University:
University of Alberta
Course:
MMI 133 | Medical Microbiology for Health Care Professionals
Academic year:

2024
Views:

362

Pages:

4
Author:

Ali O

x Lecture 1 Theory of spontaneous generation: a theory proposed by Aristotle which stated that living organisms could arise from non-living matter ↳ Louis Pasteur disproved this theory Germ Theory of disease: Louis Pasteur states in his theory that many diseases are caused by microorganisms such as bacteria, viruses, protozoa, or fungi Size of Microorganisms Prions Smallest Virus Prion: a type of protein that can trigger normal proteins in the brain to fold abnormally. They do not contain any nucleic acid or genetic material Bacteria Virus: a non-living organism that can only grow and Fungi reproduce in the cells of a host Parasites Bacteria: single-celled organisms that produce their own Mammals energy and can reproduce on their own Fungi: multicellular eukaryotic organisms Micro- and macro- scopic Largest Are Bacteria Bad? · Bacteria can break down and create things that your body needs · Bacteria also help fight off disease · However, some strains of bacteria have virulence factors which cause them to damage tissues Naming Microorganisms: Organisms are classified into families on the basis of the relatedness of their ribosomal RNA or rRNA examples: Staphylococcus aureus (S. aureus) Staphylococcus epidermidus (S. epidermidus) Salmonella typhi (S. typhi) When shortened its hard to tell the genus so you have to know both (subspecies) Bacterial Shapes (Morphology) Coccus (spherical) Bacillius (rod-shaped) Diplococci Spirillum (corkscrew-shaped) Coccobacilli Vibrio Diplobacilli Streptococci Spirillum Streptobacilli Staphylococci Spirochaete How to tell bacteria apart if they are the same shape? 1. Simple Stains ↳ Only show that bacteria are present but not specific kinds 2. Differential Stains ↳ Gram Stain: separates bacteria into gram + and gram i n ↳ Acid Fast Stain: used for mycobacterium ~ (Pink) staining is based on cell wall structure and amount of peptidoglycan in cell wall (Purple) How to Gram Stain: ① Fix the specimen onto the slide by using heat or methanol ② Add Crystal Violet to create the primary stain ③ Add Iodine to the slide (acts as a mordant) wash off excess ④ Decolourize with acetone or alcohol. This is the differentiation step ⑤ Add Safranin to counterstain gram negative bacteria Explanation: Inside the Peptidoglycan layer of the bacterial cell, crystal violet and iodine bind together to make the larger molecule. This large complex molecule will be trapped inside of gram-positive organisms because they have a thick peptidoglycan layer in their cell walls. A mesh forms, Gram-negative organisms will have all stain removed after decolorization. In order for us to see them in a microscope counterstain is applied colouring them pink. Gram-positive organism remain dark purple throughout the procedure Gram positive is not decolourized by alcohol Thin layer of peptidoglycan is gram positive