Flashcards in Lab: Microbial Effects Deck (19):
Three primary means by which to control microbial growth:
2. UV light
3. Antibiotics & Antiseptics
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
Spectrum UV light falls in
What makes UV more germicidal?
shorter, higher energy wavelength as compared to visible light or infrared radiation
At what wavelength is UV radiation the most germicidal?
260nm because this is where DNA maximally absorbs it causing mutations
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.
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
Photoreactivation repair mechanism
involves photolyase enzyme the breaks the dimer bonds and rematches the purines and pyrimidines
SOS repair system
enzymatically removes the dimers and inserts new pyrimidine molecules in their place; excision repair mechanism
chemical agent applied to tissue to prevent infection by killing or inhibiting microorganisms
chemotherapeutic agents of low molecular weight that inhibit or kill other microorganisms.
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
SOS repair enzymes
Endonuclease cuts out bad section
DNA polymerase synthesizes nucleotides
Ligase seals Knicks
ion channel disrupter, lipid destabilization, protein interference
yields protein and membrane dissociation
promotes iodination of lipids and protein structure disruption
- inhibits DNA gyrase and topoisomerase IV, yields dsDNA breaks
- natural produced by Actinobacteria
- blocks NAM cross-linking
- primarily used to treat gram + infections