Unit 1: Microbiology Flashcards
Name the Features in the Bacterial Structure
Capsule, Cell Wall, Plasma Membrane, Cytoplasm, Ribosomes, Plasmid, Pili, Bacterial Flagellum and Nucleoid (Circular DNA)
What does Gram-Positive mean?
Types of Bacteria that have a thick Peptidoglycan Cell Wall, which helps protect the bacteria from antibiotics ando other substances that might damage them, but lacks an outer membrane
What are some examples of Bacteria that are Gram-Positive?
Staphylococcus aureus, Bacillus subtilis and enterococci
What does Gram-Negative mean?
Types of Bacteria that have a thin Peptidoglycan Cell Wall, which itself is surrounded by a lipopolysaccharide, but the cell envelope can produce endotoxins which produces symptoms of disease
What are some examples of Gram-negative Bacterias?
Escherichia coli, Pseudomonas aeruginosa, Protein mirabilis
What is the purpose of Gram-Staining?
To distinguish between the different cell envelopes, so classifying bacteria: Gram-Positive and Gram-Negative
Gram-stain results for Gram-positive
Since in Gram-positive, it has a low Lipid concentration, which is important for the retention of the complex iodine-crystal violet, when the primary stain (crystal violet) + Gram’s iodine is added, the cells remain blue. This is the same for the decolourising agent (ethanol 95%) and Counter stain (safranin)
Gram-stain results for Gram-negative
Since in Gram-negative, it has a high Lipid concentration found in the outer layers of the cell wall, it is dissolved facilitating the release of the iodine-crystal violet complex, leaving the cell colourless after the primary stain (crystal violet) and gram’s iodine is added. But when the decolourising agent (ethanol 95%) is added, the cell turns white. And when the counter stain (safranin) the cell turns red.
What does the Cell Wall Peptidoglycan consist of?
Two major amino sugars, N-acetyl-muramic acid and N-acetyl-glucosamine, and a chain of several amino acids is attached to each of the N-acetyl-muramic acid molecules
What are the membrane-associated proteins involved in the biosynthesis of Peptidoglycan?
Penicillin binding proteins (PBP)
What does the Cytoplasmic Membrane consist of?
40% lipid (phospholipid)
60% protein and small amounts of Carbohydrates
Sterols are absent
What is the purpose of the Cytoplasmic membrane?
Low molcular weight materials can penetrate to the inside of the cell.
Effective permeability barrier of the cell regulating the inflow and outflow of metabolites to and from the protoplast
Contain many proteins/enzymes which are essential to bacterium survival
Contain Vomit/Efflux Pump
Semi-Permeable
What does MAC grow?
Grows Gram-Negative Bacteria (e-coli)
Contains Lactose Fermenters
Present: Red/Pink colonies
Not Present: White colony
What does VJA grow?
Grows Gram-Negative Bacteria (Staph)
Contains Tellulite Coagulase which reduces it to Metallic Tellurite; pH altered Manitol Degredation
Present: Black colonies; Yellow Ajar
What does CET grow?
Grows Gram-Negative Bacteria (pseudo)
Present: Fluorescent Green Colonies
