The CORRECT way to write E. coli is:
E. coli
Note the following:
•The uppercase "E" and the lowercase "coli" in E. coli
•The dot (period, full stop) after the "E" in E. coli
•The single space after the dot in E. coli
•E. coli should be in italics
INCORRECT ways to write E. coli are:
•E. coli (incorrect because it is not in italics)
•E.coli (incorrect because there is no space after the dot)
•E. Coli (incorrect because of uppercase "C")
•E. COLI (incorrect because of uppercase "COLI")
•e. coli (incorrect because of lowercase "e")
•E.-coli (incorrect because hyphen used instead of a space)
Please note in particular:
•Always use italics to write E. coli
•Always use a single space after the dot (i.e. before "coli") in E. coli
•Always use an uppercase "E" in E. coli
•Always use lowercase "coli" in E. coli
•Never use an uppercase "C" in E. coli, not even in headlines or headings
•Never use uppercase COLI in E. coli, not even in headlines or headings
•Never use a hyphen in E. coli
To be absolutely correct:
•Write Escherichia coli the first time you refer to the microbe in your report, article, or story
•Everywhere else in the same report, article, or story use the abbreviated form: E. coli