Escherichia coli

About: Escherichia coli is a research topic. Over the lifetime, 59041 publications have been published within this topic receiving 2050337 citations. The topic is also known as: E. coli & E coli jdj.

2 Serotyping of Escherichia coli

Abstract: Publisher Summary This chapter discusses the principles and procedures for serotyping of Escherichia coli (E. coli) and discusses the morphology and immunochemistry of the surface structures that are important in serotyping. The genus Escherichia is one of the genera of tribus Escherichieae as defined in Bergey's Manual of Determinative Bacteriology. It contains one species E. coli, which consists of Gram-negative, peritrichously flagellated rods that conform to the family Enterobacteriaceae. E. coli can be differentiated from other genera in the tribus Escherichieae by indole production, the fermentation of lactose, negative reactions in KCN, gelatin, and malonate tests. E. coli is methyl red positive, Voges–Proskauer negative, and urease negative. E. coli group is heterogeneous and contains a very high number of stable subtypes. Therefore, it will be a difficult task to command all available methods in a single laboratory, if a complete typing of strains is needed.

Quorum sensing controls expression of the type III secretion gene transcription and protein secretion in enterohemorrhagic and enteropathogenic Escherichia coli

Abstract: Enterohemorrhagic Escherichia coli O157:H7 and enteropathogenic E. coli cause a characteristic histopathology in intestinal cells known as attaching and effacing. The attaching and effacing lesion is encoded by the Locus of Enterocyte Effacement (LEE) pathogenicity island, which encodes a type III secretion system, the intimin intestinal colonization factor, and the translocated intimin receptor protein that is translocated from the bacterium to the host epithelial cells. Using lacZ reporter gene fusions, we show that expression of the LEE operons encoding the type III secretion system, translocated intimin receptor, and intimin is regulated by quorum sensing in both enterohemorrhagic E. coli and enteropathogenic E. coli. The luxS gene recently shown to be responsible for production of autoinducer in the Vibrio harveyi and E. coli quorum-sensing systems is responsible for regulation of the LEE operons, as shown by the mutation and complementation of the luxS gene. Regulation of intestinal colonization factors by quorum sensing could play an important role in the pathogenesis of disease caused by these organisms. These results suggest that intestinal colonization by E. coli O157:H7, which has an unusually low infectious dose, could be induced by quorum sensing of signals produced by nonpathogenic E. coli of the normal intestinal flora.

Isolation of an Escherichia coli K-12 Mutant Strain Able To Form Biofilms on Inert Surfaces: Involvement of a New ompR Allele That Increases Curli Expression

Abstract: Many bacteria can attach to solid surfaces. The first stage of adhesion seems to be reversible: the bacteria can be removed from the surface by washing. In a second phase, bacterial multiplication and production of extracellular polymers result in the formation of a slimy layer on the colonized surface, referred to as a biofilm (15, 16). Sophisticated methods recently revealed the structural and functional organization of biofilms. Bacteria are embedded in the polymer matrix and organized in mushroom-shaped microcolonies interspersed among less dense channels in which liquid flows have been measured (14, 30; reviewed in references 5 and 6). Bacterial life in a biofilm probably involves particular gene expression. Specific patterns of expression of the laf genes of Vibrio parahaemolyticus (17) and of the algC gene of Pseudomonas aeruginosa (7, 8) have been correlated with contact of the bacteria with solid surfaces. Since microbial adhesion to solid surfaces is a very common phenomenon, biofilms develop on virtually every material that comes in contact with naturally occurring fluids, such as blood and seawater. Up to now, it has not been possible to design a nontoxic coating method able to prevent biofilm formation. Given the important medical and economical consequences of this situation, there is a strong need to understand the colonization process in order to discover a means of interfering with it. Increasing attention is being paid to the initial stages of adhesion. It is generally accepted that immersion of a clean substratum in a natural fluid is immediately followed by fast and efficient adsorption of organic molecules to the surface (33), forming a so-called “conditioning film.” Two types of bacterial interaction are then possible: weak chemical bonding between the bacterial envelope and the solid surface or the conditioning film and bridging mediated by specialized bacterial structures of adhesion. As pointed out by Marshall (16), because of strong repulsion forces, it seems unlikely that a large part of a bacterial surface could make direct contact with a solid surface. However, the contact could be consolidated by extracellular polymeric substances produced by the bacteria; these substances are subject to different colloidal interactions and could therefore form a link between the bacteria and the surface by various combinations of weak chemical bonds, dipole interactions, and hydrophobic interactions (16). The present work was undertaken to gather information on the surface colonization processes in the very well characterized Escherichia coli K-12 context. Although E. coli is the most common bacterium found in biofilms that have developed on catheters introduced into the urinary tract (12), classical laboratory strains of this species do not spontaneously stick to surfaces. However, when maintained in continuous culture for long-term experiments or industrial processes, these laboratory strains usually generate adherent mutant cells which form a thick biofilm, visible with the naked eye, on the wall of the culture vessel (9). In this paper, we report the isolation of such E. coli K-12 adherent mutants and we show that, for one of them, a point mutation affecting the regulatory properties of the OmpR protein is responsible for the biofilm-forming phenotype. The surface-binding properties of this mutant are the result of the overproduction of curli, a particular class of envelope organelles. We generalized these observations by checking the role of curli and OmpR in other adherent mutants and in clinical isolates.

Lymphoid Follicle-Dense Mucosa at the Terminal Rectum Is the Principal Site of Colonization of Enterohemorrhagic Escherichia coli O157:H7 in the Bovine Host

Abstract: Escherichia coli O157:H7 causes bloody diarrhea and potentially fatal systemic sequelae in humans. Cattle are most frequently identified as the primary source of infection, and E. coli O157:H7 generally colonizes the gastrointestinal tracts of cattle without causing disease. In this study, persistence and tropism were assessed for four different E. coli O157:H7 strains. Experimentally infected calves shed the organism for at least 14 days prior to necropsy. For the majority of these animals, as well as for a naturally colonized animal obtained from a commercial beef farm, the highest numbers of E. coli O157:H7 were found in the feces, with negative or significantly lower levels detected in lumen contents taken from the gastrointestinal tract. Detailed examination demonstrated that in these individuals the majority of tissue-associated bacteria were adherent to mucosal epithelium within a defined region extending up to 5 cm proximally from the recto-anal junction. The tissue targeted by E. coli O157:H7 was characterized by a high density of lymphoid follicles. Microcolonies of the bacterium were readily detected on the epithelium of this region by immunofluorescence microscopy. As a consequence of this specific distribution, E. coli O157:H7 was present predominately on the surface of the fecal stool. In contrast, other E. coli serotypes were present at consistent levels throughout the large intestine and were equally distributed in the stool. This is a novel tropism that may enhance dissemination both between animals and from animals to humans. The accessibility of this site may facilitate simple intervention strategies.

Microbial competition: Escherichia coli mutants that take over stationary phase cultures

Abstract: Many microorganisms, including Escherichia coli, can survive extended periods of starvation. The properties of cells that survived prolonged incubation in stationary phase were studied by mixture of 10-day-old (aged) cultures with 1-day-old (young) cultures of the same strain of Escherichia coli. Mutants from the aged cultures that could grow eventually took over the population, which resulted in the death of the cells from the young cultures. This phenotype was conferred by mutations in rpoS, which encodes a putative stationary phase-specific sigma factor. These rapid population shifts have implications for the studies of microbial evolution and ecology.