1. general intro to microbio + struc + func of microorganisms Flashcards
LOs
what is microbiology?
4 main types?
- Biology of organisms too small to be seen by naked eye
- TSEs “scrapie-like” agents (Transmissable
Spongiform Encephalopathies - Viruses
- Bacteria
- Eukaryotic microbes: fungi and protozoa
why study microbio?
- Microbes cause most common dental diseases
~ caries
~ periodontal disease - understand infection to enable effective infection + treatment
- By understanding the basic processes of microbes we can dev future treatments
- bacteria Vs eukaryotes Vs viruses1 ~ visible in light microscopes?
2 ~ capable of free growth without another cell
3 ~ cell division makes new cells
4 ~ metabolically active
5 ~ genes separated from cyto by mem
6 ~ genome
BACTERIA EUKARYOTES VIRUSES
1. yes 1. yes no
2. most 2. yes no
3. yes 3. yes n/a
4. yes 4. yes no
5. no 5. yes n/a
6. DNA 6. DNA DNA / RNA
TSEs
- what are they/ stands for?
- affect what? (type of protein)
- how they’re transmitted?
- EGs in humans?
1
- Transmissible Spong Encephalopathies
- group of prions
2
- infective proteins AS they affect struc of other proteins
- proteins then come together to form plaque/ sponge like lesions in brain
- produces progressive condition by affect encephalons of brain & NS
= misfolded proteins
- associated w/ neurodegenerative diseases
3
they’re transmitted by prions
4
- Kuru
- Scrapie
- Creutzfeld-Jacob,
VIRUS FEATURES
- what? (why do antibiotics have no effect)
- how to see?
- genome consists of?
- what do they need to replicate?
1
- small infectious agents
- NOT metabolically active
- can only rep inside cells - antibiotics have NO effect
- can also infect bacteria + archaea - bacteriophage does this
2
- e- microscope
- NOT visible under light microscope (not capable of free growth)
3
DNA or RNA (DS or SS), NOT enclosed in nucleus
4
- host cell - use host cells machinery to rep + reproduce
- obligate intracellular parasites
- only survive in host cell
viral structure
- DNA or RNA genome
- RNA = DS or SS
- RNA can be used directly for transcription by acting as mRNA
- neg RNA needs to be transcribed first (converted to opp strand)
- capsid (protein coat)
- nucleic acid packaged in protein: icosahedral OR helical
how do viruses replicate?
- host cell releases chemotactic cytokines (chemokines) to alert viral cell
- adsorption - it attaches to host cells receptor via the glycoprotein receptor on the viral cell + releases its nucleic acid into host cell
- then undergo receptor mediated cell-cell endocytosis & be stored inside a pinocytotic vacuole (protects cell from antibod)
- uncoating - lysozymes from host cell break down capsid
- virus then uses the host cell’s machinery to produce viral proteins
- virions are then assembled & released by breaking through the cell mem & causing cell lysis in bacterial cells, not so much in animal cells
- reverse transcriptase
- integration
bacteria basic features
- light microscope = visible
- some species = intracellular obligate parasites
- bacteria + eukaryotes
~ metabolically active
~ make new cells via binary fission - no compartmentalisation
-
bacterial structural features?
- membrane lipid bilayer
- singular circular plasmids - contain DNA + have own origin of rep
- plasmids = used to transfer microbial resistance (mini chromosomes)
- bacterial chromosomes combined with several proteins+ RNA molecules = nucleoid (irreg struc)
- ribosomes = translation
- ## cell wall = made of peptidoglycan
how to name bacteria
genus, species + strain
Identification and Taxonomy
strains of bac + viruses = identified + grouped in many ways
how?
- shape and size
- arrangement of growing bacteria
- Gram stain
- culture requirements
- biochemical reactions
- antigenic structure
- nucleic acid technologies
GRAM STAIN DIFFERENTIATION
- defined based on…
- why do they stain in diff ways?
- gram pos Vs neg for gram stain features
1
how they respond to diff strains
2
- stain diff ways as struc of cell wall & outer layers of bac = v diff
- TWO COMMON GROUPS
~ gram pos
~ gram neg - gram stain differentiation
~ stain peptidoglycan cell wall
3
GRAM NEGATIVE
- Remain coloured red or pink as they do not retain the dye when washed
- More resistant to antibodies due to impenetrable cell wall
- Has a cytoplasmic membrane
- Has a thin peptidoglycan cell wall
- Also has an additional outer membrane sitting outside the cell wall
- It contains lipoproteins and a periplasmic space between the bacterial outer membrane and the inner
Cytoplasmic Membrane (Double layer effect)
- The periplasmic space contains specific proteins not found in the cytoplasm
- These proteins are involved in transport, degradation and motility
- Outer membrane is made up of larger outer Lipoprotein Polysaccharides (LPS)
GRAM STAIN DIFFERENTIATION (stain pepridoglycan cell wall)
GRAM POSITIVE
~ These bacteria retain the dye and remain blue
~ Has a cytoplasmic membrane
~ Has a thicker peptidoglycan cell wall
~ Has a slime capsule
~ Has a smaller periplasmic space compared to gram negative bacteria
How is antigenic structure used in identification of bacteria/viruses?
- why
- test
ANTIGENIC STRUCTURE (identification)
- Can be used to identify certain bacteria or viruses by looking at the of antibody-protein interactions
- This occurs because proteins on the bacterial surface are unique to the bacterium
- This test can be done by simple agglutination
- Take a simple
- take a sample of the bacteria required for testing and prepare lots of beads attached with antibodies
- mix the samples together and if they clump together then there has been a reaction
Fungal Structure (components that make up cell wall)
- Fungal cell wall = made of chitin
- Human cell mem contain cholesterol but fungal cell walls contain ergosterol
- On outer wall of fungal cell wall = mannoproteins that help identify fungi (furry, hairy, proteins)
1.Host-parasite relationship
2.What is a parasite?
- Parasites = organisms that live on or on another organism and benefit by deriving nutrients from it
- Parasites are known to cause virulence in host (disease)
- = V complex and unstable situation
