Prokaryotic Factoids

Prokaryotes! The prolific group of simple, single-celled organisms that ruled Earth for 1.5 billions years until Eukaryotes and their nucleus's came along. And even though multicellular Eukaryotes (plants, animals, fungi, protists) appear to dominate the planet, prokaryotes are still the most abundant form of life. One drop of seawater contains hundreds of thousands of prokaryotic organisms, a spoonful of soil contains billions, the average human body is home to trillions. I'm sure you've read before, that about 250,000 average-sized prokaryotes can fit within the period at the end of this sentence. Bacteria and Archaea (the two main groups of prokaryotes) are incredibly tiny, but not all of them are. Theomargarita namibiensis, the largest known bacterium, is 700 micrometers in diameter - visible to the naked eye!

Different types of prokaryotes can inhabit nearly any place on Earth, often places where nothing else can live. Some bacteria can live in near-boiling hot springs, while even tougher archaea can happily inhabit water over 230°F (in fact, it will stop growing if temperatures drop below 194°F). Others make their home in Antarctic sea ice. Some species of prokaryotes can be found perpetually crushed by high pressure 1.7 miles below the Earth's surface. Waters as acidic as vinegar or alkaline as household ammonia don't deter some species. Even the Dead Sea, where salt concentrations are seven times that of the ocean, is a home for colonies of tough bacteria and archaea. Bacteria has even been found dormant in the intestines of a mammoth buried in a peat bog for 11,000 years!

If these facts give you dismay that we shall become overrun by microscopic "inferior" beings that cannot be destroyed - don't worry. No single prokaryotic species can survive all these pressures. Most prokaryotes live harmless, specialized lives, in moderate habitats. Popular places include your very own intestines, mouth, skin, and respiratory tract. But before you embark on a prokaryotic killing spree to rid yourself of these invaders, remember that bacteria and archaea fill important and essential roles, not only in our bodies, but on the entire planet. In fact, we are dependent on prokaryotes for our existence. They help us digest our food and absorb vital nutrients. They break down and recycle wastes and dead organisms. They capture nitrogen from the air for plants, who would perish without it. Prokaryotes can even help us clean up our own messes, such as oil spills. When the Exxon Valdez polluted Alaska's Prince William Sound with 11 million gallons of crude oil, the beaches were sprayed with a fertilizer that encouraged the growth of an oil-eating bacteria.


Prokaryotes may be the simplest life-forms on Earth, but they are essential for the existence of all other life. These under-appreciated organisms should be celebrated for their diversity, their versatility, and their importance in the world!

Source:
Biology Life On Earth, with Physiology (Eighth Edition)
by Teresa Audesirk, Gerald Audesirk, Bruce E. Byers
(Pearson Prentice Hall, 2008)