B6 - Antibiotics and Useful Bacteria Flashcards
What did Louis Pasteur do?
A French scientist called Louis Pasteur (1822–95) proved that decay was caused by microorganisms in the air. He went on to explain that microbes entering the body would cause disease. He proposed the idea that if we could stop microbes entering the body, we could prevent illness. These ideas are known as the germ theory.
What did Joseph Lister do?
Armed with the knowledge that microbes entering the body caused illness, Joseph Lister (1827–1912) developed the idea of antiseptics. These are solutions that kill microbes. Lister was a surgeon, and he sprayed his instruments with a solution of carbolic acid. This killed microbes on the instruments, which greatly reduced the number of postoperative infections.
What did Alexander Fleming do?
Alexander Fleming (1881–1955) worked in St Mary’s Hospital in London. He discovered that a mould called penicillin produced a chemical that would kill bacteria. The fungus grew on one of his agar plates of bacteria. It caused an area where the bacteria could not grow, as they were killed by the penicillin.
During the Second World War scientists were able to make sufficient penicillin to give to a patient, and the patient recovered from the illness. Penicillin was the drug that killed bacteria – the first antibiotic.
Why can antibiotics not cure all infections?
• Antibiotics do not kill viruses. This is because viruses do not feed, and do not have a cell structure to damage. These
are the two main ways that antibiotics work on bacteria.
• Some bacteria can develop resistance to an antibiotic, and the drug no longer works on them.
How do bacteria develop resistance?
• A mutation occurs in some bacteria, which gives them
resistance to the antibiotic.
• Treatment by the antibiotic kills the bacteria in the population that do not have this mutation, so are not resistant.
• The bacteria with the resistance survive.
• The surviving bacteria reproduce, passing the resistance gene on.
• Eventually, the whole population becomes resistant.
How have doctors changed their use of antibiotics over the years?
- Doctors only prescribe antibiotics when really necessary. They do not use them for viral conditions or minor illnesses. This reduces the chance of antibiotic- resistant bacteria becoming the most common strain.
- Patients are encouraged to complete the course of any antibiotics that they are given. This way all the microbes should be killed before resistance can fully develop.
How are bacteria used in the making of yoghurt?
Yoghurt is made by adding the bacterium Lactobacillus to milk. It is a very nutritious food which is rich in protein, calcium, and vitamins.
How is bacteria used in the making of vinegar ?
It is produced by the acidifying of wine, cider, or beer to produce wine, cider, and malt vinegars. The production of vinegar uses bacteria such as Acetobacter.
How is bacteria used in the making of cheese?
Cheese is made by causing milk to curdle, or separate into a solid curd and liquid whey. Curdling can be achieved using a mix of enzymes and bacteria such as Lactobacillus. The solid part of the milk is then turned into cheese. Like yoghurt, cheese is rich in protein, calcium, and vitamins
How is bacteria used in the making of silage?
Silage: a common winter fodder for cattle. Green cut vegetation is piled up in a large heap and covered in plastic, or placed in a silo. The vegetation is broken down by fermentation, or anaerobic respiration. The process will occur naturally, but it is speeded up by adding another Lactobacillus species.
How is bacteria used for composting?
The dead remains of plants and animals are digested by bacteria and fungi to form nutrient-rich soils. Often the remains are simply piled up at the end of the harvest and allowed to rot down until the next planting season.
How is yoghurt made?
- Milk is pasteurised by heating to 71.2°C for 15-20 seconds to kill 99% of the bacteria in it.
- Incubation : the bacteria multiply using the milk as a food source
- The Lactobacillus bacteria break down the milk sugar ( lactose ) into lactic acid. This converts the milk into yoghurt.
- A sample of the yoghurt is taken for quality control and to add to the next batch.
- Bacteria in the sample from the previous batch are added which leads to step 2.
- Following on directly after step 3, the colours and flavours are added, and the product is marketed.
