Control Of Microbial Growth

Question 1

What are the main approaches to microbial growth control

Answer 1

• Physical: non-specific killing/removal
• chemical: non specific or specific, enter certain regions or pathways
• biological: involves biological defends mechanisms
• complex: combination of the above approaches
• environmental: kind of complex approach with addition of control by availability of factors

Question 2

Methods of physical control of microbial growth

Answer 2

Temperature
- low temp growth inhibition, high temp pasteurisation, high pres. high temp sterilisation
Radiation (gamma, X Ray, UV)
Washing up: reduce number of microbes
Filter sterilisation: membranes with pores

Question 3

Methods for chemical control of microbial growth

Answer 3

Cidal agents: natural or synthetic substances that kill microbes like bactericides
Static agents: inhibit microbial growth like chloramphenicol
Lyric agents: substances that lyse cells like penicillin

Question 4

What is MIC

Answer 4

Minimum Inhibitory Concentration needed for complete inhibition of growth

Question 5

Characteristics of disinfectants

Answer 5

Kill microbes but not endospores

- ethanol, cationic detergents, copper sulphate

Question 6

Characteristics of sanitizers

Answer 6

Reduce, but not eliminate, microbes to a safe level outside of the body
- cationic detergents, chlorine compounds

Question 7

Characteristics of antiseptics and germicides

Answer 7

Kill or inhibit microbes: sufficiently non toxic for living tissues
- ethanol, iodine compounds, silver nitrate

Question 8

What is peptidoglycan

Answer 8

Polymer of bacterial cell wall composed by Sugars and AAs, penicillin binds to trans-peptidases (stabilising bonds) to prevent bond formation with oligopeptides
- as a result, penicillin inhibits bacterial cell wall synthesis

Question 9

What is a spheroblast

Answer 9

Bacterial cells without cell wall

- penicillin at low concs allows formation of spheroblasts

Question 10

Name some beta-lactam antibiotics

Answer 10

• Cephalosporins and cephamycins
• penicillin and methicillin

Antibiotics inhibiting protein synthesis interact with Ribosomes E.g. streptomycin inhibits initiation of protein chain

Question 11

Name some antibiotics inhibiting transcription

Answer 11

• Rifampin and treptovaricins (bind to beta-subunit of RNA polymerase)
• Actinomycin (blocks RNA elongation by bonding DNA at guanine-cytosine base pairs)

Question 12

What are the 3 groups of antibiotics produced by bacteria

Answer 12

Aminoglycosides antibiotics
Macrolide antibiotics
Tetracyclins

Question 13

Characteristics of aminoglycoside antibiotics

Answer 13

produced by bacteria- Contain amino sugars bonded by glycosidic linkages and inhibit protein synthesis at the 30S ribosome subunit

Question 14

Characteristics of Macrolide antibiotics

Answer 14

Produced by bacteria - container lactose rings attached to sugar molecules. 11% of world antibiotics production.
Erythromycin, azithromycin, clarithromycin
- inhibit protein synthesis at 50S subunit

Question 15

Characteristics of tetracyclines

Answer 15

Broad-spectrum antibiotics produced by a few streptomycin species. They inhibit almost all bacteria together with beta-lactam antibiotics they are important in medicine

Question 16

What are growth factor analogues

Answer 16

Similarity to important biological molecule like amino acids, vitamins, purines, pyrimidines
- kill rapidly growing microbes by inactivating important macromolecules and processes

Question 17

Give some examples of growth analogues

Answer 17

Sulphanilamide: simplest sulfa drug, blocks synthesis of folic acid and therefore nucleus acids.

Isoniazid: effective drug against TB, interferes specifically with the synthesis of mycolic acid, a cell wall component

Flourouracil and bromouracil: analogs of nuclei acid bases, effective against viral and fungal infections

Quinolones: interact with bacterial DNA gyrase and prevent supercoiling (packaging) of DNA in the cell