 E. coli and other facultative anaerobes constitute about 0 @.@ 1 % of gut flora , and fecal – oral transmission is the major route through which pathogenic strains of the bacterium cause disease . Cells are able to survive outside the body for a limited amount of time , which makes them potential indicator organisms to test environmental samples for fecal contamination . A growing body of research , though , has examined environmentally persistent E. coli which can survive for extended periods outside of a host . 
