What are coliforms?

Hint: Coliforms are a type of bacteria. These organisms are generally harmless to the organisms or hosts they are present in. However, presence of coliforms indicates the sanitary conditions of consumable foods and water.

Complete answer:
Coliform bacteria are rod-shaped bacteria that stain negative with Gram stain. They are present in large concentrations in the environment and also in the intestine and feces of all warm-blooded animals. They are spore forming bacteria and can ferment lactose.
The coliforms are divided into three groups: Total coliforms, Faecal coliform and E. coli.
Total coliforms are bacteria present in water, soil as well as in the intestines of animals and their faecal matter. These harmless organisms are considered to be indicators of sanitary conditions of water. However, presence of total coliforms does not mandatorily indicate presence of harmful microorganisms in the water.
Faecal coliforms are a subtype of total coliforms. They are found mostly in the intestines of thermoregulators and hence, in their faecal matter. Presence of these bacteria in water or food indicate its contamination by either sewage or faecal matter. Faecal coliforms can be both pathogenic and non-pathogenic. They are not capable of surviving outside the host body.
Escherichia Coli are restricted to the intestines of animals. They carry out their life cycle in the body of the hosts. E. coli, if present in drinking water indicates that the water has been contaminated in the recent past and requires treatment before consumption. In general, E. coli are harmless bacteria. However, certain strains can cause serious ailments like diarrhoea, vomiting, fever or respiratory troubles.
There are laboratory techniques to find out, determine and confirm the concentration of coliforms in consumable food and water. If it is found to be contaminated, proper treatment procedures are undertaken.

Note: Coliform bacteria are spore forming, rod-shaped bacteria present in the environment and the intestine of warm-blooded animals. These bacteria are generally used as indicator species while determining the consumable state of consumable water and sometimes food. Though coliforms themselves are primarily harmless, their presence indicates the presence of other pathogenic microorganisms.