Wednesday, 30 May 2012

Genetics and Bacterial Resistance


By Megan Saunders

Bacteria have many mechanisms for adapting to their environment and they certainly use them when responding to adverse conditions. In particular, bacteria such as Eschericha coli go through many genetic mutations when building resistance to various antibiotics (Toprak et al. 2012). A team of scientists at Harvard have developed a method for recording and understanding these mutations in an experiment which could have future implications on the way we approach bacterial infections (stealth tactics of bacteria revealed, 2012).

aims to not only record, but understand precisely how bacteria forms a resistance to antibiotics. In order to control the present antibiotic, the concentration of that drug and to record how the bacterium responds, they created the ‘morbidostat’ (stealth tactics of bacteria revealed, 2012). Results have been obtained from E. coli as it was monitored about how it responded to controlled doses of various antibiotics.



The results showed that the bacteria developed resistance to all three of the introduced antibiotics (stealth tactics of bacteria revealed, 2012). Some antibiotics can be faulted by a single gene change, although in this case, like many others, a number of genetic mutations had to occur to obtain the desired phenotype (Toprak et al. 2012). The group of genetic mutations that occurred in this case targeted the bacteria’s susceptibility to each of the antibiotics. The way in which the bacteria responded to the three test drugs separately was a testament to the variability bacteria is capable of. Achaean organisms are widely recognized for their adaptive abilities, which stem from their methods of reproduction. High generational rates are achieved by the ability of the organisms to use binary fission.  Also, plasmids play a role in increasing the genetic material available to the bacteria (Campbell et al. 2009). These mechanisms give reason for the successful rapid mutation of genes measured within the experiment.

The mutations occurring within the bacteria differed between the types of antibiotic it was exposed to (Toprak et al. 2012). The differences between these changes can be applied to the way the bacteria’s resistance developed. But perhaps the most useful data that resulted from this experiment was the congruency between separated test populations.  The genomes of bacteria responding to the same drug, which were measured throughout the test, concluded that “parallel populations evolved similar mutations and acquired them in a similar order.” (Toprak et al. 2012, p101). The patterns that were observed suggests that there are specific pathways of mutation, along which bacteria moved to achieve a goal; antibiotic resistance (Toprak et al. 2012). Now that these genetic pathways have been measured, a more complex set of knowledge can be applied to improving antibiotics and increasing their effectiveness in the future.

A greater understanding of bacteria and it’s mechanisms for coping with its environment is being achieved through many studies being conducted, genetic resistance is a particularly relevant topic and developing improved ways of treating bacterial infections in humans is highly beneficial. The measurement of the response of bacteria to antibiotics has resulted in evidence of mutational pathways for bacteria gaining resistance (Toprak et al. 2012). These results are of great significance to the notions of improving the antibiotic method and overcoming bacterial resistance.

References
 ‘Stealth tactics of bacteria revealed’, 2012, New Scientist, issue 2844 <http://www.newscientist.com/article/mg21228443.300-stealth-tactics-of-bacteria-revealed.html>
E. Toprak, A. Verdes, J.B. Michel, R. Chait, D.L. Hartl, R. Kishony, Evolutionary paths to antibiotic resistance under dynamically sustained drug selection, research publication, Nature America, volume 4 <http://kishony.med.harvard.edu/>
Campbell, Reece, Meyers, 2009, Biology, 8th edn, Pearsons


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