BacteriaBacteria are the most common and oldest microorganisms on earth. Most bacteria are microscopic, measuring 1 micron in length. However, colonies of bacteria grown in a laboratory petri dish can be observed with the naked eye. There are many divisions and classifications of bacteria that help identify them. The first two types of bacteria are archaebacteria and eubacteria. The two groups have common ancestors dating back more than 3 billion years. Archaea bacteria live in environments where, due to the high temperature, no other life can develop. These environments include hot springs and areas of volcanic activity. They contain lipids but lack certain chemicals in their cell wall. Eubacteria are all other bacteria. Most of them are phototrophic, meaning they use the sun's energy as food through the process of photosynthesis. Another classification of bacteria is according to their need for oxygen to live. Those that require oxygen to live are considered aerobes. Bacteria that do not use oxygen to live are called anaerobes. The shape of specific bacteria allows the next step in the identification process. Spherical bacteria are called cocci; bacteria that are rod-shaped are called bacilli; the corkscrew-shaped bacteria are the spirilla; and filamentous is the term for bacteria with a threadlike appearance. Hans Christian Joachim Gram, a Danish microbiologist, developed a method to distinguish bacteria by their different reactions to a stain. The process of applying Gram stain is as follows: bacteria are stained with purple dye and treated with Gram's solution (1 part iodine, 2 parts potassium iodide and 300 parts water) . Ethyl alcohol is then applied to the support; the bacteria will retain the blue color of the original dye or obtain a red tint. Blue-colored bacteria are Gram positive; red bacteria are identified as Gram-negative. Bacteria contain DNA (deoxyribonucleic acid) like all cells. However, in bacteria, DNA is arranged in a circular fashion rather than in strands. Bacteria also contain ribosomes which, as in eukaryotic cells, ensure protein synthesis. For a bacteria to attach to a surface, it needs the help of pili, or hair-like growths. Bacteria, like sperm, have flagella that help them move. But sperm have only one flagellum, while bacteria contain flagella in several places all over their body...