Antibiotic resistance of bacteria:
Bacteria can survive in the presence of an antibiotic.
- Many diseases caused by bacteria can be treated with penicillin and other antibiotics.But after the Second World War, the use of antibiotics became widespread, many bacteria developed resistance.
- Staphylococcus aureus is a common bacterium found thatlives on the skin.
- They are harmless but can invade the bloodstream - infect tissues in the kidney or bones and become fatal.
There are straints of Saureus which are resistant to antibiotics.
- This resistance is probably caused by spontaneous mutation.
- This means the bacterium procudes an enzyme that can break down penicillin.
If the bacteria is exposed to penicillin the ones without resistance will be killed, but the bacteria with resistance will survive and due to lack of competition, grow rapidly.
Antibiotic resistance is more likely to occur when a small dose of antibiotics is used for a short time.
- It will kill some of the bacteria but not all and may lead to do bacteria having some resistance.
- This means the next time they are used the bacteria is less vulberable and some more of them may survive.
*repeated use of small doses of antibiotics can produce very resistant strains.
- do not work against viral diseases
- This leads to strains of antibiotic-resistant bacteria being disovered in the guts of these animals.
- Bacteria may pass on the resitant gene to other bacteria. This makes harmless bacteria living in our gut have the have the ability to pass on this resistance to pathogenic bacteria.
- Biston betularia (peppered moth) is found near Manchester, England and elsewhere in the UK.
- Before 1848, trees were covered with off-white lichen.
- The moths were speckled and therefore camoflauged from birds when resting on trees. Occasionally a black moth would appear.
- Due to the coal based industry, trees became covered in soot and white moths were easily spotted and eaten.
- The dark (melanic) form now had the advantage and became predominant in certain areas.
Drafted by Venetia (Biology)