Bacterial Secretions of Nonpathogenic Escherichia coli Elicit Inflammatory Pathways: a Closer Investigation of Interkingdom Signaling

ABSTRACTThere have been many studies on the relationship between nonpathogenic bacteria and human epithelial cells; however, the bidirectional effects of the secretomes (secreted substances in which there is no direct bacterium-cell contact) have yet to be fully investigated. In this study, we use a transwell model to explore the transcriptomic effects of bacterial secretions from two different nonpathogenicEscherichia colistrains on the human colonic cell line HCT-8 using next-generation transcriptome sequencing (RNA-Seq).E. coliBL21 and W3110, while genetically very similar (99.1% homology), exhibit key phenotypic differences, including differences in their production of macromolecular structures (e.g., flagella and lipopolysaccharide) and in their secretion of metabolic byproducts (e.g., acetate) and signaling molecules (e.g., quorum-sensing autoinducer 2 [AI-2]). After analysis of differential epithelial responses to the respective secretomes, this study shows for the first time that a nonpathogenic bacterial secretome activates the NF-κB-mediated cytokine-cytokine receptor pathways while also upregulating negative-feedback components, including the NOD-like signaling pathway. Because of AI-2's relevance as a bacterium-bacterium signaling molecule and the differences in its secretion rates between these strains, we investigated its role in HCT-8 cells. We found that the expression of the inflammatory cytokine interleukin 8 (IL-8) responded to AI-2 with a pattern of rapid upregulation before subsequent downregulation after 24 h. Collectively, these data demonstrate that secreted products from nonpathogenic bacteria stimulate the transcription of immune-related biological pathways, followed by the upregulation of negative-feedback elements that may serve to temper the inflammatory response.IMPORTANCEThe symbiotic relationship between the microbiome and the host is important in the maintenance of human health. There is a growing need to further understand the nature of these relationships to aid in the development of homeostatic probiotics and also in the design of novel antimicrobial therapeutics. To our knowledge, this is the first global-transcriptome study of bacteria cocultured with human epithelial cells in a model to determine the transcriptional effects of epithelial cells in which epithelial and bacterial cells are allowed to “communicate” with each other only through diffusible small molecules and proteins. By beginning to demarcate the direct and indirect effects of bacteria on the gastrointestinal (GI) tract, two-way interkingdom communication can potentially be mediated between host and microbe.

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PBP4 and PBP5 are involved in regulating exopolysaccharide synthesis during Escherichia coli biofilm formation

Microbiology ◽

10.1099/mic.0.001031 ◽

2021 ◽

Vol 167 (3) ◽

Author(s):

Sathi Mallick ◽

Shanti Kiran ◽

Tapas Kumar Maiti ◽

Anindya S. Ghosh

Keyword(s):

Escherichia Coli ◽

Biofilm Formation ◽

Type Species ◽

Pentose Phosphate ◽

Bacterial Cells ◽

Surface Adhesion ◽

Content Type ◽

Penicillin Binding Proteins ◽

E Coli ◽

Link Type

Escherichia coli low-molecular-mass (LMM) Penicillin-binding proteins (PBPs) help in hydrolysing the peptidoglycan fragments from their cell wall and recycling them back into the growing peptidoglycan matrix, in addition to their reported involvement in biofilm formation. Biofilms are external slime layers of extra-polymeric substances that sessile bacterial cells secrete to form a habitable niche for themselves. Here, we hypothesize the involvement of Escherichia coli LMM PBPs in regulating the nature of exopolysaccharides (EPS) prevailing in its extra-polymeric substances during biofilm formation. Therefore, this study includes the assessment of physiological characteristics of E. coli CS109 LMM PBP deletion mutants to address biofilm formation abilities, viability and surface adhesion. Finally, EPS from parent CS109 and its ΔPBP4 and ΔPBP5 mutants were purified and analysed for sugars present. Deletions of LMM PBP reduced biofilm formation, bacterial adhesion and their viability in biofilms. Deletions also diminished EPS production by ΔPBP4 and ΔPBP5 mutants, purification of which suggested an increased overall negative charge compared with their parent. Also, EPS analyses from both mutants revealed the appearance of an unusual sugar, xylose, that was absent in CS109. Accordingly, the reason for reduced biofilm formation in LMM PBP mutants may be speculated as the subsequent production of xylitol and a hindrance in the standard flow of the pentose phosphate pathway.

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Comparative Analysis of EspF Variants in Inhibition of Escherichia coli Phagocytosis by Macrophages and Inhibition of E. coli Translocation through Human- and Bovine-Derived M Cells

Infection and Immunity ◽

10.1128/iai.00023-11 ◽

2011 ◽

Vol 79 (11) ◽

pp. 4716-4729 ◽

Cited By ~ 19

Author(s):

Amin Tahoun ◽

Gabriella Siszler ◽

Kevin Spears ◽

Sean McAteer ◽

Jai Tree ◽

...

Keyword(s):

Escherichia Coli ◽

Epithelial Cells ◽

Cellular Localization ◽

M Cells ◽

Binding Assays ◽

M Cell ◽

Content Type ◽

E Coli ◽

Coculture System

ABSTRACTThe EspF protein is secreted by the type III secretion system of enteropathogenic and enterohemorrhagicEscherichia coli(EPEC and EHEC, respectively). EspF sequences differ between EHEC O157:H7, EHEC O26:H11, and EPEC O127:H6 in terms of the number of SH3-binding polyproline-rich repeats and specific residues in these regions, as well as residues in the amino domain involved in cellular localization. EspFO127is important for the inhibition of phagocytosis by EPEC and also limits EPEC translocation through antigen-sampling cells (M cells). EspFO127has been shown to have effects on cellular organelle function and interacts with several host proteins, including N-WASP and sorting nexin 9 (SNX9). In this study, we compared the capacities of differentespFalleles to inhibit (i) bacterial phagocytosis by macrophages, (ii) translocation through an M-cell coculture system, and (iii) uptake by and translocation through cultured bovine epithelial cells. TheespFgene fromE. coliserotype O157 (espFO157) allele was significantly less effective at inhibiting phagocytosis and also had reduced capacity to inhibitE. colitranslocation through a human-derivedin vitroM-cell coculture system in comparison toespFO127andespFO26. In contrast,espFO157was the most effective allele at restricting bacterial uptake into and translocation through primary epithelial cells cultured from the bovine terminal rectum, the predominant colonization site of EHEC O157 in cattle and a site containing M-like cells. Although LUMIER binding assays demonstrated differences in the interactions of the EspF variants with SNX9 and N-WASP, we propose that other, as-yet-uncharacterized interactions contribute to the host-based variation in EspF activity demonstrated here.

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Impacts of Hematite Nanoparticle Exposure on Biomechanical, Adhesive, and Surface Electrical Properties of Escherichia coli Cells

Applied and Environmental Microbiology ◽

10.1128/aem.00193-12 ◽

2012 ◽

Vol 78 (11) ◽

pp. 3905-3915 ◽

Cited By ~ 50

Author(s):

Wen Zhang ◽

Joseph Hughes ◽

Yongsheng Chen

Keyword(s):

Escherichia Coli ◽

Electrical Properties ◽

Current Knowledge ◽

Statistical Significance ◽

Spring Constant ◽

Bacterial Cells ◽

Kelvin Probe ◽

Content Type ◽

Force Microscopy ◽

E Coli

ABSTRACTDespite a wealth of studies examining the toxicity of engineered nanomaterials, current knowledge on their cytotoxic mechanisms (particularly from a physical perspective) remains limited. In this work, we imaged and quantitatively characterized the biomechanical (hardness and elasticity), adhesive, and surface electrical properties ofEscherichia colicells with and without exposure to hematite nanoparticles (NPs) in an effort to advance our understanding of the cytotoxic impacts of nanomaterials. Both scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed thatE. colicells had noticeable deformation with hematite treatment for 45 min with a statistical significance. The hematite-treated cells became significantly harder or stiffer than untreated ones, as evidenced by indentation and spring constant measurements. The average indentation of the hematite-treatedE. colicells was 120 nm, which is significantly lower (P< 0.01) than that of the untreated cells (approximately 400 nm). The spring constant of hematite-treatedE. colicells (0.28 ± 0.11 nN/nm) was about 20 times higher than that of untreated ones (0.01 ± 0.01 nN/nm). The zeta potential ofE. colicells, measured by dynamic light scattering (DLS), was shown to shift from −4 ± 2 mV to −27 ± 8 mV with progressive surface adsorption of hematite NPs, a finding which is consistent with the local surface potential measured by Kelvin probe force microscopy (KPFM). Overall, the reported findings quantitatively revealed the adverse impacts of nanomaterial exposure on physical properties of bacterial cells and should provide insight into the toxicity mechanisms of nanomaterials.

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Fab-Independent Antiadhesion Effects of Secretory Immunoglobulin A on S-Fimbriated Escherichia coli Are Mediated by Sialyloligosaccharides

Infection and Immunity ◽

10.1128/iai.66.8.3971-3973.1998 ◽

1998 ◽

Vol 66 (8) ◽

pp. 3971-3973 ◽

Cited By ~ 52

Author(s):

Horst Schroten ◽

Christoph Stapper ◽

Ricarda Plogmann ◽

Henrik Köhler ◽

Jörg Hacker ◽

...

Keyword(s):

Escherichia Coli ◽

Epithelial Cells ◽

Human Milk ◽

Immunoglobulin A ◽

Secretory Immunoglobulin A ◽

E Coli ◽

Human Epithelial Cells ◽

Early Human ◽

Secretory Immunoglobulin

ABSTRACT S-fimbriated Escherichia coli strains cause sepsis and meningitis in newborns and are known to recognize the carbohydrate sequence sialyl-(α2-3)-galactoside. We show that adhesion of cloned S-fimbriated E. coli to human epithelial cells is inhibited Fab independently by sialyloligosaccharides on secretory immunoglobulin A (s-IgA). This indicates an anti-infective function of s-IgA (Fc), particularly in early human milk.

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Molecular Characterization of the EhaG and UpaG Trimeric Autotransporter Proteins from Pathogenic Escherichia coli

Applied and Environmental Microbiology ◽

10.1128/aem.06680-11 ◽

2012 ◽

Vol 78 (7) ◽

pp. 2179-2189 ◽

Cited By ~ 47

Author(s):

Makrina Totsika ◽

Timothy J. Wells ◽

Christophe Beloin ◽

Jaione Valle ◽

Luke P. Allsopp ◽

...

Keyword(s):

Escherichia Coli ◽

Epithelial Cells ◽

Cell Surface ◽

Specific Binding ◽

Negative Regulator ◽

Passenger Domain ◽

Content Type ◽

E Coli ◽

Ecm Proteins

ABSTRACTTrimeric autotransporter proteins (TAAs) are important virulence factors of many Gram-negative bacterial pathogens. A common feature of most TAAs is the ability to mediate adherence to eukaryotic cells or extracellular matrix (ECM) proteins via a cell surface-exposed passenger domain. Here we describe the characterization of EhaG, a TAA identified from enterohemorrhagicEscherichia coli(EHEC) O157:H7. EhaG is a positional orthologue of the recently characterized UpaG TAA from uropathogenicE. coli(UPEC). Similarly to UpaG, EhaG localized at the bacterial cell surface and promoted cell aggregation, biofilm formation, and adherence to a range of ECM proteins. However, the two orthologues display differential cellular binding: EhaG mediates specific adhesion to colorectal epithelial cells while UpaG promotes specific binding to bladder epithelial cells. The EhaG and UpaG TAAs contain extensive sequence divergence in their respective passenger domains that could account for these differences. Indeed, sequence analyses of UpaG and EhaG homologues from severalE. coligenomes revealed grouping of the proteins in clades almost exclusively represented by distinctE. colipathotypes. The expression of EhaG (in EHEC) and UpaG (in UPEC) was also investigated and shown to be significantly enhanced in anhnsisogenic mutant, suggesting that H-NS acts as a negative regulator of both TAAs. Thus, while the EhaG and UpaG TAAs contain some conserved binding and regulatory features, they also possess important differences that correlate with the distinct pathogenic lifestyles of EHEC and UPEC.

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Shape Changes and Interaction Mechanism of Escherichia coli Cells Treated with Sericin and Use of a Sericin-Based Hydrogel for Wound Healing

Applied and Environmental Microbiology ◽

10.1128/aem.00643-16 ◽

2016 ◽

Vol 82 (15) ◽

pp. 4663-4672 ◽

Cited By ~ 16

Author(s):

Rui Xue ◽

Yalong Liu ◽

Qingsong Zhang ◽

Congcong Liang ◽

Huazhen Qin ◽

...

Keyword(s):

Electron Microscopy ◽

Escherichia Coli ◽

Cell Membrane ◽

Interaction Mechanism ◽

Bacterial Cells ◽

Content Type ◽

E Coli ◽

Membrane Blebbing ◽

Sterile Gauze

ABSTRACTTo verify the interaction mechanism between sericin andEscherichia coli, especially the morphological and structural changes in the bacterial cells, the antimicrobial activity of sericin againstE. colias a model for Gram-negative bacteria was investigated. The antibacterial activity of sericin onE. coliand the interaction mechanism were investigated in this study by analyzing the growth, integrity, and morphology of the bacterial cells following treatment with sericin. The changes in morphology and cellular compositions of bacterial cells treated with sericin were observed by an inverted fluorescence microscope, scanning electron microscopy, and transmission electron microscopy. Changes in electrical conductivity, total sugar concentration of the broth for the bacteria, and protein expression of the bacteria were determined to investigate the permeability of the cell membrane. A sericin-based hydrogel was prepared for anin vivostudy of wound dressing. The results showed that the antibacterial activity of the hydrogel increased with the increase in the concentration of sericin from 10 g/liter to 40 g/liter. The introduction of sericin induces membrane blebbing ofE. colicells caused by antibiotic action on the cell membrane. The cytoplasm shrinkage phenomenon was accompanied by blurring of the membrane wall boundaries. WhenE. colicells were treated with sericin, release of intracellular components quickly increased. The electrical conductivity assay indicated that the charged ions are reduced after exposure to sericin so that the integrity of the cell membrane is weakened and metabolism is blocked. In addition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that sericin hinders the expression of bacterial protein. Sericin may damage the integrity of the bacterial cell membrane, thereby eventually inhibiting the growth and reproduction ofE. coli. Compared to sterile gauze, the sericin-based hydrogel promoted fibroblast cell proliferation and accelerated the formation of granulation tissues and neovessels.IMPORTANCEThe specific relationship and interaction mechanism between sericin andE. colicells were investigated and elucidated. The results show that after 12 h of treatment, sericin molecules induce membrane blebbing ofE. colicells, and the bacteria show decreases in liquidity and permeability of biological membrane, resulting in alterations in the conductivity of the culture medium and the integrity of the outer membrane. The subsequentin vivoresults demonstrate that the sericin-poly(N-isopropylacrylamide-N,N′-methylene-bis-acrylamide [NIPAm-MBA]) hydrogel accelerated wound healing compared to that with sterile gauze, which is a beneficial result for future applications in clinical medicine and the textile, food, and coating industries.

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CsgA Production by Escherichia coli O157:H7 Alters Attachment to Abiotic Surfaces in Some Growth Environments

Applied and Environmental Microbiology ◽

10.1128/aem.00277-11 ◽

2011 ◽

Vol 77 (20) ◽

pp. 7339-7344 ◽

Cited By ~ 15

Author(s):

R. M. Goulter-Thorsen ◽

E. Taran ◽

I. R. Gentle ◽

K. S. Gobius ◽

G. A. Dykes

Keyword(s):

Escherichia Coli ◽

Growth Medium ◽

Epifluorescence Microscopy ◽

Clear Correlation ◽

Bacterial Cells ◽

Content Type ◽

E Coli ◽

Abiotic Surfaces ◽

Significant Difference ◽

Force Mapping

ABSTRACTThe role of curli expression in attachment ofEscherichia coliO157:H7 to glass, Teflon, and stainless steel (SS) was investigated through the creation ofcsgAknockout mutants in two isolates ofE. coliO157:H7. Attachment assays using epifluorescence microscopy and measurements of the force of adhesion of bacterial cells to the substrates using atomic force microscopy (AFM) force mapping were used to determine differences in attachment between wild-type (wt) andcsgA-negative (ΔcsgA) strains following growth in four different media. The hydrophobicity of the cells was determined using contact angle measurements (CAM) and bacterial adhesion to hydrocarbons (BATH). The attachment assay results indicated that ΔcsgAstrains attached to glass, Teflon, and SS surfaces in significantly different numbers than their wt counterparts in a growth medium-dependent fashion (P< 0.05). However, no clear correlation was seen between attachment numbers, surface type, or growth medium. No correlation was seen between BATH and CAM results (R2< 0.70). Hydrophobicity differed between the wt and ΔcsgAin some cases in a growth medium- and method-dependent fashion (P< 0.05). AFM force mapping revealed no significant difference in the forces of adhesion to glass and SS surfaces between wt and ΔcsgAstrains (P> 0.05) but a significantly greater force of adhesion to Teflon for one of the two wt strains than for its ΔcsgAcounterpart (P< 0.05). This study shows that CsgA production byE. coliO157:H7 may alter attachment behavior in some environments; however, further investigation is required in order to determine the exact relationship between CsgA production and attachment to abiotic surfaces.

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Apple Flavonoid Phloretin Inhibits Escherichia coli O157:H7 Biofilm Formation and Ameliorates Colon Inflammation in Rats

Infection and Immunity ◽

10.1128/iai.05580-11 ◽

2011 ◽

Vol 79 (12) ◽

pp. 4819-4827 ◽

Cited By ~ 94

Author(s):

Jin-Hyung Lee ◽

Sushil Chandra Regmi ◽

Jung-Ae Kim ◽

Moo Hwan Cho ◽

Hyungdon Yun ◽

...

Keyword(s):

Escherichia Coli ◽

Epithelial Cells ◽

Biofilm Formation ◽

Pathogenic Bacteria ◽

Antimicrobial Agents ◽

Trinitrobenzene Sulfonic Acid ◽

Content Type ◽

E Coli ◽

Colon Inflammation ◽

K 12

ABSTRACTPathogenic biofilms have been associated with persistent infections due to their high resistance to antimicrobial agents, while commensal biofilms often fortify the host's immune system. Hence, controlling biofilm formation of both pathogenic bacteria and commensal bacteria is important in bacterium-related diseases. We investigated the effect of plant flavonoids on biofilm formation of enterohemorrhagicEscherichia coliO157:H7. The antioxidant phloretin, which is abundant in apples, markedly reducedE. coliO157:H7 biofilm formation without affecting the growth of planktonic cells, while phloretin did not harm commensalE. coliK-12 biofilms. Also, phloretin reducedE. coliO157:H7 attachment to human colon epithelial cells. Global transcriptome analyses revealed that phloretin repressed toxin genes (hlyEandstx2), autoinducer-2 importer genes (lsrACDBF), curli genes (csgAandcsgB), and dozens of prophage genes inE. coliO157:H7 biofilm cells. Electron microscopy confirmed that phloretin reduced fimbria production inE. coliO157:H7. Also, phloretin suppressed the tumor necrosis factor alpha-induced inflammatory responsein vitrousing human colonic epithelial cells. Moreover, in the rat model of colitis induced by trinitrobenzene sulfonic acid (TNBS), phloretin significantly ameliorated colon inflammation and body weight loss. Taken together, our results suggest that the antioxidant phloretin also acts as an inhibitor ofE. coliO157:H7 biofilm formation as well as an anti-inflammatory agent in inflammatory bowel diseases without harming beneficial commensalE. colibiofilms.

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Specific Electromagnetic Effects of Microwave Radiation on Escherichia coli

Applied and Environmental Microbiology ◽

10.1128/aem.01899-10 ◽

2011 ◽

Vol 77 (9) ◽

pp. 3017-3022 ◽

Cited By ~ 44

Author(s):

Yury Shamis ◽

Alex Taube ◽

Natasa Mitik-Dineva ◽

Rodney Croft ◽

Russell J. Crawford ◽

...

Keyword(s):

Escherichia Coli ◽

Cell Membrane ◽

Cell Morphology ◽

Laser Scanning ◽

Simulation Software ◽

Laser Scanning Microscopy ◽

Confocal Laser ◽

Bacterial Cells ◽

Content Type ◽

E Coli

ABSTRACTThe present study investigated the effects of microwave (MW) radiation applied under a sublethal temperature onEscherichia coli. The experiments were conducted at a frequency of 18 GHz and at a temperature below 40°C to avoid the thermal degradation of bacterial cells during exposure. The absorbed power was calculated to be 1,500 kW/m3, and the electric field was determined to be 300 V/m. Both values were theoretically confirmed using CST Microwave Studio 3D Electromagnetic Simulation Software. As a negative control,E. colicells were also thermally heated to temperatures up to 40°C using Peltier plate heating. Scanning electron microscopy (SEM) analysis performed immediately after MW exposure revealed that theE. colicells exhibited a cell morphology significantly different from that of the negative controls. This MW effect, however, appeared to be temporary, as following a further 10-min elapsed period, the cell morphology appeared to revert to a state that was identical to that of the untreated controls. Confocal laser scanning microscopy (CLSM) revealed that fluorescein isothiocyanate (FITC)-conjugated dextran (150 kDa) was taken up by the MW-treated cells, suggesting that pores had formed within the cell membrane. Cell viability experiments revealed that the MW treatment was not bactericidal, since 88% of the cells were recovered after radiation. It is proposed that one of the effects of exposingE. colicells to MW radiation under sublethal temperature conditions is that the cell surface undergoes a modification that is electrokinetic in nature, resulting in a reversible MW-induced poration of the cell membrane.

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Autoinducer 2-DependentEscherichia coliBiofilm Formation Is Enhanced in a Dual-Species Coculture

Applied and Environmental Microbiology ◽

10.1128/aem.02638-17 ◽

2017 ◽

Vol 84 (5) ◽

Cited By ~ 12

Author(s):

Leanid Laganenka ◽

Victor Sourjik

Keyword(s):

Escherichia Coli ◽

Stress Resistance ◽

Bacterial Species ◽

Interspecies Communication ◽

Content Type ◽

Collective Behaviors ◽

E Coli ◽

Autoinducer 2 ◽

Cell Densities

ABSTRACTBiofilms in nature typically consist of multiple species, and microbial interactions are likely to have crucial effects on biofilm development, structure, and functions. The best-understood form of communication within bacterial communities involves the production, release, and detection of signal molecules (autoinducers), known as quorum sensing. Although autoinducers mainly promote intraspecies communication, autoinducer 2 (AI-2) is produced and detected by a variety of bacteria, thus principally allowing interspecies communication. Here we show the importance of AI-2-mediated signaling in the formation of mixed biofilms byEnterococcus faecalisandEscherichia coli. Our results demonstrate that AI-2 produced byE. faecalispromotes collective behaviors ofE. coliat lower cell densities, enhancing autoaggregation ofE. colibut also leading to chemotaxis-dependent coaggregation between the two species. Finally, we show that formation of such mixed dual-species biofilms increases the stress resistance of bothE. coliandE. faecalis.IMPORTANCEThe role of interspecies communication in the development of mixed microbial communities is becoming increasingly apparent, but specific examples of such communication remain limited. The universal signal molecule AI-2 is well known to regulate cell-density-dependent phenotypes of many bacterial species but, despite its potential for interspecies communication, the role of AI-2 in the establishment of multispecies communities is not well understood. In this study, we explore AI-2 signaling in a dual-species community containing two bacterial species that naturally cooccur in their mammalian hosts, i.e.,Escherichia coliandEnterococcus faecalis. We show that active production of AI-2 byE. faecalisallowsE. colito perform collective behaviors at low cell densities. Additionally, AI-2- and chemotaxis-dependent coaggregation withE. faecaliscreates nucleation zones for rapid growth ofE. colimicrocolonies in mixed biofilms and enhances the stress resistance of both species.

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