The role of bacteria in recycling minerals through ecosystems
Many bacteria are de-composers. When organisms die, these bacteria break down the complex molecules that are found in the bodies of the dead organisms into much simpler molecules. Th bacteria use some of these for their own metabolism, but in the process they release some minerals, in various forms, into the environment. Many elements are recycled in this way, including:
• carbon
• nitrogen
• sulfur
• phosphorus
The nitrogen cycle
Th element nitrogen is found in many important organic molecules in all living organisms. These include: proteins, DNA, RNA, ATP and many others.
It is important that once organisms die, the nitrogen they contain is made available again to other organisms. Several different types of bacteria are involved in this recycling of nitrogen.
The sulfur cycle
Sulfur is found in fewer types of organic molecule than nitrogen, but it is found in many proteins.
If the populations of bacteria that are involved in the nitrogen cycle and the sulfur cycle were reduced, then the cycling of these elements could not occur, and all life would be impossible as a result. It is worth thinking about. We are made from atoms and molecules that have been in many other bodies before they were in ours. Th micro-organisms that recycle carbon, nitrogen, sulfur and all the other minerals make them available again … and again … and again …
How are bacteria used in industrial processes?
Bacteria and other micro-organisms have been used in manufacturing processes for thousands of years. Thy have been used to make bread, alcohol, yogurt, vinegar as well as many other products. They have also been used in key processes such as sewage treatment.
Production of vinegar
Vinegar is a dilute solution of ethanoic acid in water. It also contains other substances that give the vinegar its flavor. Vinegar is used in two main ways: to flavor foods and to preserve foods
Vinegar is too acidic for most micro-organisms to grow and multiply, so keeping foods in vinegar is a good way of preserving them. We call this method of preserving food pickling. Vinegar is produced by fermenting beer, wine or cider for a second time. A culture of a special bacterium called Acetobacter is used. Th alcohol in the beer, wine or cider is oxidized to ethanoic acid. This takes place in a special fermenter. Th fermenter is filed with wood shavings and the alcohol source is sprayed in from the top. It trickles down through the wood shavings, which are covered with
Acetobacter bacteria. As the liquid flows past them, the bacteria oxidize the alcohol to ethanoic acid. Air is blown in at the bottom to supply the oxygen the bacteria need. Th vinegar drips out at the bottom of the wood shavings and is tapped off
This type of production is called continuous production, as alcohol is continuously being fed in and ethanoic acid is continuously dripping out at the bottom of the fermenter.
Producing antibiotics
The fist antibiotics all came from fungi. Today, they are increasingly being made using genetically modified bacteria in huge fermenters.
Genetically modified bacteria are also used to produce:
• insulin
• human growth hormone
• antibiotics
• enzymes for washing powders
• human vaccines, such as the vaccine against hepatitis B
Sewage treatment
All types of sewage treatment rely on the action of a range of microorganisms to oxidize the organic matter present in sewage. There are two main methods:
• the percolating filter method
• the activated sludge method
In the percolating filter method:
• sewage is screened to remove large pieces of debris
• it stands in a large settlement tank to allow suspended matter to settle out
• it is then allowed to trickle through a bed of stones, each of which is covered in a layer of micro-organisms (bacteria, fungi and protozoa)
• as the sewage trickles through the filter bed, the microorganisms digest the organic matter and absorb the products
• by the time the liquid reaches the bottom of the filter bed, the polluting organic matter has all been removed
In the activated sludge method:
• sewage is screened and allowed to stand in settlement tanks, as in the percolating filter method
• it is then pumped into treatment tanks, where: – activated sludge, rich in micro-organisms, is added – oxygen is blown through the mixture
• in the oxygenated mixture, the micro-organisms from the added activated sludge oxidize the polluting organic matter, reproducing as they do so
• some of the sludge formed is recycled to ‘seed’ new tanks.