Question 1 answer: Koch's postulates are a series of ground rules to determine whether a given organism can cause a given disease. , who developed a logical series of observations and experiments (Koch’s postulates) that proved the specific element of many infectious diseases, starting with anthrax. The series of steps worked out by Koch and others has become known as Koch’s postulates. He completed the famous postulates with anthrax. We instead use the Koch postulates because it is the best time-tested models for determining specific cause-and-effect in bacteriology.
mpkb.org/home/pathogenesis/kochs_postulates
Question 2 answer: Starch, glycogen, dextran and cellulose are all polymers ...view middle of the document...
All enzymes are unique. Only a specific enzyme with a specific substrate will create a reaction. Cellulose is the most abundant polymer on earth but only a few organisms have the enzyme to break down cellulose.
Talaro, K.P & Cowan, M. K., Microbiology; A System Approach (2007)
www.pslc.ws/macrog/starlose.htm
Question 4 answer: The bulk of the gram positive cell wall is a thick, homogenous sheath of peptidoglycan ranging from 20 to 80 nm in thickness and the gram-negative wall is a single thin (1-3nm) sheet of peptidoglycan. Gram-positive bacteria differ from gram-negative bacteria in the structure of their cell walls. The cell walls of gram-positive bacteria are made up of twenty times as much murein or peptidoglycan than gram-negative bacteria. These complex polymers of sugars and amino acids cross-link and layer the cell wall.
The thick outer matrix of peptidoglycan, teichoic acid, polysaccharides, and other proteins serve a number of purposes, including membrane transport regulation, cell expansion, and shape formation. Almost all bacteria can be classified as gram-positive or gram-negative. The classification relies on the positive or negative results from Gram’s staining method, which uses complex purple dye and iodine. Because gram-positive bacteria have more layers of peptidoglycan in their cell walls than gram-negative, they can retain the dye. Both gram-positive and gram-negative bacteria have a cell wall made up of peptidoglycan and a phospholipid bilayer with membrane-spanning proteins. However, gram-negative bacteria have a unique outer membrane, a thinner layer of peptidoglycan, and a periplasmic space between the cell wall and the membrane. In the outer membrane, gram-negative bacteria have lipopolysaccharides (LPS), porin channels, and murein lipoprotein all of which gram-positive bacteria lack.
As opposed to gram-positive cells, gram-negative cells are resistant to lysozyme (phagocytosis) and penicillin attack. The gram-negative outer membrane which contains LPS, an endotoxin, blocks antibiotics, dyes, and detergents protecting the sensitive inner membrane and cell wall.
LPS is significant in membrane transport of gram-negative bacteria. LPS, which includes O-antigen, a core polysaccharide and a Lipid A, coats the cell surface and works to exclude large hydrophobic compounds such as bile salts and antibiotics from invading the cell. O-antigen are long hydrophilic carbohydrate chains (up to 50 sugars long) that extend out from the outer membrane while Lipid A (and fatty acids) anchors the LPS to the outer membrane. A staining technique used to classify bacteria in which a bacterial specimen is first stained with crystal violet, then treated with an iodine solution, decolorized with alcohol, and counterstained with safranine. Gram-positive bacteria...
