Microorganisms- minute living things that individually are usually too small to be seen with the unaided eye. AKA microbes.
Microorganisms include bacteria, fungi (yeasts and molds), protozoa, and microscopic algae.
Prokaryotic Microbes= Bacteria, Archaea
Eukaryotic Microbes= Fungi, Algae, Protozoa
When writing the scientific name of a microorganism, the genus is the first name and is always capitalized. The species comes second and is not capitalized. Both names should be underlined or italicized.
Pathogenicity of a microbe- the disease-producing capacity
Resistance of the host- the ability to fight off disease causing microbes
Etiologic agents- the microorganisms and microbial toxins that cause disease in humans. AKA infectious agent
Negative effects of microbes:
Food spoilage
Infectious Diseases of humans, animals, and plants 1. Biological Warfare a. Bacillus anthracis is the etiologic agent of anthrax b. Clostridium botulinum produces many toxins causing muscle paralysis, also used in botox 2. Bacterial resistance to antibiotics
3. Emerging Infectious diseases: new diseases and diseases increasing in incidence (MRSA, West Nile, E. Coli, Avian Influenza A)
Positive effects of microbes: 1. Recycling of chemical elements: microbes are primarily responsible for converting carbon, nitrogen, and oxygen into forms that plants and animals can use. Only bacteria can naturally convert atmospheric nitrogen to a form available to plants and animals. 2. Decomposition of organic matter: sewage treatment; microbes convert leftover liquid and organic materials in sewage into by-products such as CO2, nitrates, sulfates, etc. 3. Bioremediation: microbes can be used to break down or remove toxins from underground wells, chemical spills, etc. Pseudomonas and Bacillus are commonly used. 4. Insect pest control: Bacillus thuringensis is commonly used as a biological insecticide. 5. Food industry: microbes are used to make vinegar, wine, beer, cheese, yogurt, bread, and pickles. 6. Genetic Engineering: production of proteins, vaccines, enzymes, growth hormones, etc. (e.g. Insulin) 7. Gene therapy: use of viruses to carry replacement for defective gene 8. Genomics
Chapter 4
Bacterial shapes:
Coccus- spherical
Bacillus- rod shaped
Vibrio- spiral; look like curved rods
Spirillum- spiral; look like a corkscrew
Spirochaete- spiral; helical and flexible
Hyphal- thread-like
Bacterial Arrangement:
Diplo- pairs
Strepto- chains
Tetrad- clusters of 4, divide in two planes
Sarcinae- clusters of 8, divide in three planes
Staphylo-grapelike clusters or broad sheets, divide in multiple planes
Monomorphic bacteria- maintain a single shape
Pleomorphic bacteria- can have many shapes
Glycocalyx * A gelatinous polymer external to the cell wall and is composed of polysaccharide, polypeptide, or both * The glycocalyx is described as a capsule when the substance is organized and firmly attached to the cell wall * The capsule functions to prevent phagocytosis * The glycocalyx is described as a slime layer when the substance is unorganized and only loosely attached to the cell wall * The slime layer functions to allow cells to attach to diverse surfaces
Cell Wall * Function: prevents osmotic lysis, maintains cell’s rigidity and shape * Bacterial cell wall is composed of peptidoglycan which consists of a repeating disaccharide attached by polypeptides to form a lattice that surrounds and protects the entire cell * Peptidoglycan (PG) is made up of: * N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), which are polymers of the disaccharide portion, “Carbohydrate backbone” * Tetrapeptide side chains- four amino acids attached to NAM’s in the backbone * Peptide cross-bridge- a short chain of amino acids that connect parallel side chains
