Escherichia coli are a gram positive bacterium found in the human digestive system

Escherichia coli are a gram positive bacterium found in the human digestive system (Ryan, K. & Ray, G., 2004, p 22). They are rod shaped and mostly found in the colon of mammals. They are considered to be harmless to the host but could at times cause food poisoning which may result into diarrhea. They are microscopic organisms and cannot be viewed by naked eyes. As for Bacillus stearothermophilus, these are gram positive bacteria that exist in temperatures varying at around 30- 70°C. They are mostly found in the soil. In case they infiltrate food staffs, the cause rotting thus being harmful to other living organisms for instance humans. They too are rod shaped and microscopic in nature.