Disease Seminar Handbook W12

15 type 2 diabetes you have been

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Unformatted text preview: mans and other animals. A bacterial cell consists of a tiny mass of cytoplasm surrounded by three distinct layers: the cytoplasmic membrane, the cell wall, and the capsule (Fig.1). 13 Within the cytoplasm is DNA, material containing genetic information. Unlike that of higher organisms, the DNA of bacteria is not enclosed in a membrane-bound structure, or nucleus. Some strains of bacteria have flagella that enable them to move with a swimming motion, or pili that help them adhere to certain surfaces (Fig.1). Some bacteria contain a special substance that allows them to emit light by a process called bioluminescence. Figure 1: General bacterium. Courtesy of http://www.singleton ­associates.org/bacteri2.htm Bacteria occur in a wide range of environments, but are most abundant in moist and moderate temperature climates. Most bacteria are heterotrophic; that is, they obtain food from other organisms; while others are autotrophic, or manufacture their own food. Heterotrophic bacteria usually feed on dead organic matter, although some species are parasitic. Most autotrophic bacteria use energy from sunlight to manufacture food by photosynthesis. Heterotrophic and autotrophic bacteria can be either aerobic or anaerobic. Aerobic bacteria live in environments in which free (molecular) oxygen is present; anaerobic bacteria live in environments in which free oxygen is absent. Bacteria generally reproduce by binary fission. Under favorable conditions, an adult organism splits apart to form two new organisms. Bacteria multiply rapidly, often doubling their population every 20 minutes. Some bacteria reproduce by budding, a process in which a small outgrowth from a single parent develops into a new, identical organism. A few bacteria can reproduce sexually (conjugation) under certain conditions. In this case two bacteria unite to form a zygote, which then splits into new cells. Some bacteria form colonies that may become large enough to be seen with the unaided eye. Based on cell wall composition, bacteria can be separated into two groups; Gram-positive and Gram-negative. These bacteria react to the stain called as the Gram stain. The cell wall of the Grampositive bacteria is made up of many layers of peptidoglycan and teichoic acids. The gram-negative bacteria have a slightly thinner cell wall made up of a few layers of peptidoglycan. They are 14 surrounded by another layer of lipid membrane containing lipo-polysaccharides and lipoproteins. Most bacteria have the Gram-negative cell wall. Figure 2: The cell wall composition of Gram-positive and Gram-negative bacteria. Courtesy of http://silverfalls.k12.or.us/staff/read_shari/mysite/chapter_24_ab.htm Figure 3: The cell wall composition of Gram-positive and Gram-negative bacteria. Courtesy of ht http://www.websters-online-dictionary.org Classification of Bacteria Bacteria are generally classified by two methods. The simplest and oldest method is by shape. The three principal categories are ba...
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This note was uploaded on 01/27/2014 for the course BIOL 1080 taught by Professor Dyck during the Winter '11 term at University of Guelph.

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