How Bacteria Eat

• Unlike other organisms, bacteria do not have mouths. In fact, each bacterium contains enzymes that leave the cell to break down the compounds surrounding it so that they can be absorbed through the cell membrane. Nutrients pass through the cell membrane and are transferred into energy.
  
  

Food Sources

• Not all bacteria consume the same food. For example, most clostridium can digest carbohydrates and alcohol, but not proteins. However, some types of clostridium consume proteins when inside the human body, causing serious harm by doing so.
  
  There are species of bacteria that eat anything, ranging from sugar, corn proteins and soybean oil, to iron nails, sulfur and the compounds in wood. Common pond algae is a type of bacteria that contains chlorophyll, which makes energy from absorbing light and carbon dioxide -- this type of bacteria is called an autotroph. Other types of bacteria consume oil, and play an important role in cleaning up oil spills.
  
  

Anaerobic vs. Aerobic Bacteria

• Anaerobic bacteria do not need to consume oxygen to break down food and make energy. These bacteria are able to survive in places where there is a lack of oxygen, and therefore consume solid, often toxic, waste. Anaerobic bacteria live in pits, tanks, swamps and lagoons, for example. Comparatively, aerobic bacteria can only survive in oxygenated environments. Aerobic bacteria break down organic waste in compost heaps, or thrive in yogurt.
  
  

Importance

• Bacteria play a fundamental role in the ecology of the planet. Although some types are harmful to humans, others are very useful. For example, bacteria break down organic matter to create fertile soil for growing crops. Bacteria in water allow other lifeforms to exist, as they produce oxygen for animals living in the depths of the ocean. Plus, in warm waters the bacteria's ability to survive enables a food chain to begin, and larger forms like clams and worms to live. For humans, the controlled use of bacteria produces cheese and yogurt. "Good" bacteria in the gut aids digestion and prevents harmful bacteria from surviving.