## Introduction Escherichia coli, commonly called E. coli, is a versatile bacterial species that inhabits the intestines of humans and animals. Many strains are benign and contribute to digestion, vitamin K synthesis, and colonization resistance, while others cause significant disease. This article summarizes E. coli’s biology, clinical relevance, and role in gut microbiome testing. ## Brief history and model organism status Discovered in 1885 by Theodor Escherich, E. coli was formally named in his honor in 1919. Over the 20th century it became a laboratory workhorse; non-pathogenic strains such as K-12 are foundational in molecular biology and genetic engineering. ## Biology and classification E. coli is a Gram-negative, rod-shaped, facultative anaerobe in the Enterobacteriaceae family. Its genome is plastic, enabling rapid acquisition of virulence or antibiotic-resistance genes via plasmids, phages, and horizontal transfer. This genetic adaptability explains why both commensal and pathogenic variants coexist. ## Pathogenic vs. commensal strains Pathogenic E. coli fall into defined pathotypes: enterohemorrhagic E. coli (EHEC, e.g., O157:H7) can cause bloody diarrhea and hemolytic uremic syndrome; enterotoxigenic E. coli (ETEC) is a common cause of traveler's diarrhea; uropathogenic E. coli (UPEC) is the primary agent of urinary tract infections. Commensal strains like Nissle 1917 are used as probiotics and in research. ## Role in gut microbiome testing Modern sequencing-based gut microbiome tests frequently report E. coli abundance. Elevated E. coli signals may reflect dysbiosis, recent antibiotic use, or enrichment of pathogenic strains, but interpretation must consider clinical context and other taxa. Consumers and clinicians receive different report formats and interpretations; for detailed comparisons see this technical overview: Gut microbiome testing: consumers and professionals. ## Engineered strains and therapeutic potential Synthetic biology is repurposing E. coli as a delivery vehicle for therapeutics. Engineered strains that produce anti-inflammatory proteins or sense intestinal conditions are in research pipelines. These approaches aim to modulate the microbiome in situ while minimizing systemic exposure. ## Environmental survival and biofilms E. coli can form biofilms—aggregated communities embedded in extracellular matrix—on surfaces such as pipes and catheters. Biofilms protect cells from disinfectants and facilitate persistence in environmental reservoirs, contributing to outbreak risk. ## Diet, disease links, and public health Diet influences E. coli population dynamics: diets high in red and processed meats may favor certain pathobionts, while fiber-rich and polyphenol-rich diets tend to support beneficial commensals. Foodborne outbreaks from contaminated produce, meat, or water underscore the importance of surveillance, traceback, and hygiene in prevention. ## Practical context and resources For research connecting gut microbes to exercise performance, see this related review: Gut microbiome and endurance sports. For a product reference, a placeholder resource is microbiome test product. ## Conclusion E. coli illustrates the dual nature of many microbes: beneficial in many contexts, harmful in others. Accurate interpretation of test results and ongoing research into engineered and therapeutic strains will shape how clinicians and consumers understand this species in the coming years. For a comprehensive overview, read the full InnerBuddies guide: [comprehensive InnerBuddies guide on E. coli](https://www.innerbuddies.com/blogs/gut-health/everything-about-e-coli).