Re: Bacterial mat below Earth's surface

I am not quite sure what "mat" you are referring to, but I can give you some information on microbial ecology in general.

When we dig into the soil, we actually go through layers of bacterial communities. On the surface are the organisms which compete the best in an environment with high amounts of oxygen, and the nutrients present in the soil. Further down in the soil, where oxygen is not plentiful, bacteria may use compounds containing nitrogen or sulfur or carbon dioxide (or many other compounds) to act as the oxygen does for the surface microorganisms. When oxygen is present, most of these bacteria from further down in the soil do not grow as fast as the bacteria which can use oxygen, so they do not get many of the nutrients, and they die. For some, oxygen actually kills them directly. In general, we do not have to worry about these organisms causing diseases. However, the most common disease-causing organisms found in soil are those which grow well with or without oxygen. These organisms are called facultative anaerobes.

You may have heard of one of the facultaive anaerobes called "E. coli," which grows in our intestines normally. If we get a new type of E. coli into our body, it does not perform the same functions in our digestive systems as the normal population of bacteria or the new population may grow too fast or produce a toxic compound. If any of these things happen, we get sick.

One place where a large mat of bacteria has been found is deep in the ocean. Bacteria grow in large masses around hydrothermal vents which provide heat to this environment. The ocean floor at these depths (usually 1000m or deeper) is usually near freezing. However, around these vents, it can be above the temperature of boiling water. The vents also supply large amounts of sulfur. The bacteria which can use sulfur in place of oxygen grow like crazy. Animals eat these bacteria, and a thriving community of clams, crabs, tube-worms, etc. is found in the middle of a barren ocean floor.

If you want to find out more information on these vent organisms, search for " hydrothermal vent" on the web.

I hope this has been helpful. Have fun!