Microorganisms are of great significance to foods the reasons: microorganisms can cause spoilage of foods, microorganisms are used to manufacture a wide variety of food products, and microbial diseases can be transmitted by foods. The cycling of nutrients such as carbon, nitrogen, and sulfur is completed by their ceaseless labor. Organic carbon, in the form of dead and rotting organisms, would quickly deplete the carbon dioxide in the atmosphere if not for the activity of decomposers. Each human body hosts 10 microorganisms for every human cell, and these microbes contribute to digestion, produce vitamin K, promote development of the immune system, and detoxify harmful chemicals. Bacteria can live in hotter and colder temperatures than humans, but they do best in a warm, moist, protein-rich environment that is pH neutral or slightly acidic. There are exceptions, however. Some bacteria thrive in extreme heat or cold, while others can survive under highly acidic or extremely salty conditions. Spoilage microorganisms are those that can grow in a food and cause undesirable changes in flavor, consistency color, or appearance. Also bacterial enzymes may affect slow deterioration of frozen or dried foods during long-time storage.

Bacteria break down (or decompose) dead organisms, animal waste, and plant litter to obtain nutrients. But microbes don't just eat nature's waste, they recycle it. The process of decomposition releases chemicals (such as carbon, nitrogen, and phosphorus) that can be used to build new plants and animals. They decompose dead and decaying matter from plants and animals, convert them into simpler substances that are later used up by other plants and animals. Thus, they are used to breakdown harmful substances. You might not realize it, but bacteria is used in many agricultural and environmental industries. Most significantly, bacteria is used to help clean up oil spills, nuclear waste, and is also able to detect pollution and break down sewage.

The microbial groups associated with foods are bacteria, fungi, protozoa, algae, and viruses. Microbial genetics has important applications in molecular and cell biology, medicine, agriculture, and the food and pharmaceutical industries. Bacteria are important in sewage treatment and the breakdown of oil spills, the production of cheese and yogurt through fermentation, the recovery of gold, palladium, copper and other metals in the mining sector, as well as in biotechnology, and the manufacture of antibiotics and other chemicals. Environmental conditions can affect microbial growth? Temperature, oxygen, pH, water activity, pressure, radiation, and lack of nutrients, these are the primary ones. One of the famous names among bacteria which are helpful for the environment is Rhizobium. These bacteria are also known as nitrogen-fixing bacteria. They are present in the root nodules of plants and fix the nitrogen present in the atmosphere. They are considered to be very helpful to the environment. Within food plant cropping systems, microorganisms provide vital functions and ecosystem services, such as biological pest and disease control, promotion of plant growth and crop quality, and biodegradation of organic matter and pollutants.