3. Bacterial Structure and Function Flashcards
Prokaryotes have no internal/external membranes, single/double chromosomes, no/some histones and no … of gametes
- internal
- single/haploid
- no
- fusion
Bacteria are found everywhere but concentrate at where?
interfaces
Proteins in bacteria are produced where?
cytosol
Bacterial cell length varies from … to …
0.2-700 micrometres
There is lots/little communication between outside and inside bacteria
little
Role of the Gram Stain
- distinguishes between major groups of bacteria
- based on presence of outer membrane in gram negative bacteria
- was the primary identification until more sophisticated methods were available
Difference in cell wall of gram pos and neg - link to gram stain
- pos has thick cell wall of mainly peptidoglycan (retains the crystal violet-iodide complex)
- neg is thinner peptidoglycan and permeable to complex
- neg also has LPS on outer membrane to evade immune response and aid toxicity (o-polysacc varies so immune system can’t detect)
How does penicllin target bacteria?
- acts on peptidoglycan
- bursts cell open
In gram staining, cells are differentiated by colour. What about in Acid-Fast staining and spore staining?
- acid fast is identified with blue and green differences
- spore means cells are red and spores are green to contrast
How does acid fast staining work?
- bacteria with waxy cell walls work well
- carbol fuchsin driven into cells as stain in heat
- destain with 3% acid-alcohol
- high lipid/wax content content means immune response is evaded and requires lots of drugs to target deep in lungs
e.g mycobacterium tuberculosis (TB)
Explain streptococcus pyogenes
- bacteria carried in 5-15% of humans respiratory tract
- acute infections like pharyngitis caused and spread by saliva or nasal secretions
- has a 2-4 day incubation for tonsilitis, fever, headache, lymph node enlargement
The bacterial cytoplasmic membrane is a … …, which is a … barrier … nm
- phospholipid bilayer
- thin
- 6-8
Bacterial LPS can dissociate from bacteria and impacts dentistry how?
- get into water lines
- can colonise here and spread across patients
Bacterial nucleoid is what?
- single chromosome and site of essential genes
- for reproduction and cell division
- defined space in the cell for DNA and not membrane bound
Explain plasmids in bacteria
- circular loop of DNA (non-essential genes)
- replicate independently and can be transferred between cells
- allows bacteria to pick up additional info like antibiotic resistance
- closed and seperate from bacterial chromosomes
Explain flagella
- enable motility through fluid medium in corkscrew motion like propeller
- moves cell away from less favourable areas
- long and thin to rotate (often longer than cell itself)
- used to classify due to diff patterns
- helical structure
- protein is flagellin subunits
Explain peritrichous, polar, lopotrichous flagella
- multiple flagella in diff directions from diff origins of cell
- one flagella
- multiple flagella from the same origin
Rotation of the flagella is coupled to …
the flow of protons across the membrane (proton motive force)
Explain runs and tumbles of bacterial cell
- chemotaxis in bacteria directed by flagella
- runs happen straight towards the good conditions
- intestinal bacteria rely on this to navigate the intestinal wall
- tumbles occur when the flagella rotate clockwise and becomes less coordinated
- flagella unbundle, allow cell to spin and change direction randomly
- after either, the cell can reevaluate and run/tumble again
Explain bacterial fimbriae
- protein filamentous structures
- enable cells to stick to surfaces
- aid biofilm production
Explain bacterial pili
- longer version of fimbriae and less of them
- made of protein to attach but more specialised in pathways
- for adhesion of pathogen to host cells
- allow genetic exchange/conjugation and transfer DNA from donor to recipient
- type IV pili has twitching motility to fire out and connect to external environment and pull cell along
Explain bacterial capsule
- sticky layer of polysaccharide or protein to help with cell adhesion
- no structural strength but is a tight matrix to adhere to cell wall
- slime layer allows easier deformity but buffers against drying out
- extracellular layer between cell and env
Capsule can be stained with what?
india Ink
What is the capsule also called?
glycolalyx
Function of capsule/glycocalyx
- aid adherance/biofilm
- evade phagocytosis
- protect against desiccation
Explain cell inclusions
- packets of energy reserves or building blocks
- safe way to store under osmotic stress
- carbon storage polymers (poly-Beta-hydroxybutyric acid/lipid and glycogen)
- phosphate and sulphur (dynamic and useful reserve)
Explain endospores
- only in highly differentiated cells
- resistant but killed by autoclave
- C.Diff a good example as causes infection in hospital (spores on hospital beds and instruments so hard to eradicate)
Endospores are resistant to …
- dessication
- heat
- alcohol
- changes in new environment
How is spores being highly resistant a good thing?
- spores can be made and then germinate in more favourable conditions
- resistant to the bad conditions and then germinate in better ones
Spores are difficult to eradicate from what?
- contaminated medical material
- food products
