Microbiology Flashcards
Describe the DNA in a prokaryote
circular -free in cytoplasm- carries genetic code for proteins.
describe the ribosomes in prokaryotes
-70s
-made of protein and rRNA and is site of protein synthesis/translation.
describe the mesosomes in prokaryotes
folding of plasma membrane.
–site of respiration
describe the cell wall in prokarotes
-made of peptidoglycan/murien- prevents osmostic lysis/bursting.
what is the role of the slime capsule in prokarotes.
protection against drying out and some antibiotics.
role of the plasmid-prokaryote
-circular DNA,
carries genes for antibiotic resistance.
give 6 ways bacteria are identified.
-shape
size
-staining characteristics.
-genetic features
-antigenic features.
- metabolic features.
what is the length of ecoli
3-8 micrometers
why is shape distinguishable between bacteria
is determined by the rigid cell wall which has a unique 3D mesh of peptidoglycan molecules.
why is metabolism distinguishable between bacteria
use different organic molecules as an energy source - some can use other inroganic molecules e.g nitrates.
why is antigenic features distinguishable between bacteria
have unique surface proteins/glycoproteins.
why is genetic features different in bacteria
different codes for different proteins.
why are the staining characteristics between bacteria different
bacteria identified by their ability to take up stain, they are either describes as being gram negative or positive.
what stain is used to stain bacteria
Grams stain e.g crystal violet stain
describe the method for staining bacteria
1.stain cells with cvs (purple)
2.wash cells with solvent (ethanol)
3.gram +ve retain the stain in their thick peptidoglycan wall and appear purple.
4.gram -ve cells lose the stain as their lipopolysaccharide layer is dissolved by ethanol and stain red with safranin a counter stain
name 6 factors that affect the growth of microorganisms
-nutrinets and water
-PH
-temperature
-oxygen abundance.
-type of growth medium
-mineral salts.
how are nutrients supplied to bacteria
in nutrient rich agar or brothe.g a carbon source is supplied for glucose and co2. a nitrogen/ amino acid source is also needed for protein synthesis.
what vitamins are required by bacteria
R, H
what is the usual optimum PH of most bacteria
7.4
what is the term given to bacteria living in acidic conditions
acidophiles.
what are the type of bacteria that grow in high temperatures e.g hot springs
thermophiles
what are the type of bacteria that grow in temperatures of 25-40 c
mesophiles
what type of bacteria grow in very low temperatures
psychrophilic in arctic or Antarctic waters.
what are the three categories for bacteria with different o2 requirements
-obligate aerobes
-obligate anaerobes
-facaultive anaerobes.
what are obligate anaerobes-
cant survive in presence of oxygen. often produce toxins
what are facaultive anaerobes
grow better in oxygen but can survive without but grow much slower e.g e-coli.
