Lab 5 Coliform Bacteria and Surface Water

Topics: Coliform bacteria, Microbiology, Bacteria Pages: 6 (1041 words) Published: July 9, 2013
LAB 5: Coliform bacteria in surface waters

I. Introduction

Many organisms, including humans, have symbiotic bacteria in their guts that aid digestion. Symbiosis is an intimate relationship between different organisms in which both the host organism, e.g. the human, and the symbiote, e.g. bacteria, benefit from each other. In this case, the bacterium gets a favorable environment and food source in the intestines of a human. In return, these bacteria improve the digestibility of food through a host of enzymatic processes.

A subset of this group of bacteria is known collectively as fecal coliforms, which includes the well-known E. coli, some strains of which are necessary for human health, and some which are pathogenic and can make you very sick. Although the beneficial strains of this bacteria aid human digestion, finding these bacteria in waterways serves as a warning for the potential spread of disease because they can indicate human or animal feces. Therefore, coliform bacteria are used in water quality testing as indicators of other pathogenic bacteria that commonly are found associated with coliforms, e.g., Salmonella, Shigella, Yersinia, Klebsiella and certain strains of E. coli.

Figure 1. Breakdown of coliform into categories: total, fecal and E. coli (

Figure 1. Breakdown of coliform into categories: total, fecal and E. coli (

How do Coliforms get there? What is required is any type of mammal or bird producing excrement. This could be as simple as a duck floating on a pond or a human flushing the toilet. These single events, however, will not produce enough bacteria to be detected. What is required is some concentrated amount of waste entering the environment.

For example, Ohio does not issue Clean Water Act permits specifically for concentrated livestock operations. Ohio is the number one egg producing state, and what happens with the excrement of 30 million chickens? For the most part, these wastes are applied to agricultural fields as fertilizer, which can be extremely beneficial. What is problematic is that the state has no local control over factory farm operations and allows these farms to dump manure offsite without revealing the location under the Ohio Trade Secrecy Act. Therefore, Ohio has no control over the timing of application, the concentration of application or the distance to any waterway. Furthermore, some Ohio politicians are currently attempting to provide greater leniency by changing the legal definition of a “stream” to exclude any primary or secondary drainage channels, which connect directly to larger waterways.

Livestock operations are not all to blame. In many urban areas, storm water sewers are combined with waste water sewers in what is known as a Combined Sewer. During large rain events, the amount of water in the Combined Sewer exceeds the capacity of the waste water channel and overflow directly into streams. This is unlawful under the Clean Water Act and municipalities (including Toledo) are now required to remove these types of systems. Even in low density rural areas, faulty septic systems release coliform into waterways.

II. Lab Exercise

Today you will test the water of the Ottawa River Watershed using Petrifilm media to test for total fecal bacteria, fecal coliforms and E. coli.

Supply List

1. Ottawa River water stored in 500 mL containers| 5. (4) Petri Film Plates| 2. (4) Dixie cups for samples, RO water and waste| 6. 70% Ethanol Bottles| 3. (1) 1 ml Transfer Pipettes| 7. Ziplock Bags|

4. (1) Pipette Pump| 8. Sharpie|


1. Water will be collected for you from Ottawa River Watershed at pre-selected points.

2. Using your sharpie, label a cup with the name of one site, label a cup with the name of a second site, and label another cup “Clean Water”, for three cups total.

3. Pour approximately 10 mL of the source water into each...
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