Antibiotics are used to treat a wide variety of bacterial infections and have saved millions of lives since they were first introduced in the 1940s and 1950s. However, due to both overuse and misuse, many are no longer effective and The World Health Organisation (WHO) considers the emergence of new antibiotic-resistant bacteria to be a serious threat to global public health. According to their mechanism of action, antibiotics can be divided into three main groups, those inhibiting cell wall synthesis, those inhibiting protein synthesis and those that inhibit nucleic acid synthesis. Choose a disease or an organism that has a well-documented mechanism of resistance (such as methicillin resistant Staphylococcus aureus - MRSA or tuberculosis) and see if you can identify the gene or genes that confer resistance and the method of DNA transfer thought to contribute to its spread. This may be from one organism to another or may simply be passed down from mother to daughter cell due to environmental pressure.