PMI02-2001 Flashcards
What is microbiology?
Biology of organisms too small to be seen with the naked eye
What does TSE stand for?
Transmissable Spongiform Encephalopathies
Which microbes are eukaryotic?
Fungi
Protozoa
What are TSEs?
“Infective” proteins based on the structure of prions but misfolded
Spread their misfolding to form plaques/sponge-like lesions in the brain which are impossible to remove
Where is the genetic information found in bacteria?
Circular chromosome, free-floating in cytoplasm
Plasmids
What is special about plasmids?
Can be passed between bacterial cells
What kind of ribosomes are found in bacteria?
70S
How do bacteria replicate?
Binary fission
Do bacteria have a cell wall?
Yes
What shape are bacilli? Give an example of a bacillus.
Long rods
E. coli
What shape are cocci? Give and example of a coccus.
Balls
Streptococcus aureus
What shape are spirochaetes? Give an example of a spirochaete.
Spiral
B. burgdorferi –> Lyme’s disease
What does a curved bacterium look like? Give an example of a curved bacterium.
Comma
V. cholerae
What shape are streptococci? Give an example of a streptococcus.
Chains of balls
S. pyogenes –> tonsilitis
What shape are staphylococci? Give an example of a staphylococcus.
Clumps of balls
S. aureus
What does the Gram stain show?
Peptidoglycan
What is the difference between Gram-positive and Gram-negative bacteria?
Gram-positive = lots of peptidoglycan in cell wall
Gram-negative = less peptidoglycan in cell wall, has an outer membrane to prevent Gram stain from reaching peptidoglycan
What is a periplasmic space?
Space between plasma membrane and peptidoglycan cell wall
What anchors the outer membrane to the cell wall in Gram-negative bacteria?
Lipoproteins
Is peptidoglycan electron-dense or electron-translucent?
Electron-translucent
What is haemolysis?
Breakdown of red blood cells
What does the α-variant of haemolysis look like?
Red blood cell breakdown only locally/adjacent to cells
What does the β-variant of haemolysis look like?
Larger zone of red blood cell breakdown due to secretion of haemolytic toxins
What does the γ-variant of haemolysis look like?
Very little red blood cell breakdown affecting only cells invaded by the bacteria
How can you classify bacteria? (5)
Shape/size/arrangement
Gram-stain diffferentiation
Colony characteristics
Serotyping/antigens
Genetic sequencing
What colony characteristics can be used to differentiate between types of bacteria? (6)
Morphology and size
Indicator dyes
Surface texture
Nutrients required
Haemolysis
Biochemical tests
What is phage typing?
Bacteriophages recognise different surface proteins on bacteria
Method of differentiating between bacteria
What can be used in genetic typing?
DNA sequencing
RFLP
Probes
PCR
What are the main differences between eukaryotic and prokaryotic cells?
Eukaryotes have membrane bound organelles (inc. mitochondria) and a nucleus/prokaryotes have no internal membranes
Eukaryotes have 80S ribosomes/prokaryotes have 70S ribosomes
Not all eukaryotes have a cell wall/prokaryotes have rigid cell walls
Eukaryotes are larger/prokaryotes are smaller
What is the size range of viruses?
10-200nm
What type of microscope is required to visualise viruses?
Electron microscope
What is the structure of a virus?
Nucleic acid packaged in protein - nucleocapsid
May be naked or enveloped
How do viruses replicate?
- Attach and enter cell (translocation, endocytosis, fusion)
- Uncoats itself within host and exposes genome
- Uses host’s machinery to create more viral components and assembled
- Virus population increases until cell breaks or enveloped viruses can bud off cell
Give an example of an enveloped virus.
HIV
Influenza
Give an example of a naked virus.
Adenovirus
Poliovirus
Bacteriophages
What are the two classes of fungi?
Yeasts
Moulds
How do fungi get their nutrients?
Digestion by extracellular enzymes
In what form do yeasts grow? Give an example of a yeast.
Grow as single cells but can be dimorphic
Candida spp
Cryptococcus spp
In what form do moulds grow? Give an example of a mould.
Grow as hyphae only and produce fruiting bodies with spores
Aspergillus spp
Penicillin spp
Fusarium spp
What is a mycelial network/mycelium?
Mass of hyphae
Describe a fungal cell wall.
Lower layer of chitin sitting on top of the cell membrane
Upper, thicker layer of glucan (β1,3 and β1,6)
Mannoproteins on top
What are hyphae?
Long filaments
What are Koch’s Postulates?
Micro-organism must be present in every case of the disease
Micro-organism must be able to be isolated from the host with the disease and grown in pure culture
Specified disease must be reproduced when the micro-organism is introduced into a healthy, susceptible host
What are commensals?
Harmless, “good” bacteria
Synthesise useful nutrients
How do commensals protect us from pathogens?
Competitive exclusion = pathogens cannot adhere or occupy that niche
What are pathobionts?
Opportunistic microbes existing in normal microbial communities
Under certain environmental conditions become pathogenic
Give an example of a pathobiont.
Candida albicans
Mycobacterium tuberculosis
Salmonella typhimurium
C. difficile
S. aureus
Escherichia coli (hamburger disease)
How can use of antibiotics be bad for our microbiome?
Alters balance of microbe composition and allow growth of pathobionts
What decides the pathogenicity of a microbe?
Virulence genes of microbe
Host factors
What host factors can increase susceptibility to a infectious disease?
Impaired immune system
Hormonal changes
