WEEK 3 - Microbiology Flashcards
What are microorganisms?
- Organisms too small to be seen with naked eye
- Largest group of organisms
- Occupy every conceivable environment
- Most beneficial
What are the two types of microorganisms?
- Cellular organisms
- E.g. Bacteria, Archaea and Fungi, protists, helminths
- Acellular infectious agents
- E.g. Viruses and Prions
What is bacteria (and archaea)?
- Prokaryotes
- They lack internal membranes such as a nuclear membrane around their DNA
- Human, plant, fungi, protists and helminths cells are eukaryotes because their DNA is enclosed in a nuclear membrane
What is nomenclature?
- Have a two-part scientific name, consisting of a genus and a specific descriptive name
- e.g., Escherichia (genus) coli (species)
- Both words spelt out in full when first used
- After that the genus may be abbreviated = E. coli
- Name italicized
What is the structure of bacteria and archaea?
- Unicellular
- One linear or circular chromosome (nucleoid)
- Most have a cell wall and glycocalyx
- Everywhere sufficient H2O
What is diplo?
pairs
What is strepto?
chains
What is staphylo?
clusters
What is the bacterial cell wall?
Rigid structure outside plasma membrane to resist dehydration (shrinking) or swelling (bursting)
What is the two main types of bacterial cell wall?
- Gram–positive
- Gram–negative
What is gram-positive?
- Stain purple
- Thick peptidoglycan layer (sugars linked by amino acids)
- Sensitive to penicillin and lysozyme
What is gram-negative?
- Stain pink
- Thin peptidoglycan layer
- Additional outer membrane (phospholipids and lipopolysaccharides (endotoxins)
- Not sensitive to penicillin and lysozyme
What are other bacterial features?
Glycocalyx
What is flagellum?
Move by flagellum (one or more)
What is fimbriae?
Communicate and stick by fimbriae (many)
What is sex pilus?
Share DNA through sex pilus
What is reproduce rapidly?
binary fission: ~10 min
What is endospore?
Formed within mother cell
What are the prokaryotic requirements?
- Water (80% H2O)
- Energy source
- Suitable pH, temperature
- Aerobic and or anaerobic
- Grow best in dark e.g., No Ultraviolet light
What are viruses?
- Most very small
- No plasma membrane, cytosol or organelles
- Require host cell to reproduce (e.g., animal or bacteria)
- Easily spread (weeks in a droplet?)
- Most are bacteriophages (infect / eat bacterial cells specifically)
Viruses in extracellular state?
Extracellular state (virion)
- Nucleic acid (RNA or DNA)
- Protein coat (Capsid), different shapes
- Spikes attach to receptor sites on host
- Some enveloped by phospholipid membrane from previous host cell
Viruses in intracellular state?
Intracellular state
- Capsid removed once in host
- Exists as a nucleic acid
- Uses host ribosomes to reproduce
- Host cell lyses and releases new viruses
What are prions (PrP)
- Infectious agents composed of a single protein
- Mammals contain gene for amino acid sequence of PrP
- Ingestion of prion PrP causes (a) cellular PrP to refold into (b) disease causing prion PrP
Structure of prions (Prp)
- Two stable tertiary (3-D) structures of PrP
- Normal with -helices (cellular PrP)
- Disease-causing with -sheets (prion PrP)
