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Dangerous Experiments

Dangerous Experiments is the LabSpaces spot for guest bloggers. The purpose of the blog is to give new and old bloggers a space to experiment with blogging. If you'd like to contribute to this experiment, send us an e-mail or contact us on twitter at either @LSBlogs or @LabSpaces.

My posts are presented as opinion and commentary and do not represent the views of LabSpaces Productions, LLC, my employer, or my educational institution.

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Monday, June 27, 2011

This week's guest blogger is Ryan Renslow. He is currently a Ph.D. candidate at Washington State University in the Gene and Linda Voiland School of Chemical Engineering and Bioengineering (say that five times fast!). You can follow him on twitter (@BiofilmResearch) to learn all about biofilms and his research!

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Dental plaque Credit: Bob Blaylock/CC3.0

Until recently, most of the general public has never heard of or used the word "biofilm". Thanks to Listerine, and their "biofilm fighting" mouthwash, this is no longer true. Listerine commercials, featuring their new antiseptic product, have indoctrinated our culture to believe that "biofilm" is merely 2011-speak for plaque. However, biofilm is not simply a new advertising buzzword, but rather it has actually been used in the scientific research community since the late 70's and refers to much more than simple oral plaque. To be clear, plaque is known as a biofilm in dental and oral science literature, so Listerine is correct, but biofilms are much more than what the commercials depict.

Bacteria live in two primary modes of life: the planktonic form and the biofilm form. The planktonic form refers to free floating cells, and the word itself is derived from the Greek adjective planktos, which means wanderer or drifter. Generally, cells in the planktonic form are considered their own independent entity, with little regard to their floating neighbors. Biofilms, on the other hand, are groups of cells that live together in a community, and form "biological films" on surfaces or interfaces. The cells in biofilms attached to each other and to the surface, and for the most part, stay put. Some people have described biofilms as "cities of bacteria". Despite cells being discovered in the biofilm form more than 100 years ago, the general bulk of science literature has been devoted to cells in the planktonic form. However, in the past two decades, research of bacteria in the biofilm mode has increased exponentially. This is primarily due to the recent recognition that bacteria predominantly choose to live in the biofilm mode. The National Institutes of Health (NIH) report that around 80% of all human bacterial infections are biofilm related, and even in the environment, 80% of bacteria happily dwell in biofilm formations.

All this talk about biofilm plaque and biofilm infections may lead people to believe that all biofilms are bad, and that research scientists (and Listerine) are striving to destroy them. That is true in some cases, however, there are "good guys" too. Good biofilms are being used in wastewater treatment facilities to clean up human waste, in research labs to create fuels and products like hydrogen and ethanol, and in microbial fuel cells to create electricity. For the past several years, my research has focused on understanding the biofilms that are capable of creating electricity.

The idea of creating power or electricity from a living organism like bacteria is nothing new. Luigi Galvani, the famous Italian physician, spearheaded research in "bioelectricity" back in the 18th century. Most people are familiar with his work because it inspired parts of Mary Shelley's 19th century novel, Frankenstein. While there has been significant scientific progress since Galvani's time, the principal that electricity can be generated from living organisms is still true. Certain types of bacterial biofilms, dubbed electrochemically-active biofilms, have the ability to transfer some of the electrons that they generate through normal metabolism to an external solid electrode. This is the principal utilized in microbial fuel cells. These devices often go by other names, including mud batteries, bioelectrochemical systems, or sediment fuel cells. While still in the development phase, these alternative energy devices have successfully been deployed by the US Navy to power remote ocean sensors to measure temperature, pressure, underwater sound, and chemicals in the water.


Soil microbial fuel cell Credit: MFCGuy2010/CC3.0

The ability for bacteria to transfer electrons to a solid electrode in their external environment gives them a huge survival advantage. To understand this, it is important to first remember the basics of how organisms gain energy. Organisms intake food to provide nutrients, which are broken down to release electrons. These electrons are used to drive several reactions, the primary one being the production of adenosine triphosphate (ATP). ATP is used as the main source of energy to power cellular reactions, including DNA and RNA synthesis, molecular transport, and the synthesis of proteins and other macromolecules. Without ATP, we would not be able to move, breath, think, or live. At the end of these reactions though, the electrons that were originally harvested to drive ATP production need to be disposed of once their useful energy has been depleted. This is why we have to breathe: we dump the used electrons to oxygen, which combines with carbon to form carbon dioxide. Bacteria also undergo the process of respiration. However, oxygen is not always available in their environments. Without oxygen or another electron acceptor available, "normal" bacteria would essentially suffocate. This is why having the ability to transfer electrons to a solid electrode provides a survival advantage for electrochemically-active bacteria. They have the ability to "breathe" using solid electrical conductors in locations where oxygen is not available. In the environment, this solid electron acceptor usually takes the form of iron- or other metal-laden minerals. In the lab, the minerals are replaced with inert electrodes, which are connected to an electrical circuit, and Voila!, we're able to take the organisms waste electrons and capture them as electricity.

In order to make microbial fuel cells commercially viable, there is still a lot of research that remains. One of the Holy Grails in biofilm research is trying to understand exactly how the electrons are transferred from the cells in the biofilm matrix to the electrode. Once this is fully understood, the process can be engineered and optimized in a way to increase power outputs. This research is also leading to novel methods to help prevent or kill harmful biofilms. Which leads us back to Listerine… while I appreciate the fact that society is becoming more familiar with the term "biofilm" due to their "biofilm busting" commercials, I wish that everyone could understand how much more there is to this exciting research area than just plaque!

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Very nicely written. Thank you!

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