What does colicin mean?
A colicin is a protein-based toxin manufactured by certain bacteria, most famously strains of Escherichia coli, that kills or suppresses the growth of rival bacteria, typically those closely related to the producing organism. Each colicin is encoded on a plasmid, and the producer protects itself by pairing the toxin with an immunity protein. First identified in the 1920s, colicins became foundational tools in molecular biology: studying them revealed how proteins traverse membranes and helped inspire later work on antibiotics. In scientific writing the term appears chiefly in microbiology and biochemistry, often in phrases such as 'colicin-producing strain' or 'colicin receptor', and specific varieties are labelled with letters, such as colicin E1. Though obscure outside the laboratory, the word carries real historical weight, marking one of the earliest examples of what biologists now call bacteriocins — nature's narrow-spectrum microbial weapons.
nounA proteinaceous toxin produced by certain strains of bacteria such as Escherichia coli that kills or inhibits the growth of other, often closely related, bacterial strains.
- Any of a group of plasmid-encoded protein antibiotics produced by strains of Enterobacteriaceae, especially E. coli, that are toxic to closely related bacteria but harmless to the producing strain, which carries immunity proteins.
"The strain secreted a colicin that wiped out competing bacteria on the agar plate."
"Researchers purified the colicin and tested its lethal effect against sensitive laboratory strains."
"Because the pathogen carried no resistance to the colicin produced by the probiotic strain, it was rapidly eliminated from the culture."
Regular plural; standard in scientific literature when referring to multiple colicins or the family of these toxins collectively.
"Several distinct colicins were screened for activity against the resistant isolate."
Discovered nearly a century ago, colicins were among the first bacterial weapons scientists ever characterized — and they helped launch modern research into how proteins cross cell membranes.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of colicin
The word 'colicin' was coined in the mid-20th century (the older spelling 'colicine' also appears in early literature) from the species name of its source bacterium, Escherichia coli, combined with the suffix '-in' conventionally used for proteins. The name 'Escherichia' honours the German paediatrician Theodor Escherich, who described the bacterium in the 1880s, while 'coli' reflects its habitat, the colon. Related terms built on the same root include 'colitis', 'colonic', and the broader class name 'bacteriocin'.
How colicin is actually used
Strictly a technical term used in microbiology, genetics, and biochemistry; it does not appear in everyday speech. The plural 'colicins' is common in scientific literature, where individual members are often designated by letters (e.g., colicin E1, colicin M) or by their producer strain.
Easily confused with colicin
Colic refers to severe abdominal pain, whereas a colicin is a bacterial protein toxin.
'Cholic' relates to bile or gall (as in cholic acid), while 'colicin' is a bacterial toxin whose name derives from E. coli.