Bacteria are everywhere!

You and the world that surrounds you are covered with bacteria.

Bacteria are found almost anywhere on Earth — from the top of Mount Everest to the bottom of the ocean. They are not seen because they are very small, and they can be identified only with the help of a microscope. In fact, bacteria are so tiny that 300 could fit end-to-end across the period that ends this sentence.

Bacteria Basics

Bacterium cellular structure

ARCHAEBACTERIA are found in harsh environments such as salt lakes, hot springs, and hydrothermal vents at the bottom of the ocean. Because they survive, and even thrive, in these extreme conditions, biologists theorize that they were the first organisms to colonize Earth during its early history.

Fossil records support this theory. Rocks containing bacteria have been dated at 3.5 billion years old! Archaebacteria are very similar to Eubacteria, but have genetic traits that resemble eukaryotes. Some scientists now suggest that multicelled organisms evolved from these primitive bacteria.

Most bacteria are in the EUBACTERIA kingdom. They are the kinds found everywhere and are the ones people are most familiar with. Eubacteria have been on Earth almost as long as the Archaebacteria and were instrumental in creating a suitable environment for other forms of life. There are many methods to classify bacteria, but the simplest way is according to their shape. The following shapes are the most common:

Shapes of Bacteria Shape Characteristics Examples Sphere-shaped bacteria Sphere-shaped bacteria (cocci) sometimes grow in chains or in clumps like a bunch of grapes. Streptococcus (strep throat) Staphylococci (responsible for "staph" infections and gangrene) Rod-shaped bacteria Rod-shaped bacteria (bacilli) can also form in chains. Some types of these bacteria also have whiplike structures called flagella to help them move around. Escherichia coli or E.coli (found in the intestines of mammals) Salmonella typhi (causes typhoid fever and food poisoning) Spiral-shaped bacteria Spiral-shaped bacteria (spirilla) can use their shape to propel themselves by twisting like a corkscrew. Treponema pallidumcholera (syphilis) Borrelia burgdorferi (Lyme disease)

Another technique to identify bacteria is to stain them with a dye. This method is called a GRAM STAIN. Some cell walls change colors when stained and other cell walls do not. The bacteria that have the stained cell walls are called Gram positive. The bacteria with cell walls that do not stain are called Gram negative. Doctors regularly use gram staining to select the proper antibiotic to treat bacterial infections.

Living the Simple Life

Cyanobacteria are the architects of Earth's atmosphere.

Several other types of bacteria are autotrophs, organisms that can produce their own food. Like plants, some bacteria (such as cyanobacteria) use sunlight in the photosynthetic process to obtain food. Other bacteria are CHEMOSYNTHETIC, using nitrogen- and sulfur-containing compounds to obtain the necessary nutrition and energy to survive.

An animation of binary fission

Bacteria reproduce asexually by splitting themselves in half in a process called BINARY FISSION. During this process, one cell splits into two identical cells, which are sometimes called CLONES. Over time, these dividing bacterium cells often group together in colonies. Bacteria multiply quickly. In fact, one cell can replicate into over a million cells in just 12 hours. In contrast, a human cell takes 24 hours to split.

Bacteria: The Ultimate Survivor

Geological Survey of Western Australia

Acaciella australica is an 800-million-year-old stromatolite formed by cyanobacteria.

Biologists have determined two reasons for bacteria's successful adaptation. The first reason is related to the fact that they reproduce very quickly. Because bacteria make copies of DNA so frequently, copying mistakes are bound to be made. Those mistakes are called MUTATIONS. Natural selection predicts that the bacteria best-suited to the environment will survive. With all those mutations, one of them is bound to survive!

Another way bacteria adapt is called GENETIC RECOMBINATION. Sometimes, one bacterium will absorb DNA inside the cell from another bacterium and add it to their own DNA. In this way, the bacterium can gain new, beneficial genes to its DNA. Mutations and genetic recombination are what make bacteria so flexible and adaptable.

Bacteria: Friend or Foe?

Bacteria 500 Instructions: Answer the questions. For each correct answer you give, your car moves ahead one space. Each wrong answer advances your opponent's car one space. Do you know enough to win the race? Happy racing! Click Here!