACTPicolinic acid (PA) is a natural toxic pyridine derivative. Microorganisms can degrade and utilize PA for growth. However, the full catabolic pathway of PA and its physiological and genetic foundation remain unknown. In this study, we identified a gene cluster, designatedpicRCEDFB4B3B2B1A1A2A3, responsible for the degradation of PA fromAlcaligenes faecalisJQ135. Our results suggest that PA degradation pathway occurs as follows: PA was initially 6-hydroxylated to 6-hydroxypicolinic acid (6HPA) by PicA (a PA dehydrogenase). 6HPA was then 3-hydroxylated by PicB, a four-component 6HPA monooxygenase, to form 3,6-dihydroxypicolinic acid (3,6DHPA), which was then converted into 2,5-dihydroxypyridine (2,5DHP) by the decarboxylase PicC. 2,5DHP was further degraded to fumaric acid through PicD (2,5DHP 5,6-dioxygenase), PicE (N-formylmaleamic acid deformylase), PicF (maleamic acid amidohydrolase), and PicG (maleic acid isomerase). Homologouspicgene clusters with diverse organizations were found to be widely distributed inAlpha-,Beta-, andGammaproteobacteria. Our findings provide new insights into the microbial catabolism of environmental toxic pyridine derivatives.IMPORTANCEPicolinic acid is a common metabolite ofl-tryptophan and some aromatic compounds and is an important intermediate in organic chemical synthesis. Although the microbial degradation/detoxification of picolinic acid has been studied for over 50 years, the underlying molecular mechanisms are still unknown. Here, we show that thepicgene cluster is responsible for the complete degradation of picolinic acid. Thepicgene cluster was found to be widespread in otherAlpha-,Beta-, andGammaproteobacteria. These findings provide a new perspective for understanding the catabolic mechanisms of picolinic acid in bacteria.

Synthesis and Reactivity of Precolibactin 886

2019 ◽  
Author(s):  
Seth Herzon ◽  
Alan R. Healy ◽  
kevin wernke ◽  
Chung Sub Kim ◽  
Nicholas Lees ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Gene Cluster ◽  
Amino Alcohol ◽  
Biomimetic Synthesis ◽  
Cross Linking ◽  
E Coli ◽  
Hplc Purification ◽  
Structural Assignment ◽  
Biosynthetic Precursor ◽  
Double Oxidation

<div>The clb gene cluster encodes the biosynthesis of metabolites known as precolibactins and colibactins. The clb pathway is found in gut commensal E. coli, and clb metabolites are thought to initiate colorectal cancer via DNA cross-linking. Precolibactin 886 (1) is one of the most complex isolated clb metabolites; it contains a 15-atom macrocycle and an unusual 5-hydroxy-3-oxazoline ring. Here we report confirmation of the structural assignment via a biomimetic synthesis of precolibactin 886 (1) proceeding through the amino alcohol 9. Double oxidation of 9 afforded the unstable α-ketoimine 2 which underwent macrocyclization to precolibactin 886 (1) upon HPLC purification (3% from 9). Studies of the putative precolibactin 886 (1) biosynthetic precursor 2, the model α-ketoimine 25, and the α-dicarbonyl 26 revealed that these compounds are susceptible to nucleophilic rupture of the C36–C37 bond. Moreover, cleavage of 2 produces other known clb metabolites or biosynthetic intermediates. This unexpected reactivity explains the difficulties in isolating full clb metabolites and accounts for the structure of a recently identified colibactin–adenine adduct. The colibactin peptidase ClbP deacylates synthetic precolibactin 886 (1) to form a non-genotoxic pyridone, suggesting precolibactin 886 (1) lies off-path of the major biosynthetic route.</div>

scholarly journals Identification of the Biosynthetic Gene Cluster for 3-Methylarginine, a Toxin Produced by Pseudomonas syringae pv. syringae 22d/93

2010 ◽  
Vol 76 (8) ◽  
pp. 2500-2508 ◽  
Author(s):  
S. D. Braun ◽  
J. Hofmann ◽  
A. Wensing ◽  
M. S. Ullrich ◽  
H. Weingart ◽  
...  
Keyword(s):  
Amino Acid ◽  
Gene Cluster ◽  
Pseudomonas Syringae ◽  
Biosynthetic Gene Cluster ◽  
Pentanoic Acid ◽  
Promising Candidate ◽  
Biosynthesis Gene Cluster ◽  
E Coli ◽  
Highly Active ◽  
Putative Aminotransferase

ABSTRACT The epiphyte Pseudomonas syringae pv. syringae 22d/93 (Pss22d) produces the rare amino acid 3-methylarginine (MeArg), which is highly active against the closely related soybean pathogen Pseudomonas syringae pv. glycinea. Since these pathogens compete for the same habitat, Pss22d is a promising candidate for biocontrol of P. syringae pv. glycinea. The MeArg biosynthesis gene cluster codes for the S-adenosylmethionine (SAM)-dependent methyltransferase MrsA, the putative aminotransferase MrsB, and the amino acid exporter MrsC. Transfer of the whole gene cluster into Escherichia coli resulted in heterologous production of MeArg. The methyltransferase MrsA was overexpressed in E. coli as a His-tagged protein and functionally characterized (Km , 7 mM; k cat, 85 min−1). The highly selective methyltransferase MrsA transfers the methyl group from SAM into 5-guanidino-2-oxo-pentanoic acid to yield 5-guanidino-3-methyl-2-oxo-pentanoic acid, which then only needs to be transaminated to result in the antibiotic MeArg.

scholarly journals A Bacterial Microcompartment Is Used for Choline Fermentation byEscherichia coli536

2018 ◽  
Vol 200 (10) ◽  
Author(s):  
Taylor I. Herring ◽  
Tiffany N. Harris ◽  
Chiranjit Chowdhury ◽  
Sujit Kumar Mohanty ◽  
Thomas A. Bobik
Keyword(s):  
Electron Microscopy ◽  
Heart Disease ◽  
Gene Cluster ◽  
Transcriptional Regulator ◽  
Human Gut ◽  
Content Type ◽  
E Coli ◽  
Bacterial Microcompartment ◽  
New Type ◽  
Insight Into

ABSTRACTBacterial choline degradation in the human gut has been associated with cancer and heart disease. In addition, recent studies found that a bacterial microcompartment is involved in choline utilization byProteusandDesulfovibriospecies. However, many aspects of this process have not been fully defined. Here, we investigate choline degradation by the uropathogenEscherichia coli536. Growth studies indicatedE. coli536 degrades choline primarily by fermentation. Electron microscopy indicated that a bacterial microcompartment was used for this process. Bioinformatic analyses suggested that the choline utilization (cut) gene cluster ofE. coli536 includes two operons, one containing three genes and a main operon of 13 genes. Regulatory studies indicate that thecutXgene encodes a positive transcriptional regulator required for induction of the maincutoperon in response to choline supplementation. Each of the 16 genes in thecutcluster was individually deleted, and phenotypes were examined. ThecutX,cutY,cutF,cutO,cutC,cutD,cutU, andcutVgenes were required for choline degradation, but the remaining genes of thecutcluster were not essential under the conditions used. The reasons for these varied phenotypes are discussed.IMPORTANCEHere, we investigate choline degradation inE. coli536. These studies provide a basis for understanding a new type of bacterial microcompartment and may provide deeper insight into the link between choline degradation in the human gut and cancer and heart disease. These are also the first studies of choline degradation inE. coli536, an organism for which sophisticated genetic analysis methods are available. In addition, thecutgene cluster ofE. coli536 is located in pathogenicity island II (PAI-II536) and hence might contribute to pathogenesis.

scholarly journals Prevalence of the “High-Pathogenicity Island” of Yersinia Species among Escherichia coliStrains That Are Pathogenic to Humans

1998 ◽  
Vol 66 (2) ◽  
pp. 480-485 ◽  
Author(s):  
S. Schubert ◽  
A. Rakin ◽  
H. Karch ◽  
E. Carniel ◽  
J. Heesemann
Keyword(s):  
Gene Cluster ◽  
Yersinia Pseudotuberculosis ◽  
Pathogenicity Island ◽  
Uptake System ◽  
Highly Pathogenic ◽  
E Coli ◽  
Yersinia Species ◽  
The Family ◽  
High Pathogenicity ◽  
Dna Sequence Comparison

ABSTRACT The fyuA-irp gene cluster contributes to the virulence of highly pathogenic Yersinia (Yersinia pestis,Yersinia pseudotuberculosis, and Yersinia enterocolitica 1B). The cluster encodes an iron uptake system mediated by the siderophore yersiniabactin and reveals features of a pathogenicity island. Two evolutionary lineages of this “high pathogenicity island” (HPI) can be distinguished on the basis of DNA sequence comparison: a Y. pestis group and a Y. enterocolitica group. In this study we demonstrate that the HPI of the Y. pestis evolutionary group is disseminated among species of the family Enterobacteriaceae which are pathogenic to humans. It prevails in enteroaggregativeEscherichia coli and in E. coli blood culture isolates (93 and 80%, respectively), but is rarely found in enteropathogenic E. coli, enteroinvasive E. coli, and enterotoxigenic E. coli isolates. In contrast, the HPI was absent from enterohemorrhagic E. coli, Shigella, and Salmonella entericastrains investigated. Polypeptides encoded by the fyuA,irp1, and irp2 genes located on the HPI could be detected in E. coli strains pathogenic to humans. However, these E. coli strains showed a reduced sensitivity to the bacteriocin pesticin, whose uptake is mediated by the FyuA receptor. Escherichia strains do not possess thehms gene locus thought to be a part of the HPI of Y. pestis. Deletions of the fyuA-irp gene cluster affecting solely the fyuA part of the HPI were identified in 3% of the E. coli strains tested. These results suggest horizontal transfer of the HPI between Y. pestis and some pathogenic E. coli strains.

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