Tuesday, 23 June 2015

Bacteria – The Next Frontier

*This is an image that I prepared and took myself of what was supposed to be a biofilm of E.coli. The big bubble in the middle is just an air bubble, however, all the green stuff around it are bacteria that light up green when they are in blue light.*
Microbiology (in my opinion) has been an area of science that has been overlooked since the start of the Human Genome Project and the resulting modern age of molecular biology. This is a great shame; scientists have awkwardly ignored microbiology (like the weird kid in school) and this has now bitten us in the arse as we need help fighting the battle against antibiotic resistant bacteria. Bacteria are the largest kingdom in the tree of life and scientists don’t know what most of the bacteria look like or even do. Ignoring bacteria and not putting enough effort into studying bacteria have now lead to a ‘global antibiotic crisis’. However, in the last few years, microbiology has again been looked too, and there are some interesting new developments that might help us in this battle.

So first off I want to explain a bit more about what the antibiotic crisis actually is. Since the discovery of penicillin in 1928, bacterial infections have been treated by using a certain amount of an antibiotic for a certain number of days. This kills 99%* of the bacteria helping the immune system clear the rest from the body (note antibiotics only work on bacteria, NOT viruses!).  Even though there are a huge number of bacteria species that infect us, there are only a handful of different antibiotics used to treat all of them. The antibiotics used today target a number of similar characteristics that all the common bacteria share, for example making a cell wall. But this is problem number one; not all bacteria do the same so some antibiotics don’t work, also almost all antibiotics target growing bacteria, however in biofilms (see my earlier post http://lifeinbiomed.blogspot.co.uk/2015/05/the-science-behind-cocowhite-and.html) the bacteria don’t grow = the antibiotics don’t work.
The other MAJOR problem with antibiotics is that they provide a selection pressure on the bacteria. What I mean by this is that when you use antibiotics it will kill 99% of the bacteria, however, 1% of the bacteria will remain alive because of natural differences in their DNA. These natural differences mean that the antibiotics don’t kill a few bacteria (for one reason or another) and so they survive and continue to grow meaning that an infection can re-appear. This is why it is SO important to finish a course of antibiotics even if you feel better. The sheer concentration of antibiotics given to you means that hopefully, only 1%* of bacteria will survive, which is a manageable amount for the immune system. If you don’t finish the course of antibiotics you may leave these “super bacteria” behind and cause a real problem for yourself.
I have done a really quick video tutorial that will explain this idea more. You can find it here https://www.youtube.com/watch?v=qDIAVuHTYYk.
 This selection of super bacteria has given us the antibiotic crisis. Some of this 1%* of bacteria keep surviving no matter what and means that even the newest design of antibiotics won’t kill them. And if they do the antibiotic again selects a bacteria from these super bacteria that can survive etc, etc. This is what we call an evolutionary arms race, and means that there are more antibiotic resistant bacteria now than 10 years ago (you might have heard of a common one called MRSA).
Microbiology has however given us some more in depth knowledge about bacteria, and the discovery of Quorum Sensing is a real boost in this battle against bacteria. Quorum sensing is essentially how bacteria talk to each other2. Bacteria were always thought to be very anti-social, but this is not the case. Many bacteria wait until there are enough bacteria around them (a critical concentration of bacteria) and then start to talk to each other1,2. They do this by using signals (like texts) called autoinducers1,2. These are produced and released by the bacteria which cause a change in their DNA allowing certain genes to be turned on1,2. This can cause a number of different changes in the bacteria, for example, bacteria could form a biofilm1, or start producing disease causing factors1. Recent research suggests that if we can block these autoinducer signals we may be able to stop some infections caused by bacteria.

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  1. Miller. MB., Bassler BL., Quorum sensing in bacteria, 2001, Annu Rev Microbiol, 55: 165-99

  1. Williams. P., Winzer. K., Chan WC., Cámara M., Look who's talking: communication and quorum sensing in the bacterial world, 2007, Philos Trans R Soc Lond B Biol Sci, 362(1483):1119-34

*These figures are VERY rough guides and are not exact percentages of bacteria killed by antibiotics. Some antibiotics kill bacteria better than others and some bacteria are better at being resistant than others. What I'm saying is that if you want to know exact details you'd better google it.
I would also like to say that all the research into quorum sensing and the two references cited are not my own work and I give full credit to the authors of the papers (links by references).

Also another very important point ANTIBIOTICS DON'T WORK IF YOU HAVE A VIRUS!! So don’t complain to your GP about them not giving you anything for your virus. If they have you are putting yourself at risk from selecting super antibiotic resistant bacteria and you are wasting money and resources. I'm afraid you have got to just ride it out.