Most people are familiar with bacteria because they are responsible for many illnesses such as kidney infections and some types of pneumonia. Antibiotics are prescribed when bacteria are believed to be the cause of disease.
"Good" bacteria are those that live symbiotically with other organisms. In humans, they help break down nutrients in the gut and create molecules that can be used by our bodies. Consuming yogurt and other probiotic foods replenishes the helpful bacteria in our bodies and helps to fight off yeast infections. Some bacteria live on the roots of plants and convert nitrogen into ammonia that can be used by the plants, a process called nitrogen fixation.
Prokaryotic Cells
These prokaryotic organisms do not have a cell nucleus. Their DNA is located in the cell's cytoplasm with all of the other intracellular structures and forms a tangled body known as a nucleoid. According to the article, "Bacteria: More on Morphology," (accessed April 26, 2010) by Ben Waggoner of the Department of Biology at the University of Central Arkansas, and Brian R. Speer of the University of California in Berkeley, "Plasmids, or small loops of DNA, can be transmitted from one cell to another, either in the course of [sexual reproduction] or by viruses. This ability to trade genes with all comers makes bacteria amazingly adaptable; beneficial genes, like those for antibiotic resistance, may be spread very rapidly through bacterial populations."
Gram Stain of Peptidoglycan within the Bacterial Cell Wall
Archaea and bacteria used to be classified under one domain: the Prokaryotes. The organisms often had the same appearance and functions, but important differences were discovered that led to the division of this domain into the two domains of Archaea and Bacteria. Peptidoglycan is one of the most important differences between bacteria and archaea. The bacterial cell wall contains layers of peptidoglycan whereas archaea have no peptidoglycan. It is important to note that mycoplasmas are a type of bacteria that does not have a cell wall, and therefore no peptidoglycan.
Gram staining is used to classify bacteria into one of two types: Gram-positive and Gram-negative. The identification is based on the amount of peptidoglycan present in the cell wall. Gram-positive bacteria's thicker cell wall contains many layers of peptidoglycan and will stain purple, whereas Gram-negative bacteria have fewer layers and will stain pink.
Similarities of Bacteria to Eukaryotic Organisms and Archaea
Bacteria share common genes with both archaeans and eukaryotes. Human cells, for example, contain mitochondria that produce energy for cell processes. Mitochondria have their own genetic material which is different from that within the cell nucleus, and comes from bacterial genetic material.
The domain Bacteria has two important differences that set it apart from the Archaea and Eukarya. Unlike Eukarya, Bacteria are prokaryotes having no cell nucleus. Also, organisms in the domain Bacteria have peptidoglycan in their cell walls, a structural characteristic that is not shared with the other two domains.
Diane Ursu - Diane Ursu joined Suite101 as a contributing writer in August 2009 and became a Feature Writer in January 2010. She is a freelance writer ...
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