Microbio Flashcards
What does morphology say about a bacteria, and what are the 3 types of morphology and their key features
Morphology of bacteria dictates their shape, there are 3 types of bacteria:
1. Cocci (spherical bacteria)
2. Bacilli (elongated bacteria)
3. Spiral (helical bacteria)
What does arrangement say about a bacteria, and what are the 9 types of arrangement and their key features
Arrangement of bacteria dictates their way of organisation, there are 9 types of organisation 6 for coccus and 3 main for Bacillia:
1. Pairs (diplococci)
2. Chains (streptococci)
3. Clusters (staphylococci)
4.Single (cocci)
5. Tetrads
6. octet (3d)
- Single (bacillus)
- Pairs (diplobacillus)
- Chains (streptobacillus)
What is hemolysis and what are the 3 types of hemolysis? How does bacteria damage rbc’s and what is the appropriate test?
Hemolysis is essentially the break down of erythrocytes, bacteria produce hemolysisns that damage the membrane of rbc’s. The correct test is cultivating bacteria on an blood agar plate, and judging from their appearance what type and if there is hemolysis. JUDGE HEMOLYSIS ON ISOLATED COLONIES.
- aplha hemolysis
i.e e-coli.
partial hemolysis.
green pigment around bacteria. - beta hemolysis
i.e streptococcus pyogens.
complete hemolysis.
clear zone around colony. - gema hemolysis
i.e staphylococcus epidermidis.
no hemolysis.
nothing around the isolated colonies.
Explain what is differential vs selective media and give 2 examples.
Selective: selective media suppress some and select for other bacteria
Differential: differential media distinguish bacteria from each other.
Blood agar:
Rich in nutrients which means that many species can grow thus not selective
But since hemolysis can be determined due to the rbc’s it is differential
Chapman Agar:
Selective since it contains high amounts NaCl and only few bacteria can survive under its presence (i.e. staphylococcus aureus)
Differential because it is distinguisable for bacteria fermenting manitol since there is a color change.
Due to the acidic product the pH indicator will lower and will make the plate yellow.
What is Gram Staining what is the protocol and its types as well as their characteristics.
Graim staining is a staining method used to classify bacteria into two major groups Gram positive and Gram negative bacteria.
Gram positive bacteria characteristics:
Purple
Thicker Peptidoglycan
No outer lipid membrane
Gram negative bacteria characteristics:
Pink
Thinner Peptidoglycan
Has outer lipid membrane
Protocol:
stain with (blue) crystal violet—-
iodine traps the stain in the bacteria——
wash with acetone (gram+ has thick layer of peptidoglycan and will not be dissolved)——–
red dye safranin to counterstain———
Crystal Violet
Wash
Lugol’s
Decolorize with acetone
Wash
Saffranin
Wash
Dry
How does transfer of genetic material occur in bacteria, give 3 examples.
Transformation
Free DNA from donor cell (i.e lysed bacteria) in the surroundings can be taken up from the recipient cell
Transduction Bacteriophage transfers the DNA from the donor cell to the recipient cell
Conjugation
ie antibiotic resistance to check if A plus L has the ability pass the resistance gene to the other bacterium.
Transfer of genetic material through direct contact using sex pilus.
Give example for type of rods
Most of the time single arrangement but they can also exist in pairs or chains
E.Coli
Clebsiella
Salmonella
Proteus
What is autoclave and what is its most useful feature? Give one example and its stain. FInally what is a endospore.
Autoclave is a machine that uses high temperature and high pressure to ensure that bacteria cant continue to grow and can destroy the endospores.
Sterilization
Normally on high temp is needed can kill bacteria but endospores require autoclaving to be destroyed so they cannot germinate
i.e Bacillus
Induction of endospore formation after stress, the endospores cam lie dormant for many years or becoming reactivated
Malachite green is the endospore stain that is visible as light green for example bacillus has a light pink capsule and a greenish center.
Endospore consist of genetic material surrounded by a thick layer of petidoglycan.
What is the purpose of bacterial structures, give 2 examples and their characteristics.
They give certain characteristics to bacteria
Klebsiella
Viscous sticky and shiny colonies due to its polysaccharide capsule and is also a virulence factor. Virulence factor is described as an ability of an organism to infect the host and cause a disease. Very easy to stain their capsule RED COLOR SURROUNDING WHITE COLOR INSIDE
Proteus
Migrates all over the plate
no discrete colonies
swarming motility due to flagella (moving fast)
Describe what is a fermentation and explain its components and utility. Is there any way we can see everything worked fine in the end?
Used to differentiate different gram- bacteria based on metabolite characteristics. Series of culture tubes that contain different sugars and indicators
KIA tube: Glucose and lactose
-Originally red
-Glucose and lactose acidicyellow
-Glucoseacidicred/yellow
-H2S productionblack/grey precipitate of FeS
Mannitol tube: Fermentation of mannitol
-Originally blue
-positive acidicyellow
-produces gasupside down tube to trap it
Urea tube:
-positive NH3 is formed bright pink
-originally baze agar
Indole/ONPG tube:
-ONPG positiveyellow
(ortho-Nitrophenyl-β-galactoside (ONPG) is a colorimetric and spectrophotometric substrate for detection of β-galactosidase activity.)
-Indole positivered/pink when Kovac´s reagent is added.
(intercellular signal molecule)
-originally clear liquid
At the end a control plate is used to check in case of contamination of the loop with other bacteria and to also check if there the desirable bacteria left at the loop as they should
What is an oxidase test?
What is an catalase test?
Oxidase test
Detects production of cytochrome C oxidases, enzymes which catalyzes conversion of oxygen to water in last step of respiratory chain. The reagent added to the bacterial colony is oxidized by enzymes and blue-purple product is formed. Bacteria possessing oxidases are oxidase-positive and those without enzymes oxidase-negative. Oxidase test is used to identify many species. Pseudomonas and Campylobacter are oxidase positive, other gram-negative rods within this laboratory exercise are oxidase-negative.
Catalase test
Staphylococci= positive. Streptococci=negative.
Catalase is an enzyme used by bacteria to induce the the reduction of hydrogen peroxide into oxygen and water, a positive reaction will produce bubbles of oxygen gas.
What is a bacterial capsule and how can it be stained?
The bacterial capsule is a large structure common to many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily washed off.
Capsule staining: Smear on plate and add capsule stain (india ink)air dry and methanol fixation counterstain with safraninred with clear zone around (capsule).
what are the most common type of media
-There are two main types of media: solid media (agar) and liquid media (broth).
what is basic and what is enriched media?
Basic growth media: EX: tryptone agar
Buffer and nutrients (mostly peptones). Glucose is sometimes added because it is metabolized by most bacteria. If you want a solid medium 1-2% agar is added.
Enriched growth media:
Basic medium + blood + agar. Even the most difficult bacteria will grow.
What is Bile esculin and UTI agar?
UTI (Brilliance)-agar plate:
Contains two chromogenic substrates as indicators that will give the plate different colors depending on which of the two enzymes (or both) is present in the colonies. It also contains tryptophan which gives a brown color if Proteus is present.
Bile esculin agar
Bile salts are selective ingredient and esculin differential.
Bile Esculin Agar is used primarily to differentiate Enterococcus from Streptococcus. Members of the genus Enterococcus are capable of growing in the presence of 40% bile (oxgall) and hydrolyzing esculin to glucose and esculetin. Esculetin combines with ferric ions to produce a black complex.
