Friend or Foe

Friend

Many bacteria are useful or beneficial to humans and can be used in:

• composting

• treating sewage

• food production

Composting

Bacteria are decomposers. Without them nutrients could not be recycled when organisms die, and dead organisms could not be broken down, decay and rot. You would not be able to buy a bag of compost from a garden centre or have your own compost bin with out these bacteria.

Sewage treatment

We have exploited this further when we treat waste faeces and urine at sewage treatment plants. Some bacteria can break down waste that even includes some harmful microbes that might be present. This is very important as there can be some really nasty pathogens present in faeces that can cause diseases such as cholera and typhoid.

Food Production

Bacteria are used in the manufacture of yoghurt, cheeses and other fermented foods.

Lactobacillus bulgaris, Lactobacillus acidophilus, and Streptococcus thermophilus are just three species of bacteria used to make live yoghurt. Yoghurt is just fermented milk. A mixture of bacteria are added to milk to make a started culture which is then used to make yoghurt.

The manufacture of cheese also relies on bacteria. Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. lactis are two lactic acid bacteria used to make Cheddar cheese. Streptococcus salivarius ssp. thermophilus is used to make cheeses such as Italian mozzarella cheese. Whilst Lactobacillus helveticus is often used to make Swiss and Dutch cheeses such as Gruyere and Gouda.

Other fermented foods such as Kombucha and Kefir rely on bacteria along with the fungus yeast for the fermentation process.

Pharmaceuticals, such as Genetically Engineered Human Insulin

Bacteria and recombinant DNA technology is used to make human insulin. Scientists use special enzymes to cut out the human insulin gene from human cells. They use a second enzyme to cut open the bacterial plasmid DNA in a harmless strain of E. coli, and then used a third enzyme to insert the human insulin gene into the bacterial plasmid DNA. When the bacteria reproduce rapidly by binary fission, they produce human insulin, which can then be extracted, purified and used to treat diabetes.

FOE

Despite their many benefits, bacteria can also be harmful. They cause:

• food spoilage

• food poisoning

• Diseases

• antibiotic resistance

Food spoilage

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Food poisoning

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Diseases

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Antibiotic Resistance

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