Lab Exam 1 Flashcards
List the parts of the microscope
In descending order:
- Ocular lens - 10x
- Body - transmits image through ocular lans
- Arm - where I hold it to carry it
- objective lens - Magnifies specimen
- stage - hold specimen
- condense - on stage - focuses light though specimen
- diaphragm - controls amount of light through specimen
- illuminator - light source
- coarse focusing knob: larger knob for stage
- fine focusing knob
- base
Describe how you would read a Gram stain
positive - purple - indicated that there is a thicker peptidoglycan wall without the presence of an outer membrane
negative - punk - indicates that there is a thinner peptidoglycan wall with outer membrane
What are some bacterial shapes that we have learned?
cocci - circle rod/bacilli vibrio - curved rod spirillum - rigid spiral spirochete - flexible spiral strep - chain staph - cluster diplo - 2 tetrad - 4 sarcina - cube
How do you read a spore stain? What is a spore
endospore is present if green
endospore - heat and UV resistant, dormant form of cell that can withstand hash conditions
- can turn back into a vegetative cell when conditions stabilize and can then reproduce
What is the starch test used for and how does it work?
starch test - tests for presence of alpha/beta amylase of 1,6 - glucosidase (amylase)
iodine - reacts with starch on plate and turns blue/brown
- if there is a clearing around the growth, it indicates that the organism produces enzymes that break down starch
What is the spirit blue test and how does it work?
tests if microbe has lipase to catabolize fats
- fat in agar - tributyrin oil
clearing around growth indicates presence of lipase
(+) - forms blue precipitate
How does the acid fast stain work and what does it test?
acid fast - using heat, carbolfuchisin can go past waxy mycolic acid layer and get into cell
mycolic acid - found in mycobacterium (ex. TB and leprosy)
What are some examples of prokaryotic and eukaryotic cells? What are their size differences?
Prokaryotic - bacteria and archaea
- 1-5 micrometers
Eukaryotes - Protozoa, yeasts, animals, fungi
- 10-100 micrometers
How do you calculate the length of a microorganism?
at 100x magnification (10x objective) each line = 10 micrometers
at 400x magnification (40x objective) each line = 2.5 micrometers
at 1000x magnification (100x objective) each line = 1 micrometer
How does the Simmon’s citrate agar test work? What is the metabolic process in a positive test?
Tests if an organism is able to use citrate as its only carbon source. Requires citrate permease
citrate gets converted by lyase into oxaloacetate
oxaloacetate gets converted by citrate permease into pyruvate
- also able to convert ammonium phosphate into ammonia/hydroxide - alkalinizes agar and turns blue at pH 7.6
blue - positive - citrate permease present
What does a positive and a negative result look like from a phenol red glucose broth? What does a fermenter vs non fermenter look like?
phenol red - pH indicator - add a single sugar to see if organism is able to ferment that sugar
- add Durham tube - gas formation in some fermentors
red - neutral, unable to ferment sugar
yellow - acidic - able to ferment sugar
gas bubble - gas formation
pink - peptone gets degraded
How does the MRVP test work? What are the results of a neutral fermenter versus a mixed acid fermentor?
MR - methyl red - glucose, peptone, buffer
- tests bacteria’s ability to perform mixed acid fermentation
- overcomes pH buffer to make acid products
- lowers pH and turns red
VP - vogues proskaur
- tests ability to ferment glucose and produce acetoin and 2,3 butanediol - neutral pH
- positive result - red after adding VP - dactyl reacts with peptone and turns red - can perform 2,3 butanediol fermentation
What is the lysine decarboxylase test and what chemical change occurs to the amino acid?
Moeller’s medium - glucose, phenol and bromocresol purple
- add mineral oil on top to promote fermentation
- yellow at acidic, purple at alkaline
- decarboxylation - AA turns into CO2 and amine
- decarboxylation occurs - amine raises pH - turns purple - positive
- yellow - negative
How do you read a EMB plate? What gets fermented?
EMB - selective for coliform, especially E. Coli (sewage)
Lactose gets fermented
Dye in agar prevents growth of Gram positive cells and is selective for coliform
E. coli turns purple/black/metallic green
Entero turns pink
How do you perform a pure culture from mixed culture?
Streak for isolation
- grid in 4 - decreasing density with each quadrant
- flame in between each quadrant
- hopefully have individual colonies by 4th quad
- CFU - colony forming unit - origin of colony
