HTH 245 - Week of 9/12
HTH 245 - Week of 9/12 HTH 245
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This 4 page Class Notes was uploaded by Grace Notetaker on Sunday September 18, 2016. The Class Notes belongs to HTH 245 at James Madison University taught by Dayna Henry in Fall 2016. Since its upload, it has received 10 views. For similar materials see Foundations of Infectious Disease in Health Sciences at James Madison University.
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Date Created: 09/18/16
HTH245 – Week of 9/12/2016 Chapter 4 - Bacteria Cell shapes and patterns o Bacilli - rod-shaped o Cocci - spherical Diplococcic - pair of cocci Streptococci - chain of cocci Staphylococci - looks like a bunch of grapes o Spirilla - spiral-shaped Spirilla - rigid helix Spirochetes - flexible helix Vibrios – comma-shaped curve rods o * remember: microscopic determination of shape and pattern (morphology) is often the first step of identification Naming Bacteria o Binomial nomenclature genus (capitalized) species (non-capitalized) o some bacteria are named after scientists who discover them, their habitat, shape, associated disease, or a combination o *bacillus – can be descriptive or a genus (all bacteria in the genus bacillus are rod-shaped, but not all rod-shaped bacteria are in the genus, bacillus) Anatomy of Bacterial Cell o Envelope – Capsule – not integral to the life of the cell; can promote virulence (capacity to produce disease); presence of capsule interferes with phagocytosis; “slime layer” Cell Wall – characteristic of ALL bacteria; rigid, corset-like; makes cell resistant from inward diffusion of water (avoiding lysis) Gram-positive: stain purple; stay purple after alcohol dehydrates backbone layer Gram-negative: stain purple; alcohol dissolves outer layer of lipopolysaccharide bilayer, creating holes for violet iodine to diffuse outward through; appears colorless o fig. 4.3 both g + and – have cell walls composed of peptidoglycan o only g – outer membrane external to peptidoglycan (makes cell more virulent – releases endotoxin during lysis) Cell Membrane – passage of molecules between the bacterial cell and its external environment; selectively permeable; double-layered with pores and transport molecules Cytoplasm – part of the cell enclosed within the cell membrane; holds many organelles Nucleoid – DNA-rich area (no nuclear membrane) o Most bacterial cells contain a single chromosome – circular, double-stranded stretch of DNA Plasmids – small circular molecules of nonchromosomal DNA; located in cytoplasm but are independent of chromosomal DNA o plasmids can be transferred from one bacterial cell to another (aka infectious agents) o plasmids can carry genes that confer with antibiotic resistance (aka R (resistance) factors) Spores – extremely hardy structures that are highly resistant to heat, drying, radiation, and a variety of chemical compounds; used in (asexual) reproduction o Vegetative cell – spore-producing bacteria w/ no spores (initiating by adverse conditions) Appendages Flagella – motility; composed of protein, flagellin; found on some bacilli and cocci Pili – adhesion; composed of protein pilin; present in many g – cells; shorter, straighter, and thinner than flagella Bacterial Growth o In unicellular organisms, growth = multiplication o In multicellular organisms, growth = increase in size; multiplication = increase in number of organisms o System of checks and balances limits population size Abiotic factors: availability of oxygen, temperature, and water Biotic factors: suitable habitat, predator-prey relationships, and competition o Growth curve = graph that shows the rate of population growth in bacteria 2 Phase I: Lag Phase “get ready for growth” stage – represents time of adaptation to the new environment (also occurs in infection) might be a slight drop Phase II: Exponential (Logarithmic) Phase Explosion of growth governed by the generation time (time it takes a cell to undergo binary fission) o At conclusion of generation time, population doubles Phase III: Stationary Phase Competition for depleting substances such as nutrients and oxygen Binary fission continues to occur, but at the same rate as the death rate Phase IV: Death Phase Adverse conditions become more pronounced This is when spores will form on spore-forming bacteria, giving it a chance for survival Culturing Bacteria o The purpose of obtaining bacteria (from a throat swab or urine sample) is to grow it so it can be identified o Put the sample in a tube of liquid nutrients and then put onto a petri dish containing nutrients and agar Agar allows production of colonies with recognizable and identifiable properties Also use gram stains and antibiotics to identify bacteria Oddball (Atypical) Bacteria o Mycoplasmas No cell wall “smallest of the small” Mycoplasma pnuemoniae causes walking pneumonia o Chlamydiae Slightly larger then mycoplasmas, can be seen with a light microscope Coccoid Obligate intracellular parasites 3 Transmission from person to person Causes: urethritis, trachoma, lymphogranuloma o Rickettsiae Rod-shaped Largest of the three “oddballs” Transmitted through mosquitoes, ticks, fleas, lice, and other arthropods (except Q fever) Obligate intracellular parasites i.e. Typhus Fever 4