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.

Lysogeny and transformation in mycobacteria: stable expression of foreign genes

Abstract: Requisite to a detailed understanding of the molecular basis of bacterial pathogenesis is a genetic system that allows for the transfer, mutation, and expression of specific genes. Because of the continuing importance of tuberculosis and leprosy worldwide, we initiated studies to develop a genetic system in mycobacteria and here report the use of two complementary strategies to introduce and express selectable genetic markers. First, an Escherichia coli cosmid was inserted into the temperate mycobacteriophage L1, generating shuttle phasmids replicating as plasmids in E. coli and phage capable of lysogenizing the mycobacterial host. These temperate shuttle phasmids form turbid plaques on Mycobacterium smegmatis and, upon lysogenization, confer resistance to superinfection and integrate within the mycobacterial chromosome. When an L1 shuttle phasmid containing a cloned gene conferring kanamycin resistance in E. coli was introduced into M. smegmatis, stable kanamycin-resistant colonies--i.e., lysogens--were obtained. Second, to develop a plasmid transformation system in mycobacteria, M. fortuitum/E. coli hybrid plasmids containing mycobacterial and E. coli replicons and a kanamycin-resistance gene were constructed. When introduced into M. smegmatis or BCG (Mycobacterium tuberculosis typus bovinus var. Bacille-Calmette-Guerin) by electroporation, these shuttle plasmids conferred stable kanamycin resistance upon transformants. These systems should facilitate genetic analyses of mycobacterial pathogenesis and the development of recombinant mycobacterial vaccines.

Programmable bacteria detect and record an environmental signal in the mammalian gut.

Abstract: The mammalian gut is a dynamic community of symbiotic microbes that interact with the host to impact health, disease, and metabolism. We constructed engineered bacteria that survive in the mammalian gut and sense, remember, and report on their experiences. Based on previous genetic memory systems, we constructed a two-part system with a “trigger element” in which the lambda Cro gene is transcribed from a tetracycline-inducible promoter, and a “memory element” derived from the cI/Cro region of phage lambda. The memory element has an extremely stable cI state and a Cro state that is stable for many cell divisions. When Escherichia coli bearing the memory system are administered to mice treated with anhydrotetracycline, the recovered bacteria all have switched to the Cro state, whereas those administered to untreated mice remain in the cI state. The trigger and memory elements were transferred from E. coli K12 to a newly isolated murine E. coli strain; the stability and switching properties of the memory element were essentially identical in vitro and during passage through mice, but the engineered murine E. coli was more stably established in the mouse gut. This work lays a foundation for the use of synthetic genetic circuits as monitoring systems in complex, ill-defined environments, and may lead to the development of living diagnostics and therapeutics.

Outer membrane protein A of Escherichia coli contributes to invasion of brain microvascular endothelial cells.

Abstract: Escherichia coli is the most common gram-negative bacteria causing meningitis during the neonatal period, but is unclear what microbial factors mediate traversal of E. coli across the blood-brain barrier. Outer membrane protein A (OmpA), a highly conserved 35-kDa protein, was examined for its role in E. coli K1 invasion of brain microvascular endothelial cells (BMEC). The invasive capability of the OmpA+ strains was 25- to 50-fold greater than that of OmpA- strains, and the invasive capability of OmpA- strains was restored to the level of the OmpA+ strain by complementation with the OmpA+ E. coli into BMEC. Two short synthetic peptides (a hexamer, Asn-27-Glu-32, and a pentamer, Gly-65-Asn-69) generated from the N-terminal amino acid sequence of OmpA exhibited significant inhibition of OmpA+ E. coli invasion, suggesting that these two sequences represent the OmpA domains involved in E. coli invasion of BMEC. These findings suggest that OmpA is the first microbial structure identified to enhance E. coli invasion of BMEC, an important event in the pathogenesis of E. coli meningitis.

Characterization of enteroadherent-aggregative Escherichia coli, a putative agent of diarrheal disease.

Abstract: Escherichia coli that exhibit the aggregative pattern of adherence to HEp-2 cells (enteroadherent-aggregative E. coli [EA-AggEC]) have been epidemiologically incriminated as a cause of diarrhea. We undertook a preliminary microbiological and pathogenetic characterization of 42 isolates of this putative pathogen. The strains were negative by tests with DNA probes for enteropathogenic, enterotoxigenic, enteroinvasive, and enterohemorrhagic E. coli and, by serotype, did not fit these categories. Thirty-nine of 42 strains had a 55-65-megadalton plasmid; many shared DNA homology. With one representative strain, plasmid transfer was accompanied by transfer of smooth lipopolysaccharide, fimbriae expression, and the aggregative property. EA-AggEC caused characteristic lesions in rabbit and rat ileal loops. The intestinal lesions and (Shiga-like) limb paralysis and death in rabbits inoculated with live organisms suggest toxin involvement; assays for Shiga-like toxins were negative. These preliminary results support the contention that EA-AggEC may represent a distinct category of diarrheagenic E. coli.

Prevention of Colonization of the Urinary Tract of Mice with Escherichia coli by Blocking of Bacterial Adherence with Methyl α-d-Mannopyranoside

Abstract: Methyl alpha-D-mannopyranoside (alpha MM), a competitor inhibitor of the binding of mannose by Escherichia coli, was tested for its ability to prevent infection of the urinary tract of mice with infective strains of the organisms. Injection of the bacteria in the presence of the drug resulted in a considerable reduction in the number of bacteriuric mice. In this system alpha MM was inactive against Proteus mirabilis in accordance with its inability to inhibit the adherence of this organism to epithelial cells in vitro, and methyl alpha-D-glucopyranoside proved inactive against both E. coli and P. mirabilis.