Date of Award

Spring 1940

Document Type



Life & Environmental Sciences

First Advisor

Harry Gelsing


In 1885 Escherichia coli (Bacterium coli) was isolated from the feces of a cholera patient by Escherich. Subsequently it was found to be the normal inhabitant of the intestinal tract of humans and of many animals. Because of its presence in the excreta Escherichia coli has become important in sanitary work since it is universally accepted as an indicator of contamination with fecal material.

Specific disease germs are difficult to isolate even when present and sometimes can not be shown even when water is known to be contaminated. Fecal material is always dangerous as a source of infection and as Escherichia coli is usually present in this material it is especially well suited to distinguish between contaminated and uncontaminated material.

For this reason the presence of this organism has been chosen as an index of stream pollution. Much work has been done in this field. In such a stream as Prickly Pear Creek in Lewis and Clark County, Montana, into which the sewage of two cities empties, there is a great deal of contamination. In this thesis an attempt is made to determine what effects distance from the source of contamination, amount of organic material present, and temperature of the water, have on the number of organisms present in the sample.

Prickly Pear Creek was chosen for this work because it is a typical small stream. It has its origin in the mountains and gradually flows down through East Helena. About one-quarter of a mile below this small city the effluent from the sewage septic tank enters it. It then passes through numerous pasture lands and approximately five and a half miles from the East Helena effluent, the effluent from the Helena sewer joins the stream. The creek continues to wind through the valley until it empties into Lake Helena about eleven miles below East Helena. Lake Helena is an artificial lake formed by the back-water of Hauser Lake which in turn is formed by the damming of the Missouri River. Lake Helena greatly dilutes the contents of our stream so that the number of organisms present should be greatly reduced. Sampling points were chosen for their distance from contamination and ready accessibility.