Bacterial Nutrition

Heterotrophs

Most bacteria are like animals in that they need to consume and wide range of organic matter for their food. For this reason they are called heterotrophs. Heterotrophs are organisms that derive their nutrional requirements from complex organic substances.

They are four types of heterotrophic bacteria:

• Saprophytes (saprotrophs or saprophytic bacteria)

• Parasites (parasitic bacteria)

• Mutualists (mutualistic bacteria)

• Commensals

Saprophytes

Saprophytes feed on dead plants and animals and wastes. By doing this they cause decomposition or decay. Therefore, they are also known as decomposers. Decomposition is essential for the recycling of nutrients. Saprophytic bacteria are found in compost where they are very active. These bacteria also cause food to decay, rot and spoil.

Parasites

Parasitic bacteria feed on living bodies and living cells causing harm to the host organism. At the same time as feeding off the host they can also cause disease. When they cause disease they are called pathogens or pathogenic.

Mutualists

Mutualists feed on living organisms in partnerships with the host in such a way that both the bacterium and the host benefit. An example of these bacteria are cellulose-digesting bacteria that live in the digestive systems of herbivores (plant eaters) such as rabbits, sheep and cows.

Commensals

Commensals feed on or within living organisms but neither benefit from or harm the living organism. Examples of this type of bacteria are the many types of bacteria that live in the colon of our digestive system and on our skin.

Autotrophs (ChemoSynthetic)

Some bacteria are much like plants in the fact that they can make their own food. They are called autotrophs. Unlike plants that use energy from the Sun to make food by photosynthesis, chemosynthetic bacteria use the energy from chemical reactions, rather than the Sun, to produce organic compounds (their food). In places where sunlight is rare, such as in the deep sea, these chemosynthetic bacteria can replace plants as the source of food in food chains.