Reference no: EM132537501

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. For example, penicillin and its related compounds prevent susceptible bacteria from creating a cell wall. This was done by binding to and inactivating an enzyme (transpeptidase) necessary for the cross-linking of peptidoglycan in the wall, thus stopping its formation. Resistance to this antibiotic is due to the bacteria producing its own enzyme called beta-lactamase which breaks the ring structure of the penicillin and prevents its ability to bind to the bacterial transpeptidase.

As with all proteins, beta-lactamase is encoded by a section of DNA - but how does that DNA and the ability to produce a new protein transfer from one population of bacteria that have resistance to another population that don't?

Other than direct transfer from parent to daughter cell, horizontal transmission of DNA between different genomes also occurs. Horizontal gene transfer is made possible by the existence of mobile genetic elements, such as plasmids (extrachromosomal genetic material), transposons ("jumping genes") and bacteria-infecting viruses (bacteriophages). These elements are transferred between organisms through different mechanisms, which in prokaryotes include transformation, conjugation, and transduction.

• Give sample sentence for each of these mechanisms describing the manner in which the DNA can be transferred from one cell to another.
• 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.
• Finally, discuss the danger that antibiotic resistance poses in today's society, consider how man has contributed to this and suggest any strategies that you think may be able to halt it or prevent its expansion