Microbiology
Americans are fascinated by world records. The Guiness Book of World Records is a very popular text because we are interested in the biggest and the best of everything.
In the late '80s a Dr. Fishelson found a very unusual bacterium called Epulopiscium fishelsoni. This bacterium lives in the gut of a Red Sea surgeonfish. This bacterium can grow up to 600 micrometers long and 80 micrometers wide. The average Epulopiscium fishelsoni is 250 micrometers long and 40 micrometers wide. Six hundred micrometers is a little over a half a millimeter. A millimeter is about as long as the period in the box below.
1millimeter=.
The human eye can see things as small as 200 micrometers, making this bacteria the first one to actually be visible to the naked eye. To give you a better idea of how big this bacterium really is, "normal-sized" bacteria are only about 0.2 micrometers to about 1.5 micrometers in length or diameter.
In the microbial world a record has finally been broken for the biggest bacteria in the world. The record holder for the biggest bacteria recorded on the earth is now (drum roll please): Thiomargarita namibiensis. This behemoth of bacteria is round rather than rectangle like Epulopiscium fishelsoni. It averages about 180 micrometers in diameter. The largest cells have been measured at 750 micrometers. On a cell volume basis the largest Epulopiscium fishelsoni is .003 millimeters cubed. However, Thiomargarita namibiensis' largest cells have an enormous volume of 0.22 millimeters cubed.
Not only is Thiomargarita namibiensis a giant but it is also very unusual. It utilizes sulfates and nitrates to get its energy. This bacteria found off the coast of Namibia is in the sediment at the bottom of the ocean. Basically, Thiomargarita namibiensis gets necessary electrons from sulfates. It then uses nitrates to grab onto the electron instead of oxygen. Those electrons are eventually used to generate energy for the cell. It gets its enormous size because it stores huge amounts of nitrates to hold onto these electrons. It needs to store the nitrates because nitrate levels are very low in these waters most of the time. It isn't until a major storm stirs up the mud at the bottom of the ocean that Thiomargarita namibiensis can get the nitrates it needs.
When nitrates are around, these bacteria literally stuff themselves with nitrate. In essence they are a huge ball of nitrates with a very thin layer of cytoplasm (cytoplasm contains all the necessary stuff for bacteria to live, grow, and reproduce) around this nitrate.
This bacteria may prove useful in other areas of the world's oceans.
In waters contaminated with nitrates from fertilizers and sewage these organisms may be useful in taking up these nitrates. If too much nitrate is in the water, algae in the water will grow out of control and kill or chase away other inhabitants in the area. Thiomargarita namibiensis could be placed in these nitrate rich waters to remove them and prevent the algae from growing out of control. There needs to be a lot more work done on this unique bacterium. Researchers have yet to get it to grow in a test tube. However, in time this giant among bacteria may be tamed and utilized to help in other areas of the world.
For more information go to the Science(April 16, 1999, vol. 284, No.5413, pages 415 and 493-495) article. You can't get all the information from the online version unless you are a subscriber. On the other hand, the cover of that issue has a picture of this mighty bacteria.
Take Care and Think Microbiologically!