Introduction To Microbes Flashcards
What are the 4 microorganism causing human disease? List them in size order (small to large)
Virus
Bacteria
Fungi
Parasites
What method is used to view bacteria?
Oil immersion microscopy
What are prions?
Proteins (v small) capable of generating copies of themselves
Name types of microorganisms that need a host cell to survive? (4)
Viruses, mycoplasma, chlamydiae, rickettsiae
Why are mitochondria technically a bacteria?
Because they are derived form bacteria
What is the lipid bilayer on the outside of a virus called?
The envelope
What does the protein coat on a virus do?
Protects the genetic material
What type of genetic code does a virus have?
Either DNA or RNA
But not both
What are the spikes on the outside of a virus for?
For attaching to specific cell surfaces
Helps binding to host cells
What are the 3 types of DNA virus classification?
Single-stranded, non enveloped
Double stranded, non enveloped
Double stranded, enveloped
How might enveloped viruses be disprupted?
With chemicals ie alcohol
What is tissue tropism?
the cells and tissues of a host which support growth of a particular viruses.
Some viruses have a broad tissue tropism and can infect many types of cells and tissues.
Other viruses may infect primarily a single tissue
What type of genetic code is found within bacteria?
DNA
How is antimicrobial resistance transmitted between bacteria?
Conjugation
What is a Bacterium’s capsule made of?
Polysaccharides
What is the function of bacteria’s capsules?
Protect against immunological attack
NB:it is possible to find different strains of capsules for the same organisms. Equally so you can find non-capsulated strains of the same bacteria
What is a bacterium’s ‘tail’ called?
Bacterial flagellum
What are the 3 layers of a bacterium surrounding the organism?
Plasma membrane (innermost)
Cell wall
Capsule
What are the projections found on bacteria called?
Pili
What are the 3 bacterial shapes?
Coccus (cocci pl.)-circle
Bacillus (bacilli pl.)-rods (rectangles)
Spirillus- long lines in a wave/spiral
How are bacilli bacteria often found?
As singular isolated cells
What are the 2 types of cocci bacteria arrangements?
Clusters and chains
What is a gram stain?
Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell wall constituents
What are the possible results from a gram stain and how are they identified?
Gram positive (stains purple) Gram negative (stains red)
What does a gram positive result mean for the structure of a bacterium?
The cell wall contains a peptidoglycan layer (external to the plasma membrane and next to periplasmic space)
What does a gram negative stain mean for the structure of the bacterium?
It means there is still a peptidoglycan layer but it is much smaller and there is an outer membrane as well
What types of organisms cannot be identified using a gram stain and why?
Those lacking a cell wall such as mycoplasma
How is a gram stain performed?
- add positive charge crystal violet ( bind to negative cell components- wall proteins)
- add iodine= crystal violet complex if formed. Crystalises dye in cell wall (stops it from being washed out)
(ALL bacterial cells are stained purple)
- add methanol/acetone- removes crystal violet unless cell wall is very thick- thicker wall = less likely methanol/acetone will remove purple crystals
gram-positive organisms retain the stain (stay purple) whereas gram-negative species lose the stain, becoming colourless.
-Add red (safranin) stains to colour the clear, gram-negative, bacteria pink or red
What are the two classifications of bacteria according to their oxygen tolerance?
Aerobes
Anaerobes
What are aerobes?
Bacteria that can survive in the presence of oxygen
What are obligate aerobes?
Bacteria that require oxygen for survival, they absolutely rely on it!
What are anaerobes?
Bacteria that can survive in the absence of oxygen
What is an obligate anaerobe?
Bacteria that requires oxygen free environments to survive, oxygen is ‘poisonous’
In what situation can an obligate anaerobe tolerate oxygen?
If they’re able to form spores
What is a spore?
A dormant form of bacterial life
a rounded resistant form adopted by a bacterial cell in adverse conditions
What are the two types of parasites? What are the difference?
Protozoa (unicellular) and helminths (worms, multicellular)
Give an example of a protozoa parasite
Sarcodina
Give an example of a helminth parasite
Threadworm
Give an example of a yeast fungus
Torula
Give an example of a mould fungus
Acremonium
Give an example of a bacterium
E.Coli
Give an example of a virus
HIV
What are the two classifications of fungi? What is the difference between them?
Yeast (unicellular)
Molds (multicellular)
Why is it difficult to treat fungi?
Because they are eukaryotes and it is difficult to target just the fungal cells and not our own
What is hyphae?
a long, branching filamentous structure of a fungus, collectively called a mycelium
What type of fungi have hyphae?
Molds
What is bacterial pathogenesis?
process by which bacteria infect and cause disease in a host
What is a virulence factor?
Molecules produced by bacteria/fungi/viruses/protozoa that add to their effectiveness and enable them to:
- colonise a host
- achieve immunoevasion
- achieve immunosuppression
- enter and exit cells
- obtain nutrition from the host
Name some virulence factors used by bacteria (4)
- host entry (capsule)
- adherence to host cells (pili)
- invasiveness (enzyme)
- iron sequestration (siderophores)
What two types of toxins are used in bacterial pathogenesis?
Exotoxins and endotoxins
What are exotoxins? Give an example
toxin released by a living bacterial cell into its surroundings (deliberately released by bacteria)
Diphtheria toxin
What is the human papilloma virus associated with? (2)
Warts and cervical cancer
What are helicobacter pylori associated with?
Stomach ulcers
What must a virus have in order to count as a virus?
A capsid/coat of proteins
What are endotoxins? Give an example
Given out during cell death (lipopolysaccharides)
