Tag Archives: bacteria

The next generation of Antibiotics?

Posted on November 5, 2012 by | 1 comment

Imagine yourself in a world where there is absolutely no treatment for any type of disease caused by bacteria, because of the rise of “superbugs” or antibiotic-resistant bacteria.  This could be the future we could be facing if we continue to over-use conventional antibiotics.

There is no doubt that one of the greatest achievements of the past century was the discovery of antibiotics. Antibiotics treat bacterial infections by killing bacteria or by inhibiting their growth. They do work very well; unfortunately, one major flaw in the current antibiotics is that they cause surviving bacteria to develop resistance.  In other words, treatable infections becoming untreatable, due to over use of antibiotic treatments. Therefore, we should pursue a different approach when it comes to dealing with bacteria.

One such approach is to prevent bacteria from “talking” with each other in other words, preventing bacteria from using quorum sensing.  Quorum sensing is how bacteria communicate with one another through chemical signals.  Quorum sensing is particularly important for bacteria that cause disease (pathogenic bacteria). These bacteria use quorum sensing to coordinate their “assault” on their host, and helps them escape from the response from their host’s immune system.

Bioluminescence, a process, that is achieved only with quorum sensing. From http://jb.asm.org

Here is a video of Dr. Bonnie Bassler, from Princeton University, explaining how bacteria “talk” to each other, and what the potential applications are towards controlling bacteria:

YouTube Preview Image

As explained by Dr. Bassler, the biggest application from manipulating quorum sensing is antibiotics. Since disease-causing bacteria use quorum sensing to “attack” their hosts, we could stop these bacteria from using quorum sensing, and therefore they will not cause their disease.

Is there any evidence of this approach actually working? According to a article, by Thomas Rasmussem, and Michael Givskov, they have identified some chemicals that are quorum sensing inhibitors.  These chemicals were found to reduce the ability of bacteria to survive and cause disease.  They also examined other ways on how to stop quorum sensing, such as preventing formation of quorum sensing molecules, and degrading quorum sensing molecules. Clearly, the results of the study show the potential of anti-quorum sensing chemicals. Hopefully, enough potential to remove the threat of bacteria once and for all.

– Dominic

1 Comment

Posted in Biological Sciences, Issues in Science

Tagged , , , ,

Microbes with Arsenic DNA Backbones: Fact or Science Fiction?

Posted on October 20, 2012 by | 2 comments

In December of 2010, the National Aeronautics and Space Administration (NASA) took the scientific world by storm with a press release stating that a news conference would be held to “discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life”. At the press conference, NASA scientist Felisa Wolfe-Simon claimed to have found a microbe that was able to incorporate arsenic as a substitute for phosphate in the DNA backbone. This conclusion was reached since the microbe managed to grow even in conditions with high arsenic concentrations and low phosphate concentrations. This microbe, strain GFAJ-1 of the Halomonadaceae, was isolated from Mono Lake, California, a lake known for its toxicity in the form of extremely high concentrations of arsenic.

Picture of GFAJ-1: (Creative Commons License: image by Jodi Switzer Blum)

Wolfe-Simon’s reasoning was that because arsenic is directly below phosphate in the periodic table, it has a similar chemical reactivity which allows it to be substituted for phosphate in the DNA backbone. According to NASA, the implication of this research is that the long-held assumption that all life on earth, from the tiniest microbe to large mammals, depends on six essential elements, one being phosphorus, may be wrong.

NASA sensationalized the implications of Wolfe-Simon’s research; it was claimed that the exploration for alien life that previously only included searching for the six essential elements, would have to be modified to include arsenic. A whole new branch of previously unexplored life forms could exist.

 However, the scientific community was not as receptive as the public to Wolfe-Simon’s work. Shortly after the online publication of Wolfe-Simon’s paper, an avalanche of criticism descended on the paper in the form of dozens of technical responses and online responses to the paper by skeptical scientists. The methodology of Wolfe-Simon’s experiment, the data analysis and the interpretation of results were all thoroughly criticized.

Here’s a video of the NASA Press Conference announcing Wolfe-Simon’s work. From 0-2:55, Wolfe-Simon provides the motivation for her work and from 2:56-9:39, Dr. Steven Benner, Founder and Distinguished Fellow of the Foundation of Applied Molecular Evolution, discusses why he is skeptical of Wolfe-Simon’s conclusions.   (attribution: rrhea22)

YouTube Preview Image

Rosie Redfield, a microbiology professor at the University of British Columbia, has been one of the leading voices in the criticism of Wolfe-Simon’s work; along with a scathing blog post about Wolfe-Simon’s research two days after it was published,  she later published an article refuting Wolfe-Simon’s conclusions about the ability of GFAJ-1 to incorporate arsenic in its DNA backbone entirely. Redfield showed that GFAJ-1 was unable to substitute arsenic for phosphate in the DNA backbone through growing the microbe in the same conditions described by Wolfe-Simon, then analyzing the DNA strands for arsenic incorporation.

For all of us out there in the world fervently hoping for a new avenue of previously unexplored alien life forms, it looks like GFAJ-1 does not provide proof that there is an organism able to incorporate arsenic in place of phosphorus. This doesn’t mean there aren’t any organisms able to do this out there in the world, it just means we have to keep on exploring and researching!

References:

http://science.nasa.gov/science-news/science-at-nasa/2010/02dec_monolake/

https://www.youtube.com/watch?v=W_Nz_6Pbydo&feature=related

https://www.youtube.com/watch?v=5GKmKyfXuFw

http://www.slate.com/articles/health_and_science/science/2010/12/this_paper_should_not_have_been_published.html

http://www.washingtonpost.com/wp-dyn/content/article/2010/12/02/AR2010120204183.html

http://www.sciencemag.org/content/332/6034/1163.abstract

http://www.sciencemag.org/content/337/6093/470.short

 

2 Comments

Posted in Biological Sciences, Issues in Science, Science in the News

Tagged , , , , , , , , ,

When in doubt, throw it out!

Posted on October 1, 2012 by | 5 comments

You’re up late studying for midterms, desperately trying to avoid blinking for fear of falling asleep. As a quick pick-me-up you reach for a piece of Halloween candy. You open the wrapper and in your sleep-deprived state, your candy falls to the floor. According to an old wives tale, you have approximately 3-5 seconds to grab your tasty treat before it becomes covered in bacteria and whatever else might want a bite. Your candy is sitting on the floor, helpless. Regardless of whether it’s two seconds after you dropped it or six, you pick it up. Apart from the stray fluff from your fuzzy socks, it looks relatively unharmed. Now, the big question: do you eat it?

According to researchers, the answer is a resounding NO. Bacteria and other microorganisms immediately contaminate food that falls to the floor. There are some factors to take into account but in general, it is safer to ditch the dropped food. This is why some researchers think we should be using a ‘when in doubt, throw it out’ philosophy as opposed to the mythical ‘five second rule’.

Two factors that determine how many bacteria end up on your food are the moisture content of the food and the cleanliness of the surface upon which it falls. Moist food, such as cheese or meat, is quite easy for bacteria to stick to and ends up with higher bacteria contamination when dropped. Bacteria have a more difficult time with dry food, such as crackers or cookies, which don’t become contaminated as easily. As for the surface in question, obviously a cleaner surface will have less bacteria and a lesser chance of contaminating dropped food. Watch here as Dr. Philip Button outlines his take on these two factors:

YouTube Preview Image

But what about the length of time food is left on the floor? It has been shown that the difference in amount of bacteria on food that was left for two seconds or six seconds is not significant. If bacteria are there, they are going to be on that food faster than you can react.

And what about wiping it off? Or rinsing it with water? Once food has been dropped or has touched something it shouldn’t, there is really no way to get it back to its original state. Wiping or rinsing may get rid of some bacteria, but it cannot get rid of them all.

So if you drop a piece of dry food on a clean surface, what’s the big deal? As clean as the surface may be, you don’t really know which bacteria are present. The bacteria that end up on the food may require only a small number of organisms to be present in order to cause disease, which could be costly for someone with a weak immune system.

The next time you drop a piece of food on the floor, think about the circumstances under which it is falling and who will be eating it. Remember: when in doubt, throw it out!

-Karly Stillwell

5 Comments

Posted in Biological Sciences

Tagged , ,