Curli Biogenesis and Function

Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA.
Annual Review of Microbiology (Impact Factor: 12.18). 02/2006; 60(1):131-47. DOI: 10.1146/annurev.micro.60.080805.142106
Source: PubMed


Curli are the major proteinaceous component of a complex extracellular matrix produced by many Enterobacteriaceae. Curli were first discovered in the late 1980s on Escherichia coli strains that caused bovine mastitis, and have since been implicated in many physiological and pathogenic processes of E. coli and Salmonella spp. Curli fibers are involved in adhesion to surfaces, cell aggregation, and biofilm formation. Curli also mediate host cell adhesion and invasion, and they are potent inducers of the host inflammatory response. The structure and biogenesis of curli are unique among bacterial fibers that have been described to date. Structurally and biochemically, curli belong to a growing class of fibers known as amyloids. Amyloid fiber formation is responsible for several human diseases including Alzheimer's, Huntington's, and prion diseases, although the process of in vivo amyloid formation is not well understood. Curli provide a unique system to study macromolecular assembly in bacteria and in vivo amyloid fiber formation. Here, we review curli biogenesis, regulation, role in biofilm formation, and role in pathogenesis.

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    • "Curli were first discovered in the 247 late 1980s on E. coli strains that caused bovine mastitis and these are mainly involved in 248 adhesion to surfaces, cell aggregation, and biofilm formation (Austin et al., 2008). Curli also 249 mediate host cell adhesion and invasion, and they are potent inducers of the host inflammatory 250 response (Barnhart and Chapman, 2006). Isolates of Salmonella spp. "
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    ABSTRACT: A community-based sessile life style is the normal mode of growth and survival for many bacterial species. Under such conditions, cell-to-cell interactions are inevitable and ultimately lead to the establishment of dense, complex and highly structured biofilm populations encapsulated in a self-produced extracellular matrix and capable of coordinated and collective behavior. Remarkably, in food processing environments, a variety of different bacteria may attach to surfaces, survive, grow, and form biofilms. Salmonella enterica, Listeria monocytogenes, Escherichia coli, and Staphylococcus aureus are important bacterial pathogens commonly implicated in outbreaks of foodborne diseases, while all are known to be able to create biofilms on both abiotic and biotic surfaces. Particularly challenging is the attempt to understand the complexity of inter-bacterial interactions that can be encountered in such unwanted consortia, such as competitive and cooperative ones, together with their impact on the final outcome of these communities (e.g., maturation, physiology, antimicrobial resistance, virulence, dispersal). In this review, up-to-date data on both the intra- and inter-species interactions encountered in biofilms of these pathogens are presented. A better understanding of these interactions, both at molecular and biophysical levels, could lead to novel intervention strategies for controlling pathogenic biofilm formation in food processing environments and thus improve food safety.
    Frontiers in Microbiology 09/2015; 6:841. DOI:10.3389/fmicb.2015.00841 · 3.99 Impact Factor
    • "Nonetheless , E. coli is well known to express various adhesins, including several FnBPs. The amyloid fibers curli, involved in biofilm formation , are the most important and were previously identified in all OII E. coli studied (Barnhart and Chapman 2006; Henderson et al. 2011; Crémet et al. 2012). Approximately 60% (12/20) of our E. coli strains demonstrated a strong affinity for the curli-binding dye, congo red (data not shown), including both most adherent strains, Ec6 and Ec12. "
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    ABSTRACT: Escherichia coli is one of the first causes of Gram-negative orthopedic implant infections (OII), but little is known about the pathogenicity of this species in such infections that are increasing due to the ageing of the population. We report how this pathogen interacts with human osteoblastic MG-63 cells in vitro, by comparing twenty OII E. coli strains to two Staphylococcus aureus and two Pseudomonas aeruginosa strains. LDH release assay revealed that 6/20 (30%) OII E. coli induced MG-63 cell lysis whereas none of the 4 control strains was cytotoxic after 4 hours of coculture. This high cytotoxicity was associated with hemolytic properties and linked to hlyA gene expresssion. We further showed by gentamicin protection assay and confocal microscopy that the non-cytotoxic E. coli were not able to invade MG-63 cells unlike S. aureus strains (internalization rate < 0.01% for the non-cytotoxic E. coli versus 8.88 ± 2.31% and 4.60 ± 0.42% for both S. aureus). The non-cytotoxic E. coli also demonstrated low adherence rates (<7%), the most adherent E. coli eliciting higher IL-6 and TNF-α mRNA expression in the osteoblastic cells. Either highly cytotoxic or slightly invasive, OII E. coli do not show the same infection strategies as S. aureus towards osteoblasts. © FEMS 2015. All rights reserved. For permissions, please e-mail:
    Pathogens and Disease 09/2015; 73(8). DOI:10.1093/femspd/ftv065 · 2.40 Impact Factor
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    • "A major protein component is curli (amyloid fimbriae), encoded by csg operons (Yaron and Römling 2014). Protein BapA constitutes another important component of the matrix (Barnhart and Chapman 2006) and major biofilm exopolysaccharides are cellulose (Zogaj et al. 2001) and colonic acid (Gibson et al. 2006). Adhesionmediated type I fimbriae, Lpf and Pef, also contribute to the early steps of biofilm formation (Ledeboer et al. 2006). "
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    ABSTRACT: Nearly all bacterial species, including pathogens, have the ability to form biofilms. Biofilms are defined as structured ecosystems in which microbes are attached to surfaces and embedded in a matrix composed of polysaccharides, eDNA, and proteins, and their development is a multistep process. Bacterial biofilms constitute a large medical problem due to their extremely high resistance to various types of therapeutics, including conventional antibiotics. Several environmental and genetic signals control every step of biofilm development and dispersal. From among the latter, quorum sensing, cyclic diguanosine-5'-monophosphate, and small RNAs are considered as the main regulators. The present review describes the control role of these three regulators in the life cycles of biofilms built by Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella enterica serovar Typhimurium, and Vibrio cholerae. The interconnections between their activities are shown. Compounds and strategies which target the activity of these regulators, mainly quorum sensing inhibitors, and their potential role in therapy are also assessed.
    Journal of applied genetics 08/2015; DOI:10.1007/s13353-015-0309-2 · 1.48 Impact Factor
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