Coliform bacteria are the organisms that thrive in soil or vegetation and in the intestinal tract of warm-blooded animals. The presence of these bacteria indicates contamination of water and possibility of intestinal parasites or pathogens. The coliform bacteria are quite simple to identify, and may be present in much larger number. Than the more dangerous pathogen and it reacts in the same way in natural environment as other pathogens. Thus, the increase and decrease of many bacteria can be easily estimated by observing coliform bacteria.
Coliform bacteria are generally found into the runoffs from woodland, pastures, feedlots, septic tanks, sewage plants, animals and wild fowl. In this too most often, domestic animals contribute more into the bacterial pollution. Main source of coliform bacteria are the direct disposition of waste products in the water and runoff from the crowded region with high concentration of animal or human being.
There are number of sources where water is necessary like spigot, sink, and dirty containers. Another sources are reverse flow from the contaminated source, sink top carbon filter etc.
Most of the coliforms are not considered pathogens; they indicate the microbial quality of water. Most of the time coliform bacteria are tested by the public health officers to check the quality of water. Water may contain pathogens like bacteria, protozoa, and viruses that make the people sick, they are usually difficult to detect though they are present in water. Total coliforms are indicators and they grow rapidly, so they can be a means of calculating these kinds of harmful bacteria. These bacteria mostly reside in soil and water.
MPN and MUG are two approved test methods to calculate total bacteria.
MPN: (Most Probable Number) method uses a test tube full of media with a smaller inverted tube inside which it confines carbon dioxide gas released because of the growth of coliform bacteria.
MUG: this is the membrane filter method, which uses a fine porosity filter, which can retain bacteria. In this, a filter is placed on a Petri dish on a pad with growth enrichment media.