Microbiology Flashcards
(25 cards)
Classification of Bacteria: SHAPE
Spherical = c…
Rod shaped = b…
Spiral shaped = s…
Spherical Coccus
Rod shaped Bacillus
Spiral shaped Spirillum
Gram Positive Bacteria
Have … outer wall made of … with no outer … layer
which allows c… v… to be … within the cell
Staining the cells …
Thicker
Peptidoglycan
Lipopolysaccharide
Crystal violet/iodine
Retained
purple
Gram Negative Bacteria
Have … peptidoglycan cell wall and an outer … membrane
Cell loses outer … membrane & … walls allow the … stain to wash away
Stains … after … with … - colourless before
Thinner
Lipopolysaccharide
Lipopolysaccharide
Thin
Gram (purple)
RED
Counterstain
Safranin
Gram stain procedure
F..
stain with c… v…
Treat with … solution
D…
… with s…
Fixation
Crystal violet
Iodine
Decolorisation
Counterstain with safranin
Culturing bacteria in laboratory
Conditions:
- c… source - glucose (also gives …)
- n… source for … … synthesis
- g… factors -vitamins & minerals
- suitable p… - most bacteria slightly alkaline (7.4)
- suitable t… - bacterial metabolism regulated by enzymes range (25 degrees optimum)
Different groups depending on oxygen requirements
Carbon - glucose, energy
Nitrogen - amino acid
Growth
pH
Temperature
Bacteria oxygen requirements:
Obligate aerobes
… & … inhibited in … of oxygen
Need oxygen
Growth & metabolism
Absence
Bacteria oxygen requirements:
Obligate anaerobes
… & … inhibited in … of oxygen
Growth & metabolism
Presence
Bacteria oxygen requirements:
Facultative anaerobes
… & … best in … of oxygen, but can respire … if needed
Growth & metabolism
Presence
Anaerobically
Test tube diagram: Oxygen requirements
Clustered at top - need … which … in from air - must be obligate …
Clustered at bottom - away from … source - must be obligate …
Spread throughout but mainly at top - must be f… a…
Oxygen
Diffused
Aerobes
Oxygen
Anaerobes
Facultative Anaerobes
Aseptic Technique
Maintains … and prevents … of e… & b… with unwanted microorganisms
Sterility
Contamination
Environment
Bacteria
Measuring growth
Directly:
T… - count living & dead cells
V… - count living/actively growing cells
Indirectly:
measures … (cloudiness) with …
Gives total count - can’t distinguish between living & dead
Total
Viable
Turbidity
Colorimeter
Viable count method (serial dilution)
Counts cells that are able to grow into visible …
If population too high to count, … with water
To estimate pop in original sample: no. Of colonies x dilution factor
Colonies
Dilute
Viable - underestimate
1) does not include … bacteria
2) cannot be sure it has grown from single … (bacterial cells may have clumped)
Dead
Bacterium
Colony
= cluster of … (clones) arising from single …
Cells
Bacterium
Pathogen
Micro-organisms that causes … in host
Disease
Gram Positive vs Gram negative
Positive - … layer of … in cell wall - binds c… v… - stains p…
Negative - … layer of … in cell wall - … binds … - stains r…
Thicker
Peptidoglycan
Crystal violet
Purple
Thinner
Peptidoglycan
Lipopolysaccharide
Safranin
Red
Advantage gram negative has over gram positive
Less … to … etc.
Extra outer… layer on cell … - more …
Susceptible to antibiotics
Lipopolysaccharide
Wall
Complex
Chemical components of extra outer layer of gram negative bacteria
- L…
- P…
Lipopolysaccharide
Protein
Choosing correct plate
Best choice: … colones - no …
Worst choice:
- too many colonies - … - hard to count accurately
- too few colonies
Distinct
Merging
merged
How colonies develop
[sample] contains …
Each … cell … to produce a …
Bacteria
Bacterial
Divides
Colony
Precautions for aseptic conditions
- … equipment - a… = best
- … workspace
- work near … - u…
- flame n…/m… of bottle
Etc.
Sterile - autoclave
Disinfect
Flame - updraft
Neck/mouth
Why is the no. Of bacteria present only an estimate?
- assumption that one … is produced by one … cell
- does not include the …
Colony - bacterial
Dead
Why might bacteria be cultured at 37 degrees and not 25 degrees?
Experiment to count … bacteria
Which … & … quicker at temp closer to body temp (37)
Pathogenic
Grow & metabolise
Antibiotic against gram positive
1) inhibits formation of c… l… in cell walls
2) wall …
3) … uptake
4) cell wall …- L…
5) kills …
Gram negative walls are protect by layer of …
Cross linkages
Weakened
Osmotic
Breaks - lysis
Bacteria
Lipopolysaccharide
