Lab: Microbial Effects Flashcards Preview

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Flashcards in Lab: Microbial Effects Deck (19):
1

Three primary means by which to control microbial growth:

1. Temperature
2. UV light
3. Antibiotics & Antiseptics

2

4 categories of temp. requirements for optimal growth

1. Psychrophiles: min. -5c max. 20c; potimum 10-15c
2. Mesophiles: min. 15c max. 45c; optimum 20-45c
3. Thermophiles: min. 45c max. 85c; optimum 55-65c
4. Hyperthermophiles: min. 55c max. unknown; optimum 85-113c

3

Spectrum UV light falls in

4-400nm

4

What makes UV more germicidal?

shorter, higher energy wavelength as compared to visible light or infrared radiation

5

At what wavelength is UV radiation the most germicidal?

260nm because this is where DNA maximally absorbs it causing mutations

6

What are formed upon absorption of UV light by DNA?

pyrimidine dimers. covalent bond formed between adjacent thymine or cytosine molecules, causing a mutant bulk, disallowing DNA polymerase to replicate past the site.

7

What can protect a cell against UV radiation?

- thick peptidoglycan layer on gram + cells
- outer membrane and thin cell wall on gram - cells
-glycocalyx or slime layer can also protect
- spore formulation

8

Photoreactivation repair mechanism

involves photolyase enzyme the breaks the dimer bonds and rematches the purines and pyrimidines

9

SOS repair system

enzymatically removes the dimers and inserts new pyrimidine molecules in their place; excision repair mechanism

10

Antiseptic

chemical agent applied to tissue to prevent infection by killing or inhibiting microorganisms

11

Antibiotic

chemotherapeutic agents of low molecular weight that inhibit or kill other microorganisms.

12

Kirby-Bauer Method

To determine effectiveness of antibiotics
uses Mueller Hinton agar
wafers with antiseptic/
antibiotic placed in growth on agar
determine size of zone of inhibition
corresponds to minimum inhibitory concentration

13

SOS repair enzymes

Endonuclease cuts out bad section
DNA polymerase synthesizes nucleotides
Ligase seals Knicks

14

Listerine

ion channel disrupter, lipid destabilization, protein interference

15

Bactine

yields protein and membrane dissociation

16

Betadine

promotes iodination of lipids and protein structure disruption

17

Ciprofloxacin

HARD CORE
- inhibits DNA gyrase and topoisomerase IV, yields dsDNA breaks

18

Vancomycin

- natural produced by Actinobacteria
- blocks NAM cross-linking
- primarily used to treat gram + infections
- large

19

Tetracycline

- binds to 30s ribosomal subunit
- inhibits RNA binding, therefore blocking translation
- broad spec. against gram +/-
- can interfere with euk. ribosomes as well