BIOLOGY 7A

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 Organization (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
• those that inhibit nucleic acid synthesis. 

For  example, penicillin and its related compounds prevent susceptible  bacteria from creating a cell wall. They do this 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?

Apart from direct transfer from parent to daughter  cell through cellular reproduction, 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.

• Write  a sentence for each of these mechanisms of horizontal gene transfer in  bacteria, 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

Discussion Requirements

Your Discussion should be at least 300 words in length.

Use  APA citations and references for the textbook and any other sources  used; you should use at least 1 APA citation and reference, but you can  use more if needed.