Microbiology Flashcards
What is microbiology?
- Study of things too small to be seen with the naked eye
- Studying bacteria, fungi, archaea and protoza
What are the three domains of life?
Archaea, bacteria, eukaryota
How big are bacteria?
1-6 micrometers
Why can you see some bacteria with the naked eye?
Some accumulate stuff in their vacuole so are larger
What temperature must it be for microorganisms to survive?
Below 140 degrees Celsius
How many human and bacteria cells are in a person?
-10 ^13 human cells
-10 ^14 bacteria cells
How many microbial cells are there on earth?
About 4-6 x 10 ^30
What do archaea produce?
Methane, therefore they are different to others
What conditions do archaea need to grow?
- High temperature
- High pressure
Where are archaea found?
In all soil, they make up 5-10% of the community in the environment. The first archaea was isolated in 2004.
What are fungi?
- Largest organism on the planet
- Largest colony is 10,000 kg
- Size varies
What are protists?
- Most eukaryotes
- Very diverse
- 1-150 micrometers
Why are bacteria and archaea important to us?
- Major portion of biomass on earth
- Key reservoirs of all nutrients of life
Why are there so many bacteria? (5 reasons)
- Rapid growth rate (2x humans)
- Speciation
- Long evolutionary history
- Every niche is occupied
- Lateral gene transfer
What is a phototroph?
Needs energy from light
What is a chemotroph?
Needs energy from chemical bonds
What is an organotroph?
Use organic compounds as electron donors
What is a lithiotroph?
Uses inorganic compounds as electron donors
What is a autotroph?
Uses CO2 as a carbon source
What is a heterotroph?
Uses organic compounds (plants and animals) as a carbon source
What are the primary nutrients that all organisms need?
- Macronutrients
- Micronutrients (trace metals)
What do phototrophs produce?
All 20 amino acids
What are fastidious bacteria?
They cannot produce all 20 amino acids, they need organic components
Where can microbes been grown?
- Eukaryotic cells
- Animals
In what method do bacteria grow?
- Binary fission
- Asexually
- Exponential growth
What stops too many bacteria cells from growing?
Carrying capacity, it stops growth due to limited space and nutrients
How can we measure bacterial growth?
- Turbidimetry
- Haemocytometry
- Dilution planting
- Estimating no. of cells
- Cloudy mediums
What are the 4 phases of bacterial growth?
- Lag phase
- Log phase
- Stationary phase
- Death phase
What is the difference between selective media and differential media?
- Selective media grows specific types of bacteria
- Differential media is based on growth and appearance, it can determine if something is pathogenic
What is a method of enzyme activity testing?
ApiZym - optimised to pathogens
What is the surface origin hypothesis?
There was a warm little pond which had the nutrients for life, there was no o zone layer and therefore hotter
What is the subsurface origin hypothesis?
There are hydrothermal vents at the ocean floor which have more stable conditions which a constant source of energy through redacted inorganic compounds
Which hypothesis for cellular life is more likely?
Subsurface origin hypothesis
What are phylogenies methods used for?
To allow us to determine how related organisms are to each other
What are the two phylogenetic methods?
- Marker molecules (must be universal and in variable and condensed regions)
- Analysing DNA sequencing
How old are eukaryotes?
2.5 billion years old
What are the two theories of evolution of eukaryotes?
- Ancestor of mitochondrion, Nucleus formed, Ancestor of chloroplast (more likely)
- Nucleus formed, Ancestor or mitochondrion, Ancestor of chloroplast
What did early life use as energy?
They used simple compounds (H2 and CO2), and broke down acetate to 2 carbons to produce methane and CO2 using archaea
What did oxygen in the atmosphere do for microorganisms?
Caused them to evolve into a oxygenic photo system using H2O
What are the roles of capsules?
- Carbon store
- Protection against desiccation
- Can capture nutrients
- Stops anti microbial and resist pathogens
What is the difference between a capsule and a slime layer?
- Capsules are organised, tight and not easy to remove
- Slime layers are unorganised, easy to remove, hard to visualise and don’t stop small particles (not well understood)
What is peptidoglycan made of?
Complex sugars (NAG, NAM)
What is the structure of peptidoglycan?
- Mesh like polymer
- Arranged in dimmers (cross linked by amino acids to make amine bonds)
- Strong to retain shape
What is a gram +ve cell wall?
- thicker than gram -ve
- has teichoic acid
- 90% of cell wall (25 sheets of peptidoglycan)
What is a gram -ve cell wall?
- little peptidoglycan
- 10% of cell wall
- between inner and outer membrane
What does penicillin work on and why?
Inhibits PG synthesis during transpeptidation so stops cell wall synthesis meaning that cells lyse.
More effective on gram +ve bacteria
What do lysozymes do?
They degrade 1,4 glycosidic bonds in PG backbone which makes cells sensitive to changes in osmotic pressure which is a defence against bacteria
What is the structure of archaea cell walls?
- no PG/ Meurin
- some have pseudomeurin
- contain polysaccharides, glycoproteins and S layers
- not degrades by lysozymes and not sensitive to penicillin
What do adhesion sites allow?
Transport to outer membrane and outside the cell
What is Braun’s lipoprotein?
- linked to peptidoglycan
- embedded to outer membrane by hydrophobic end
What are archaeal membranes?
- different enzymes used
- structure stabilises membrane at extreme pH and temp
- different to bacterial and eukaryotic
- hydrocarbons are attached to glycerol by ether links
What are the components of the lipopolysaccharide (LPS)?
- Lipid A
- Core polysaccharide
- O side chain
What is the structure of Lipid A in the LPS?
- 2 glucosamine residues linked to fatty acids and phosphate
- integrated to membrane and projects out of cell
What is the structure and function of the core polysaccharide in the LPS?
- can induce an immune response
- side chains of NAG, phosphate and ethanolamine
What is the structure of the O side chain in the LPS?
- variable region
- O serotypes link to disease
- Extends outwards from the cell
- Flexible and bent
- Variable composition
- Rough/smooth depending on chain length
What is the function of the LPS?
- Stabilise membrane
- Reduces permeability
- Protects against host defences (rough more likely to be destroyed)
- Key diagnostic tool
What is the test used to test for endotoxins?
- Rabbit pyrogen test
- LAL assay
What are endotoxins?
- Can cause disease
- Interact with immune system cells and release cytokines
- Toxic in nanograms
- Heat stable
What are porins?
Channels that permit passage of small molecules, water filled channels are in the outer membrane
What are some properties of porins?
- Stable structure
- Thermal stability
- Homotrimeric
- Most are non specific
- Consists of 16 stranded antiparallel beta barrels
What is the periplasm?
The space between the outer membrane and cytoplasmic membrane, works as a protein export. It has a gel like consistency.
What are the two pathways that the periplasm uses?
- sec pathway (folding of protein after translation)
- TAT pathway (exports fully folded enzymes across the membrane)
Name the three types of porters in the periplasm?
- Uniporter (1 in 1 out)
- Antiporter (1 in, diff out)
- Symporter (2 in, 2 out)
What is the structure of flagella?
- rings are anchored to the membrane
- shaft is removed by vigorous shaking
- antigenic properties
- motor driven due to transfer of protons through ring structure
At what speed does flagella move?
300 rpm
What is the order of flagella synthesis?
- MS and C rings connect
- Motor proteins join
- P and L ring, hook and cap
- Growth of filament
Name the 4 types of flagella
- Monotrichous
- Amphitrichous
- Lophotrichous
- Peritrichous
What are the two ways that flagella can move?
- Run (motor goes ACW and filaments bundle)
- Tumble (motor goes CW to twist)
What is aerotaxis?
Movement towards O2
What is chemotaxis?
Movement towards nutrients but away from toxins
What is magnetotaxis?
Movement along lines of magnetism
What is magnetotaxis?
Movement along lines of magnetism
What is phototaxis?
Movement towards light
How does bacteria behave under chemotaxis?
- MCP senses change in environment
- MCP interacts with sensor kinase CheA which can autophosphorylate
- CheA phosphorylates CheY and binding changes the rotation
What is gliding?
Moving without flagella and along the slime layer instead, adhesive molecules move laterally
What is the structure of gas vesicles?
Protein vesicles which contain gas, mainly in planktonic bacteria and archaea
What are gas vesicles used for?
Vesicles fill and empty depending on the needs to move to more oxygenated water or light (buoyancy)
What is the function of fimbriae/ pili?
- involved in genetic exchange between pili
- pull bacteria close to sit on surface to allow penetration of the cell
- allow pathogens to attach
Which types of pili are the most important?
Type I and IV
What is the structure and function of Type I fimbriae?
- Fim F/ G/ H adhesion to fimbriae
- Thin
Works as an export system
What is the structure and function of Type IV pili?
- In gram -ve, in some +ve
- Very thin
- Long
Aggregate laterally to form bundles which have twitching motility
What are sex pilus?
- 1-3 per cell
- Helical arrangement
- Invisible thread
What are sex pilus used for?
They are required for gene transfer and attach via tip, they retract to bring cells together
What are properties of bacterial endospores?
- found in soil
- heat resistant
- only in gram +ve
- 100,000 year life span
- different shapes
- disperse by wind, water and faeces
How are bacterial endospores formed?
Formed inside the bacterial cell when a vegetative cell is stressed
How long does sporulation take to complete?
8 hours (>200 genes involved)
What triggers sporulation?
Nutrient depletion
In what is the peptidoglycan cortex found?
Endospores
Describe the resistance of endospores
- 150 degree resistant
- dehydration prevents denaturation
Describe the 5 steps of germination
1) uptake of H2O and aa triggers germination
2) 30 min process
3) loss of refractile nature as it germinates
4) cell released and grows normally
5) gram -ve on release but becomes gram +ve again
Name 5 barriers to infection
- Lysozymes
- Mucus
- Skin
- pH change
- Flushing of urinary tract
- Acidity in stomach
- Phagocytes
- Blood proteins
- Cilia lining
- Flora
What is the ‘human microbiome’?
The ecological community of commensal, symbiotic and pathogenic organisms that share our body space
What are health benefits of the human microbiome?
1) shield from pathogens
2) produce vitamins by bacteria
What antibiotic was found in 1909?
Arsenic to treat syphilis
What antibiotic was found in 1928?
Penicillin
How many types of antibiotics are there?
5
What did Jenner do?
In 1796 successfully found a vaccine for smallpox by infecting a child with cowpox
What did Pasteur do?
In 1879 found the weakened vaccine
