What I see in Nature is a magnificent structure that we can comprehend only very imperfectly, and that must fill a thinking person with a feeling of humility.”
Albert Einstein
The residents of the Kingdom of the Archaea and the Kingdom of Bacteria are very similar. Nearly all of them are unicellular – made of just one cell as we said before. This single cell is also peculiar compared to our cells because it is far simpler. Most notably, archaea and bacteria all lack a nucleus, the part of our cells where the DNA is stored. Creatures without nuclei in their cells are known as prokaryotes. Until about 50 years ago, the Kingdoms of the Archaea and Bacteria were merged; they were only separated after scientists were able to examine their DNA and saw how different these two groups really are.
If we were to get out the atlas for the Kingdom of the Archaea, much of it would be labeled terra incognita – unknown lands (do you suppose they would draw a dragon?) because so far we have only explored parts of two phyla (or regions). The first phylum is the more diverse group, including archaea that live in extremely hot environments (up to 122ºC – well over the boiling point of water!), salty environments, as well as in the bodies of animals (those are the ones that produce methane). More recently, scientists have identified this type of archaea in fresh water and in soil. The second phylum is smaller, consisting mostly of archaea that live in the deep ocean, often around the exceedingly hot thermal vents. Archaea remain a poorly understood part of Creation, but scientists continue to study them to fill in map of this Kingdom.
The atlas of the Kingdom of Bacteria, on the other hand, is much more substantial: there are over 40,000 known species of bacteria in the world, and many more have not yet been discovered, with maybe 10,000 different species living just on people. Scientists have identified at least 30 phyla (regions in our atlas) of bacteria. Many of the phyla have been recognized only recently through examining the creatures’ DNA, so scientists often organize bacteria according to various characteristics, such as their shape or what types of environments they live in. One early type of classification was gram-positive and gram-negative, a grouping that is tested by gram staining the sample, a process discovered by a Danish doctor named Hans Christian Gram.
Like many scientific breakthroughs, gram staining was discovered through close observation and a bit of luck. Dr. Gram was studying lung cells from patients with pneumonia. He put a stain called crystal violet on the tissue and, to his surprise, the bacteria in the samples seemed to soak up the stain! Even when he tried to rinse the stain away, some of the bacteria still stayed the purple color. Some of the bacteria, though, went back to their original appearance, leaving two groups. Another scientist might have done this same thing before and never realized the significance, but Dr. Gram saw that this was a way of differentiating types of bacteria, what we now call gram-positive (they keep the purple color) and gram-negative (they don’t).
Another common way that scientists organize bacteria is by how they get their energy. Some bacteria are autotrophic (they produce their own food), while others are heterotrophic (they get their energy from other living things). Among those bacteria which are autotrophic, many make their food using the energy of the sun; scientists think that such bacteria living in the oceans produce half of the wold’s oxygen. Other autotrophic bacteria make their food using chemicals found in their environment, such as those that live around hydrothermal vents in the deep ocean.
Among those bacteria that are heterotrophic, some are symbiotic, they have a relationship with another creature that helps them both. For example, some bacteria live on the roots of bean plants; the bean plants feed the bacteria and the bacteria produces ammonia, an important chemical without which the plant cannot grow. Another group of heterotrophic bacteria is less helpful: pathogens that cause disease. These are probably the kind that are you are most familiar with – causing everything from acne to stomach bugs to Lyme disease. Fortunately, there are other bacteria who produce antibiotics – chemicals that kill bacteria. That’s right, the thing that we use to help us fight bacteria when we are sick comes from other bacteria (some also come from fungi)! Because archaea tend to favor more hostile conditions, they do not usually cause diseases. The last group of heterotrophic bacteria are decomposers, creatures that eat dead things. This might sound unpleasant, but just stop to think what would happen if all the leaves that fell in the forest each autumn just sat there and piled up, year after year, and nothing ever ate them to get rid of them. That forest would be buried in a hurry!
Bacteria do some pretty amazing things in our world, and we have only scratched the surface. Scientists are constantly finding new species, helping to learn more about creation and about the Creator, and maybe providing antibiotics that could help save lives in the future. Much of this Kingdom is still uncharted – adventure awaits!