Solution:

• Coliforms are bacteria that are always present in the digestive tracts of animals, including humans, and are found in their wastes. They are also found in plant and soil material.

• Staphylococcus bacterium is a member of the microbiota of the body, found in the upper respiratory tract and on the skin.

• Salmonella lives in the intestinal tracts of animals and birds and is transmitted to humans by contaminated foods of animal origin.

• Sulfur bacteria are found in the anoxic layer of their habitat, which promots the growth of many heterotrophic organisms by supplying inorganic nutrients to the above oxic layer.