Microbiology

Question 1

Prokaryotes def:-

Answer 1

Organism group which contains bacteria and fungi, have no membrane-bound nucleus, no double membraned organelles and have circular DNA.

Question 2

Archaebacteria:1

Answer 2

Bacteria which thrive in extreme environments.

Question 3

3 archaebacteria sub-divisions:-

Answer 3

• Methanogenic
• halophilic
• thermoacidophilic

Question 4

Methanogenic archaebacteria:-

Answer 4

Inhabit anaerobic habitats and give off methane as metabolic product. Are responsible for cattle intestinal gases.

Question 5

Halophilic archaebacteria:-

Answer 5

Live in v. salty conditions. Grow in salt concs about 10 times that of sea water.

Question 6

Thermoacidophilic archaebacteria:-

Answer 6

Can live in hot acidic springs where temps may exceed 100oC and pH may be as low as 2.

Question 7

Eubacteria:-

Answer 7

Make up remaining bacteria and are found in all but the most extreme environments.

Question 8

Photoautotrophs:-

Answer 8

Use light energy for nutrition.

Question 9

Chemoautotrophs:-

Answer 9

Use chemical energy for nutrition.

Question 10

Cyanobacteria:-

Answer 10

Photoautotrophs which photosynthesise in a similar way to plants and algae:- co2 +h2o ->(light) carbohydrate + O2

Question 11

4 main bacterial cell shapes:-

Answer 11

• cocci
• bacilli
• spirilla
• vibrios

Question 12

Cocci:-

Answer 12

Singular = coccus

Spherical shape. Come single, in bunches and in chains.

Question 13

Bacilli:-

Answer 13

Singular = bacillus.
Rod shaped e.g salmonella, e.coli.
Come as single and in chains.

Question 14

Spirilla:-

Answer 14

Singular= spirochaete

Spiral shaped sometimes w/tail.

Question 15

Vibrios:-

Answer 15

Comma shaped. Sometimes w/ tail.

Question 16

Bacteria cell wall vs eukaryotic:-

Answer 16

Peptidoglyxan vs cellulose.

Question 17

Bacterial vs eukaryotic DNA structure:-

Answer 17

Single circular strand vs chromosomes (linear)

Question 18

Bacterial vs eukaryotic aerobic resp site:-

Answer 18

Mesosome vs mitochondria

Question 19

Bacterial vs eukaryotic ribosome size:-

Answer 19

70s vs 80s

Question 20

Peptidoglycan:-

Answer 20

Polysaccharide with amino acid side chains. Long straight chains w/ cross linking between molecules:- provides strength, maintains shape and protects against osmotic lysis. NAM and NAG.

Question 21

Bioassay:-

Answer 21

Using living organisms to test the effectiveness of a treatment.

Question 22

Gram staining process:-

Answer 22

Heat fixed bacterial smears stained with crystal violet solution then washed in ethanol, then flooded w/ safranin (counter-stain = red)

Question 23

Gram staining observations:-

Answer 23

Ethanol decolourises gram neg bac whereas gram pos remains violet. Gram pos have thick peptidoglycan walls which bind w/ cv stain. G neg have thin walls containing lipid and polysaccharides, lipid dissolved by ethanol so colour not retained- red colour from safranin.

Question 24

Gram staining medical application:-

Answer 24

G+ can be controllwd quickly by penicillin or penicillin-like antibiotics.
G- are usually controlled more quickly by diff antibiotic type e.g streptomycin.

Question 25

Requirements of bacteria in culture- nutrient media (liquid culture):-

Answer 25

• glucose- energy source, C source for biosynth.
• PO4^- for cell membranes and ATP/DNA/RNA.
• H2O
• Nitrogen:- ammonium, amino acids, NO3^-, urea.

Question 26

Bacteria in culture requirements conditions:-

Answer 26

• suitable temp- microorg dependent (20-40oC, in labs 25oC to avoid human pathogenic bac).
• pH:- slightly alkaline for bac, pH 7.5.

Question 27

Obligate aerobes:-

Answer 27

Require oxygen for growth.

Question 28

•obligate anaerobes:-

Answer 28

Can only survive in absence of oxygen, as oxygen inhibits growth and metabolism.

Question 29

Facultative anaerobes:-

Answer 29

Grow better in O2 press, but can slowly grow without.

Question 30

Binary fission:-

Answer 30

Bacterial growth:- mitosis, asexual reprod.

Question 31

Gram+ vs gram neg cell wall:-

Answer 31

Pos has thick peptidoglycan layer above phospholipid bilayer, neg has thin layer between inner and outer membranes.

Question 32

Methods for counting/quantifying microorganism pop size:-

Answer 32

• Haemocytometer.

* turbidity:-cloudiness of culture, measured w/colourimeter, low transmission of light = high pop.

Question 33

Total count:-

Answer 33

All cells living or dead.

Question 34

Viable count:-

Answer 34

Only living cells, use serial dilution

Question 35

Serial dilution:-

Answer 35

Assume that 1 colony is produced by 1 bacteria. Repeatedly add 1cm^3 of current culture dilution to 9cm^3 of steeile medium and spread 1cm^3 on sterile agar plate until colony no. is just right..

Question 36

Calculating no of bacteria in 1cm^3:-

Answer 36

Count no present and multiply by dilution factor.

Question 37

Why is penicillin more effective in gram pos?

Answer 37

Inhibits peptidoglycan cross-linkage formation in bac cell wall.

Question 38

Aseptic technique for bioassay:-

Answer 38

B4, wipe bench w/ disinf and wash hands. Flame culture bottle neck. Use sterile equipment. Immediately replace lid of petri dish after lifting. Sterilise forceps in bunsen flame.

Question 39

Bacterial growth curve exponential/log phase:-

Answer 39

• rapid cell div.
• no limiting factors.
• cell prod greater than cell death.

Question 40

Bacterial growth curve stationary:-

Answer 40

• pop constant.

* production equal to death.

Question 41

Bacterial growth curve death phase

Answer 41

• pop decreases.
• death>div rate
• lack of nutrients/O2/increase in toxic by-products.