Re: What is there to know about anaerobic bacteria?

Hi Silas,

Anaerobes (literally meaning "without air") are organisms that do not use oxygen to live. If the anaerobe dies in the presence of oxygen, it is a strict (obligate) anaerobe. If the anaerobe can tolerate oxygen even though it does not use oxygen, it is an aerotolerant anaerobe. You might have learned about five different kingdoms of organisms in your biology classes (animal, plant, fungi, protist, bacteria), but the most current classification scheme only includes three groups (archaea, bacteria, eukarya). The archaea, eukarya, and the bacteria all contain anaerobic organisms.

Aerobic organisms use oxygen in their metabolism. Oxygen is a "terminal electron acceptor" at the end of a metabolic pathway that provides energy for organisms. What this means is that at the end of complicated biochemical pathway that involves juggling electrons around and making energy, an oxygen molecule accepts an electron and hydrogen atoms to become a water molecule. For more detail about this, I'd suggest going to the following website:
http://www.sp.uconn.edu/~terry/images/anim/ETS.html which has an animation of the electron transport chain.

Anaerobic organisms use different molecules as electron acceptors, such as sulfide or carbon dioxide. In fact, these organisms are incredibly diverse when it comes to the nutrients that they can use to survive. The website http://www-micro.msb.le.ac.uk/109/Environmental.html
should give you an idea of different types of metabolism used by organisms in particular environments.

On Earth, you'll find anaerobic organisms all over the place, including in your intestinal tract, in oil pockets, and in sediments on the ocean floor. Basically, anywhere there is water you'll find organisms. Since Earth and Mars are thought to have been similar early on (about 4 billion years ago), there is an idea that life might have evolved on both planets, or that life started on Mars and then came to Earth via meteorites.

Organisms that live in extreme environments (called extremophiles) here on Earth could be similar to Martian organisms that exist, or existed in the past, or could exist on Mars. The search for life on Mars focuses on the Martian sub-surface, in places that are analogous to hydrothermal systems here on Earth. Hydrothermal systems are regions of hot water (around 100 degrees Celsius!) in which organisms have been found to grow. If you have ever visited Yellowstone National Park, you have seen some of these hot springs. There are also organisms that live in extremely cold environments on Earth, such as in Antarctic soil. Studying these creatures is relevant to Mars research since the near-surface environment of Mars is very cold. Other places where extremophiles have been found on Earth are in extremely acidic environments and high pressure regions under the bottom of the ocean. If microbes can thrive in the stomach acid of your gut, you can imagine that they're going to be able to thrive just about anywhere!

If you need more information about this, feel free to write back and I'll be happy to answer your questions. If you want to know more about life on other planets, NASA has a webpage dedicated to this topic:
http://astrobiology.arc.nasa.gov/index.cfm that you can search.

Sarah Earley
CU Boulder