Understand The Difference Between Gram-Positive And Gram Negative Bacteria

To fully understand this lab we first need to know what gram-negative and gram-positive bacteria are and what it’s composed of. Gram-positive bacteria take up the class of bacteria that stain crystal violet in the method of bacterial differentiation. Where gram-negative bacteria are a class of bacteria that does not retain crystal violet. Instead they are counter-stained pink by Safranin, and because of this, identifying positive is possible. One of the many differences between gram-negative and gram-positive bacteria is their peptidoglycan. Which are attached polypeptides to form networks that surround and protect the entire cell. The peptidoglycan is pretty much what acts as their backbone. Knowing where to locate it and the amount of it
When gram-negative dies, they release lipid A and functions as endotoxin. Core polysaccharide is attached to lipid A and provides stability. Lastly, O polysaccharide is what extends outward from the core polysaccharide and functions as an antigen. O polysaccharide is useful for differentiating species of gram-negative bacteria. Lipoproteins are what connect the outer membrane to the peptidoglycan. The plasma membrane of these bacteria’s contains phospholipid molecules that are arranged parallel to each other called a lipid bilayer. The surface of the lipid bilayer are polar heads composed of a phosphate group and glycerol that is hydrophilic (water loving) and are soluble in water. Nonpolar tails are in the interior of the bilayer. These nonpolar tails are composed of fatty acids that are hydrophobic (water fearing) and not soluble in water. To contain, protect, and provide structure are the functions of the plasma membrane. It is selectively permeable and helps control what moves into and out of the cell. These are just the basic steps to know in order to understand this lab. It’s mostly like a puzzle that’s just waiting to be put
One way to do this is through selective and differential media where they are used to isolate or identify particular organisms. Selective media allow certain types of organisms to grow and inhibit the growth of other organisms. Selective inhibition for some kind of microorganisms can be achieved by adding dyes, antibiotics, salts, or specific inhibitors that affect the metabolism or enzyme system of that organism. Differential media are used to differentiate closely related organisms or group of organisms. There are certain dyes or chemicals inside the media that bacteria will react to. These reactions can either be characteristic changes or growth patterns which are useful for identification or differentiation of microorganisms. Four kinds of cultured media are used in this lab experiment. The first one I will be talking about is the Eosin Methylene Blue agar or EMB for short. EMB is a selective and differential medium that inhibits the growth of gram-positive, but detects and isolate gram-negative enteric bacteria. Mythelene blue inhibits gram-positive. The selective part is used for inhibiting gram-positive and has methylene blue. The differential part is what ferments lactose. MacConkey agar is a selective and differential media used to isolate gram-negative bacteria and differentiate between lactose fermenting and