Basement membrane carbohydrate as a target for bacterial adhesion: binding of type I fimbriae of Salmonella enterica and Escherichia coli to laminin

Adherence of type-1-fimbriate Salmonella enterica and Escherichia coli to immobilized proteins of the extracellular matrix and reconstituted basement membranes was studied. The type-1-fimbriate strain SH401 of S. enterica serovar Enteritidis showed good adherence to laminin, whereas the adherence to fibronectin, type I, type III, type IV or type V collagens was poor. Only minimal adherence to the matrix proteins was seen with a non-fimbriate strain of S. enterica serovar Typhimurium. A specific and mannoside-inhibitable adhesion to laminin was exhibited by the recombinant E. coli strain HB101(plSF101) possessing fim genes of Typhimurium. Adherence to laminin of strain SH401 was inhibited by Fab fragments against purified SH401 fimbriae, and a specific binding to laminin, of the purified fimbriae, was demonstrated using fimbriae-coated fluorescent microparticles. Periodate treatment of laminin abolished the bacterial adhesion as well as the fimbrial binding. Specific adhesion to immobilized laminin was also shown by the type-1 -fimbriate E. coli strain 2131 and the recombinant strain E. coli HB101(pPKL4) expressing the cloned type-1-fimbriae genes of E. coli. Adhesion to laminin of strain HB101(pPKL4) was inhibited by mannoside, and no adherence was seen with the fimH mutant E. coli HB101(pPKL5/pPKL53) lacking the fimbrial lectin subunit. The type-1 fimbriate strains also adhered to reconstituted basement membranes from mouse sarcoma cells and human placenta. Adhesion of strains HB101(plSF101) and HB101(pPKL4) to both basement membrane preparations was inhibited by mannoside. We conclude that type-1 fimbriae of S. enterica and E. coli bind to oMgomannoside chains of the lamjnjn network in basement membranes.     

Overproduction of AgfA subunit of Salmonella enteritidis as a MBP-fusion protein in E. coli

To study the characteristics of recombinant thin aggregative fimbriae of salmonella and to develop a vaccine for salmonella infections, the AgfA subunit gene was amplified from Salmonella entiritidis using PCR. Maltose binding protein (MBP)-AgfA fusion protein was over-produced in E. coli and purified. Antibody against MBP-AgfA was prepared and its immunogenicity was studied.     

Identification of two protein-binding and functional regions of curli,a surface organelle and virulence determinant of Escherichia coli

Curli are surface organelles of Escherichia coli. These fibrous proteins, formed by polymerization of a 15-kDa subunit, are expressed by E. coli strains associated with severe infections in humans. A remarkable property of curli is their ability to interact with a wide range of human proteins, interactions that contribute to the enhanced virulence of curli-expressing E. coli. To define the protein-binding region(s) of curli, we investigated the binding properties of overlapping synthetic peptides covering the curli subunit. Two peptides, one covering a 24-amino acid residue sequence in the NH(2)-terminal half of the subunit (NNS24) and one corresponding to the 26 COOH-terminal residues (VDQ26), were found to bind a number of human proteins. Physiochemical analysis revealed that NNS24 adopts a thermally stable beta-structure, and in solution the peptide forms soluble multimers, predominantly octamers. Intact curli are known to activate the proinflammatory and procoagulant contact system, and when added to human plasma, the NNS24 and VDQ26 peptides induced the release of the potent vasoactive peptide bradykinin. The results map important curli functions to the regions corresponding to the NNS24 and VDQ26 sequences.     

Unique fimbriae-like structures encoded by sefD of the SEF14 fimbrial gene cluster of Salmonella enteritidis

The SEF14 gene cluster of Salmonella enteritidis was recently shown to contain three genes, sefABC, encoding a unique fimbrin, and proteins homologous to fimbrial chaperones and outer membrane proteins (ushers), respectively. A fourth open reading frame, designated sefD, was found immediately downstream of sefABC and overlapping sefC. The translated protein sequence of sefD was unique, but the composition was similar to that of other bacterial fimbriae. SefD was produced in abundance by wild-type S. enteritidis as shown by Western blot analysis using antibodies raised to affinity-purified, recombinant SefD. Furthermore, unusually long, thin, fimbriae-like structures were evident on S. enteritidis and Escherichia coli by immunoelectron microscopy, but in other bacterial species SefD was expressed as amorphous material. Therefore, in S. enteritidis and E. coli, SefD is the predominant structural subunit of SEF18. The SEF18 fimbriae-like structures were shown to be serologically distinct from the three known S. enteritidis fimbriae SEF14, SEF17 and SEF21. Furthermore, SEF18 was still produced in set A insertion mutants, indicating that SEF14 and SEF18 were structurally distinct. Thus, the SEF14 gene cluster is the first example in the Enterobacteriaceae of a gene cluster that encodes two fimbrin-like proteins, which are assembled into two distinct cell-surface structures, SEF14 and SEF1B. DNA hybridization and Western blot analyses showed that SefD was widely distributed among the Enterobacteriaceae and was present in E. coli, Shigella, Enterobacter, Citrobacter, Erwinia, Hafnia, Klebsiella, Providencia, and Proteus but not in the non-Enterobacteriaceae Gram-negative bacteria Pseudomonas and Aeromonas, or in Gram-positive bacteria Bacillus or Staphylococcus. Immunoelectron microscopy revealed that sefD was also present on the surface of Providencia and Klebsiella but did not appear filamentous. This is the first instance of highly conserved, thin fimbriaelike structers which are ubiquitous among the Enterobacteriaceae.     

The variant rpoS allele of S. enteritidis strain 27655R does not affect virulence in a chick model nor constitutive curliation but does generate a cold-sensitive phenotype

Adherence of pathogenic Escherichia coli and Salmonella spp. to host cells is in part mediated by curli fimbriae which, along with other virulence determinants, are positively regulated by RpoS. Interested in the role and regulation of curli (SEF17) fimbriae of Salmonella enteritidis in poultry infection, we tested the virulence of naturally occurring S. enteritidis PT4 strains 27655R and 27655S which displayed constitutive and null expression of curli (SEF17) fimbriae, respectively, in a chick invasion assay and analysed their rpoS alleles. Both strains were shown to be equally invasive and as invasive as a wild-type phage type 4 strain and an isogenic derivative defective for the elaboration of curli. We showed that the rpoS allele of 27655S was intact even though this strain was non-curliated and we confirmed that a S. enteritidis rpoS::str^r null mutant was unable to express curli, as anticipated. Strain 27655R, constitutively curliated, possessed a frameshift mutation at position 697 of the rpoS coding sequence which resulted in a truncated product and remained curliated even when transduced to rpoS::str^r. Additionally, rpoS mutants are known to be cold-sensitive, a phenotype confirmed for strain 27655R. Collectively, these data indicated that curliation was not a significant factor for pathogenesis of S. enteritidis in this model and that curliation of strains 27655R and 27655S was independent of RpoS. Significantly, strain 27655R possessed a defective rpoS allele and remained virulent. Here was evidence that supported the concept that different naturally occurring rpoS alleles may generate varying virulence phenotypic traits.     

Phospholipid-associated annexin A2-S100A10 heterotetramer and its subunits: characterization of the interaction with tissue plasminogen activator,plasminogen, and plasmin

Annexin A2 (p36) is a highly alpha-helical molecule that consists of two opposing sides, a convex side that contains the phospholipid-binding sites and a concave side, which faces the extracellular milieu and contains multiple ligand-binding sites. The amino-terminal region of annexin A2 extends along the concave side of the protein and contains the binding site for the S100A10 (p11) subunit. The interaction of these subunits results in the formation of the heterotetrameric form of the protein, annexin A2-S100A10 heterotetramer (AIIt). To simulate the orientation of AIIt on the plasma membrane we bound AIIt to a phospholipid bilayer that was immobilized on a BIAcore biosensor chip. Surface plasmon resonance was used to observe in real time the molecular interactions between phospholipid-associated AIIt or its annexin A2 subunit and the ligands, tissue-type plasminogen activator (t-PA), plasminogen, and plasmin. AIIt bound t-PA (Kd = 0.68 microm), plasminogen (Kd = 0.11 microm), and plasmin (Kd = 75 nm) with moderate affinity. Contrary to previous reports, the phospholipid-associated annexin A2 subunit failed to bind t-PA or plasminogen but bound plasmin (Kd = 0.78 microm). The S100A10 subunit bound t-PA (Kd = 0.45 microm), plasminogen (Kd = 1.81 microm), and plasmin (Kd = 0.36 microm). Removal of the carboxyl-terminal lysines from the S100A10 subunit attenuated t-PA and plasminogen binding to AIIt. These results show that the carboxyl-terminal lysines of S100A10 form t-PA and plasminogen-binding sites. In contrast, annexin A2 and S100A10 contain distinct binding sites for plasmin.     

Thin, aggregative fimbriae mediate binding of Salmonella enteritidis to fibronectin.

The binding of human fibronectin and Congo red by an autoaggregative Salmonella enteritidis strain was found to be dependent on its ability to produce thin, aggregative fimbriae, named SEF 17 (for Salmonella enteritidis fimbriae with an apparent fimbrin molecular mass of 17 kDa). Two other fimbrial types produced by S. enteritidis, SEF 14 and SEF 21, were not responsible for the aggregative phenotype or for fibronectin binding. SEF 17-negative TnphoA mutants which retained the ability to produce SEF 14 and SEF 21 were unable to bind human fibronectin or Congo red and lost the ability to autoaggregate. Only purified SEF 17 but not purified SEF 14 or SEF 21 bound fibronectin in a solid-phase binding assay. Furthermore, only SEF 17 was able to inhibit fibronectin binding to S. enteritidis whole cells in a direct competition enzyme-linked immunosorbent assay. These results indicate that SEF 17 are the fimbriae responsible for binding fibronectin by this enteropathogen.     

Fibrin structures during tissue-type plasminogen activator-mediated fibrinolysis studied by laser light scattering: relation to fibrin enhancement of plasminogen activation

The aim was to relate fibrin structure and the stimulatory effect of fibrin on plasminogen activation during t-PA-mediated fibrinolysis using Lys⁷⁸-plasminogen as activator substrate. Structural studies were undertaken by static and dynamic laser light scattering, cryo transmission electron microscopy and by the measurement of conversion of fibrin to X-, Y- and D-fragments. The kinetics of plasmin formation were monitored by measurement of the rate of pNA-release from Val-LeuLys-pNA. The process of fibrin formation and degradation comprised three phases. In the first phase, protofibrils with an average length of about 10 times that of fibrinogen were formed. The duration of this phase decreased with increasing t-PA concentration. The second phase was characterized by a sudden elongation and lateral aggregation of fibrin fibers, most pronounced at low levels of t-PA, and by formation of fragment X-polymer. The third phase was dominated by fragmentation of fibers and by formation of Y- and D-fragments: Plasmin degraded the fibers from within, resulting in the formation of long loose bundles, which subsequently disintegrated into thin filaments with a length of less than 10 and a mass per length close to one relative to fibrinogen. Plasmin generation at high t-PA concentrations sets in just prior to (and at low t-PA concentrations shortly after) the onset of the rapid second phase of elongation and lateral aggregation of fibrin fibers. The maximal rate of plasmin formation per mol t-PA was the same at all concentrations of activator and was achieved close to the time of the peak level of fragment X-polymer. Plasmin formation ceased after formation of substantial amounts of Y- and D-fragments. At this stage the length was between 300 and 3 and the mass per length close to 1, both relative to fibrinogen. In conclusion our results indicate that (1) formation of short fibrin protofibrils is the minimal requirement for the onset of the stimulatory effect of fibrin on plasminogen activation by t-PA, (2) formation of fragment X protofibrils is sufficient to induce optimal stimulation of plasminogen activation, and (3) plasmin degrades laterally aggregated fibrin fibers from within, resulting in the conversion of the fibers into long loose bundles, which later disintegrate into thin filaments.Abbreviations t-PA tissue-type plasminogen activator - Lys⁷⁸-plasminogen plasmin-modified plasminogen, mainly with NH₂-terminal lysine (residues 78-791, residue numbering according to Forsgren et al. 1987) - Val-Leu-Lys-pNA H-D-valyl-L-leucyl-L-lysine-4-nitroanilide - Phe-Pip-Arg-pNA H-D-phenylalanyl-L-arginine-4-nitroanilide - pNA p-nitroanilide - SDS sodium dodecyl sulphate The present work has been supported by the Danish Natural Science Research Council and the Danish Agricultural and Veterinary Research CouncilDeceased on August 2, 1991 Correspondence to: R. Bauer     

Uropathogenic Escherichia coli Modulates Immune Responses and Its Curli Fimbriae Interact with the Antimicrobial Peptide LL-37

Bacterial growth in multicellular communities, or biofilms, offers many potential advantages over single-cell growth, including resistance to antimicrobial factors. Here we describe the interaction between the biofilm-promoting components curli fimbriae and cellulose of uropathogenic E. coli and the endogenous antimicrobial defense in the urinary tract. We also demonstrate the impact of this interplay on the pathogenesis of urinary tract infections. Our results suggest that curli and cellulose exhibit differential and complementary functions. Both of these biofilm components were expressed by a high proportion of clinical E. coli isolates. Curli promoted adherence to epithelial cells and resistance against the human antimicrobial peptide LL-37, but also increased the induction of the proinflammatory cytokine IL-8. Cellulose production, on the other hand, reduced immune induction and hence delayed bacterial elimination from the kidneys. Interestingly, LL-37 inhibited curli formation by preventing the polymerization of the major curli subunit, CsgA. Thus, even relatively low concentrations of LL-37 inhibited curli-mediated biofilm formation in vitro. Taken together, our data demonstrate that biofilm components are involved in the pathogenesis of urinary tract infections by E. coli and can be a target of local immune defense mechanisms.     

Leishmania mexicana: LACK (Leishmania homolog of receptors for activated C-kinase) is a plasminogen binding protein

Leishmania mexicana is able to interact with the fibrinolytic system through its component plasminogen, the zymogenic form of the protease plasmin. In this study a new plasminogen binding protein of this parasite was identified: LACK, the Leishmania homolog of receptors for activated C-kinase. Plasminogen binds recombinant LACK with a K_d value of 1.6 ± 0.4 μM, and binding is lysine-dependent since it is inhibited by the lysine analog ε-aminocaproic acid. Inhibition studies with specific peptides and plasminogen binding activity of a mutated recombinant LACK have highlighted the internal motif ₂₆₀VYDLESKAV₂₆₈, similar to those found in several enolases, as involved in plasminogen binding. Recombinant LACK and secreted proteins, in medium conditioned by parasites, enhance plasminogen activation to plasmin by the tissue plasminogen activator (t-PA). In addition to its localization in the cytosol, in the microsomal fraction and as secreted protein in conditioned medium, LACK was also localized on the external surface of the membrane. The results presented here suggest that LACK might bind and enhance plasminogen activation in vivo promoting the formation of plasmin. Plasminogen binding of LACK represents a new function for this protein and might contribute to the invasiveness of the parasite.     

Involvement of curli fimbriae in the biofilm formation of Enterobacter cloacae

In this study, we examined the biofilm forming ability, the mRNA expression of curli genes and the morphologies of curli fimbriae and biofilms in clinical isolates of Enterobacter cloacae. The csgBA operon was found in 11 (78.6%) of the 14 isolates. The ability of E. cloacae isolates to form biofilms was significantly correlated with the mRNA expression level of the csgA and csgD genes. The curli protein fimbriae appeared as tangled fibers and the curli-proficient strain formed mature biofilms. Our data suggest that the expression of the curli fimbriae play an important role in biofilm formation in E. cloacae.     

The Polymorphic Aggregative Phenotype of Shiga Toxin-Producing Escherichia coli O111 Depends on RpoS and Curli

Escherichia coli O111 is an emerging non-O157:H7 serotype of Shiga toxin-producing E. coli (STEC). We previously reported that outbreak and environmental, but not sporadic-case, strains of STEC O111 share a distinct aggregation phenotype (M. E. Diodati, A. H. Bates, M. B. Cooley, S. Walker, R. E. Mandrell, and M. T. Brandl, Foodborne Pathog Dis 12:235−243, 2015, http://dx.doi.org/10.1089/fpd.2014.1887). We show here the natural occurrence of nonaggregative variants in single STEC O111 strains. These variants do not produce curli fimbriae and lack RpoS function but synthesize cellulose. The deletion of csgBAC or rpoS in an aggregative outbreak strain abolished aggregate formation, which was rescued when curli biogenesis or RpoS function, respectively, was restored. Complementation of a nonaggregative variant with RpoS also conferred curli production and aggregation. These observations were supported by Western blotting with an anti-CsgA antibody. Immunomicroscopy revealed that curli were undetectable on the cells of the nonaggregative variant and the RpoS mutant but were present in large quantities in the intercellular matrix of the assemblages formed by aggregative strains. Sequence analysis of rpoS in the aggregative strain and its variant showed a single substitution of threonine for asparagine at amino acid 124. Our results indicate that the multicellular behavior of STEC O111 is RpoS dependent via positive regulation of curli production. Aggregation may confer a fitness advantage in O111 outbreak strains under stressful conditions in hydrodynamic environments along the food production chain and in the host, while the occurrence of nonaggregative variants may allow the cell population to adapt to conditions benefiting a planktonic lifestyle.     

Evidence for the Binding of Ng-CAM to Laminin

Ng-CAM is a cell adhesion molecule mediating neuron-glia and neuron-neuron adhesion via different binding mechanisms. While its binding can be homophilic as demonstrated by the self-aggregation of Ng-CAM coated beads (Covaspheres), Ng-CAM has also been shown to bind to glia by a heterophilic mechanism. In the present study, we found that the extent of Ng-CAM Covasphere aggregation was strongly diminished in the presence of the extracellular matrix glycoprotein laminin. When proteolytic fragments of laminin were tested, the P1′ fragment (obtained from the short arms by pepsin treatment) was found to inhibit aggregation of Ng-CAM-Covaspheres while the elastase fragments E3 and E8 (from the long arm) were ineffective. To provide other means of analyzing interactions between laminin and Ng-CAM, the two proteins were covalently linked to differently fluorescing Covaspheres and tested for coaggregation. Laminin-Covaspheres coaggregated with Ng-CAM-Covaspheres, and this binding was inhibited both by anti-Ng-CAM and by anti-laminin antibodies. Covaspheres coated with other proteins including BSA and fibronectin did not coaggregate with Ng-CAM-Covaspheres. Moreover, using a solid phase binding assay, we found that ¹²⁵I-labeled Ng-CAM bound to laminin and to Ng-CAM but not to fibronectin. The results suggest that regions in the short arms of laminin can bind to Ng-CAM. To test whether Ng-CAM present on neurons could be involved in binding to laminin, adhesion of neurons to substrates coated with various proteins was tested in the presence of specific antibodies. Anti-Ng-CAM Fab' fragments inhibited neuronal binding to laminin but not binding to fibronectin. The combined results open the possibility that Ng-CAM on the surface of neurons may mediate binding to laminin in vivo, and that interactions with laminin can modulate homophilic Ng-CAM binding.     

Thrombomodulin lacking the cytoplasmic domain efficiently internalizes thrombin via nonclathrin-coated,pit-mediated endocytosis

The plasminogen activation (PA) system of human Co 115 colon carcinoma cells was investigated. Analysis at the levels of protein and mRNA of cultured cells and of histozymography of tumor xenografts in nude mice showed that Co 115 cells produce only tissue type PA (t-PA) and no urokinase (u-PA). Also, mRNA for the u-PA receptor and for PA inhibitorr type 2 (PAI-2), but not for PAI-I, were detected. We developed a quantitative degradation assay using glutaraldehyde-immobilized¹²⁵I-Iaminin to investigate the capacity of Co 115 cells to degrade laminin. Laminin degradation by Co 115 cells was completely inhibited by 100 μg/ml of polyclonal anti-t-PA IgG, by the plasmin inhibitors aprotinin (100μg/ml) or ε-aminocaproic acid (EACA; at 0.3 M), but not by antibodies against u-PA or u-PAR nor by nonimmune IgG. Cycloheximide-treated Co 115 cells were unable to degrade laminin but increased laminin degradation induced by conditioned medium of Co 115 cells or recombinant t-PA. No potentiation was observed when Co 115 cells and laminin were kept separated by Transwell™ inserts. Our results suggest that Co 115 human colon carcinoma cells degrade laminin by potentiating t-PA-mediated plasminogen activaton at the cells surface which requires close contact between tumor cells and laminin substrate. © 1994 Wiley-Liss, Inc.     

Epitope Specificity of a Monoclonal Antibody Generated against the Dissociated CFA/I Fimbriae of Enterotoxigenic Escherichia coli

A monoclonal antibody (MAb 84) raised against the dissociated CFA/I fimbriae of enterotoxigenic Escherichia coli was characterized with regard to antigen binding and epitope specificity. Enzyme-linked immunosorbent assay (ELISA) showed that MAb 84 had higher affinity to CFA/I subunits than to intact CFA/I fimbriae and recognized a Salmonella flagellin carrying an insert corresponding to amino acids 32 to 45 of the CFA/I subunit. Fine epitope mapping based on the Pepscan technique showed that the peptide ³⁹TFESY⁴³, derived from the sequence of the mature CFA/I subunit, was specifically recognized by MAb 84. The ³⁹TFESY⁴³ sequence is probably not accessible on the surface of the native CFA/I fimbriae since MAb 84 did not bind to intact fimbriae as evaluated in inhibition ELISA tests. Moreover, MAb 84 did not agglutinate fimbriated ETEC cells nor inhibit CFA/I-mediated hemagglutination or the adhesion to Caco-2 cells.     

Growth, Survival and Characterization of cspA in Salmonella enteritidis Following Cold Shock

Salmonella enteritidis is a major foodborne microbial pathogen that can grow and survive at low temperatures for a considerable period of time. Increased survival was evidenced from a frozen S. enteritidis culture when treated at 10°C prior to freezing. Western blot analysis with Escherichia coli CspA antibody and analysis of radiolabeled proteins from S. enteritidis cultures after cold shock at 10°C and 5°C showed increased expression of a 7.4-kDa major cold shock protein, CS7.4, similar in size to that reported for E. coli. Cloning followed by nucleotide sequence analysis of the cspA gene from S. enteritidis showed a 100% nucleotide sequence identity in the promoter elements (−35 and −10) and the amino acid sequence encoded by the open reading frame (ORF) with the E. coli cspA gene. However, the differences in the nucleotide sequences between E. coli and S. enteritidis cspA genes in the putative repressor protein binding domain, the fragment 7, and in various segments throughout the upstream 0.642-kbp DNA may contribute to the expression of CS7.4 at less stringent temperatures in S. enteritidis. As in E. coli, the actual role of CS7.4 in protecting S. enteritidis from the damaging effects of cold or freezing temperatures is not yet understood. Received: 14 March 1997 / Accepted: 10 July 1997     

Promiscuous Cross-seeding between Bacterial Amyloids Promotes Interspecies Biofilms

Amyloids are highly aggregated proteinaceous fibers historically associated with neurodegenerative conditions including Alzheimers, Parkinsons, and prion-based encephalopathies. Polymerization of amyloidogenic proteins into ordered fibers can be accelerated by preformed amyloid aggregates derived from the same protein in a process called seeding. Seeding of disease-associated amyloids and prions is highly specific and cross-seeding is usually limited or prevented. Here we describe the first study on the cross-seeding potential of bacterial functional amyloids. Curli are produced on the surface of many Gram-negative bacteria where they facilitate surface attachment and biofilm development. Curli fibers are composed of the major subunit CsgA and the nucleator CsgB, which templates CsgA into fibers. Our results showed that curli subunit homologs from Escherichia coli, Salmonella typhimurium LT2, and Citrobacter koseri were able to cross-seed in vitro. The polymerization of Escherichia coli CsgA was also accelerated by fibers derived from a distant homolog in Shewanella oneidensis that shares less than 30% identity in primary sequence. Cross-seeding of curli proteins was also observed in mixed colony biofilms with E. coli and S. typhimurium. CsgA was secreted from E. coli csgB− mutants assembled into fibers on adjacent S. typhimurium that presented CsgB on its surfaces. Similarly, CsgA was secreted by S. typhimurium csgB− mutants formed curli on CsgB-presenting E. coli. This interspecies curli assembly enhanced bacterial attachment to agar surfaces and supported pellicle biofilm formation. Collectively, this work suggests that the seeding specificity among curli homologs is relaxed and that heterogeneous curli fibers can facilitate multispecies biofilm development.     

The green tea polyphenol EGCG inhibits E. coli biofilm formation by impairing amyloid curli fibre assembly and downregulating the biofilm regulator CsgD via the σE‐dependent sRNA RybB

In bacterial biofilms, which are often involved in chronic infections, cells are surrounded by a self‐produced extracellular matrix that contains amyloid fibres, exopolysaccharides and other biopolymers. The matrix contributes to the pronounced resistance of biofilms against antibiotics and host immune systems. Being highly inflammatory, matrix amyloids such as curli fibres of Escherichia coli can also play a role in pathogenicity. Using macrocolony biofilms of commensal and pathogenic E. coli as a model system, we demonstrate here that the green tea polyphenol epigallocatachin gallate (EGCG) is a potent antibiofilm agent. EGCG virtually eliminates the biofilm matrix by directly interfering with the assembly of curli subunits into amyloid fibres, and by triggering the σ^E cell envelope stress response and thereby reducing the expression of CsgD – a crucial activator of curli and cellulose biosynthesis – due to csgD mRNA targeting by the σ^E‐dependent sRNA RybB. These findings highlight EGCG as a potential adjuvant for antibiotic therapy of biofilm‐associated infections. Moreover, EGCG may support therapies against pathogenic E. coli that produce inflammatory curli fibres along with Shigatoxin.