Microbiology Lab Test Flashcards

Terms Definitions
Protozoans are (Prokaryotes/Eukaryotes)
Micrococcus roseus
Gram positiveOxidase- positiveBact. temp- a lot of growth in incubator, yellow/green growth at RT
What is culture medium?
Bacteria food
Enterobacter cloacae
Gram negativeBact. O2- obligate aerobe
direct passage of DNA (microbe sex)
Who invented the gram stain?
Christian Gram
What is this cell arrangement? ooooooo
general term for enzymes which hydrolize lipids to glycerol and fatty acids; extracellular
Staph and Strepto are Gram (+/-)
What color appears on a gram negative organism ?

clear to pink
the conversion of nitrate to gaseous divalent nitrogen is called
what genus and species is selected for using TSY20B plate?
The effectiveness of decontamination depends on what seven things?
1.concentration2.time of contact3.gram reaction of the organism4.number of organisms present5.organic contamination of the disinfectant6.object being disinfected7.cost of disinfectant
What lowers the microbial counts to acceptable levels,thus reducing the risk of disease transmission?
The enzyme that breaks the protein CASEIN in milk into its constituent amino acids.
Where do you find facultative bacteria?
Throughout medium
Hektoen Enteric Agar
used to isolate and differentiate Salmonella and Shigella species from other gram negative enteric organisms
Toxoplasma gondii
parasite from feces that can cross the placenta and causes brain damage to the fetus.
All culture media are_______________, _________, or__________.
Liquid, semisolid, or solid.
What is the external appearance of colonies in culture that include form,elevation,and margins?
colony morphology
What is the lens system that is located below the microscope stage that directs light rays up through the specimen?
What are procedures designated by CDC and OSHA for handling body fluid samples?
standard precautions
Selective/differentialfor what? how?EMB
EMB- Eosin/Methylene blue is both differential and selctiveSelective- not perfect does not allow gram +ve againdifferential- obvious (E.coli metallic green)
What color does urea turn if bacteria are acidic in Ureah broth?
What are Bacteria that require oxygen for growth?
Obligate aerobes
What type of bacteria is streptococcus pyogenes? What shape?
Gram positive
What is pleomorphism?
an organism that is demonstrating several different shapes
What are the basic parts of a microscope?




body tube


iris diaphragm

objective lenses

ocular lens

coarse adjustment knob

fine adjustment knob
2 types of immunological rxns
1.) agglutination- where INSOLUBLE antigen complexes with antibodies2.)Precipitin rxns- where soluble antigen and antibodies result in ppt.
At what temperature does the agar solidify?
55 degrees Celsius
What is affected in organisms when a gram stain is applied?
cell wall
What are some moderate resistance organisms?
protozoan cysts,fungal sex spores,viruses
Nitrate reduction test
Possible products are: (red is always terminal)Nitrogen- Air in Durham tube if nitrate is reduced to N2.Nitrite- if after addition of 2 reagents turns red.Nitrate- if Zinc is added and broth turns red, nitrate was never reducedAmmonia- no color change nitrate was never reduced.
What type of medium does starch hydrolysis use?
Starch Agar Plate
What test is used to determine the ability of an organism to split urea to form ammonia by the action of the enzyme, urease. Media also contains the pH indicator phenol red which turns an intense pink at basic pH?
Urease TEst
What type of test uses Phenylalanine Agar?
Phenylalanine deamination test
What is the process of spore staining?
Malachite green-5 minutes
Safranin-20 seconds
Blot dry
What type of bacteria is pseudomonas aeruginosa? What shape are they? Is it aerobic or anaerobic?
Gram negative
Rods (Bacilli)
Microscope that shows dark objects in a brighter field
A brightfield compound microscope
In membrane filtration analysis of water a total coliform count was obtained by using what media?
TCC- all gram negative organismsMedia: M-endo (fuchsin and sodium sulfite) hinders gram positive species.
Hemolysins are capable of what?
Destroying red blood cells and hemoglobins
What is when a urine specimen is not collected using the aseptic technique?
voided urine
what are the gram reaction and morphology of the bacteria? Name a potential species.
Gram -veRod shapedE. Coli
What is Used to determine the ability of an organism to decarboxylate the amino acid lysine,
Lysine Decarboxylase Test
What is another name for the Methyl red test?
Mixed Acid Fermentation
What is a TGYA Shake?
Solid medium to determine oxygen requirements of different bacteria
What is bacteriostatic?
If an agent inhibits the growth of bacterial cells but does not kill them
Pink Coloration on EMB plate
means that there only was small amounts of acid production
3 methods of physically controlling microbial growth
1.) osmotic pressure2.) heat3.) UV light
How do the stabs encourage streptolysin activity?
because of the reduced oxygen concentraion of the subsurface environment
Name two viruses that are the most resistant?
hepatitis b and poliovirus
How does fat hydrolysis work?
Lipase splits fats into glycerol and fatty acids that can be used for anabolism or energy production
Triglycerides + Lipase = Glycerol + 3 Fatty Acids
The medium contains vegetable oil that, when hydrolyzed, lowers the pH
What is the use of a single stain to color a bacterial cell?
Simple staining
What can enhance resolving power?
1) To shorten the distance from the objective lens and the ocular lense. Smaller wavelengths of light improve resolving power.
Conjugation can only occur between
F+ to F- cells. F stands for Fertility Factor. Once a F- recieves the DNA it becomes Hfr (High frequency recombinant) and can now act as a F+ and transfer DNA.
What is blood Agar especially useful for?
Detecting Hemolytic ability of Gram Positive Cocci and as a general purpse growth medium appropriate for fastidious and nonfastidious microogranisms alike
What is the purpose of the kilit ample?
If endospores survive autoclaving, and germinate, vegatative bacilli begin to multiply in broth. In this process, the bacteria uses nutrients within the vial and produce acid.
If given a MacConkey plate where 2 did not grow and 2 others are pinkish red instead of colorless.
MAC is selective:Gram negative organisms will grow, Gram positive organisms will not. This is due to the addition of bile salts and crystal violet.MAC is differential:Lactose fermenters will appear pink, non-lactose fermenters will appear colorless. This is due to the addition of the indicator, neutral red.
What is teh clot formation in the litmus milk test?
Proteolytic enzymes (rennin, pepsin, or chymotrypsin) cause the hydrolysis of milk proteins, which results in the coagulation of milk
How does the gelatin liquefaction test work?
Gelatinase breaks down large proteins into smaller components, which can then enter the organism and be metabolized
What does the use of aseptic technique ensure?
No contaminating organisms are introduced into culture material when the latter are inoculated or handled
What is the name of the thing were you put anaerobic bacteria
GasPak anaerobic jar
The snyder test is a tube containing...
acidic medium and glucose it is innoculated with saliva and the indicator will turn yellow as the microbes ferment glucose. the quicker the fermentation the more likely the patient has dental caries. NOT TRULY ACCURATE.
Which of the following are true of Kirby bauer technique
antibiotics on the dispensed discs are standard concentrations antibiotics are delivered to the bacteria via diffusion(antibiotic testing is determined on Mueller-Hinton plate)
What are three things used to identify a microbe?
1. gross appearance of its growth2. growth requirements of its environment that are necessary for support3.staining properties
What is the procedure for Methyl Red Test and Voges Proskauer test?
Inoculate two MR-VP broths with organism
Incubate at optimum temperature
Add 3-4 drops Methyl Red Reagent
Interpret Methyl Red Test
Pipet 1 ml of culture from other MR-VP
Add 18 drops Barritts Solution A and 18 drops Barritts Solution B
Agitate vigorously for 1-2 minutes
Let stand
Interpret Vogues Proskauer Test
What is teh pour plate method
A method of separating one species of bacteria from another by diluting one loopful of organism into three liquefied nutrient agar plates
What is the ouchterlony plate and what is its purpose?
A plate of agar with wells where antigens and antibodies are placed. The solutions diffuse through the agar and when they meet they either produce a ppt (precipitin rxns) or not. This proves whether an antibody is affective against the antigen placed in a well.
What does e. coli look like on a slide?
Red and pink gram - basillus
When using the GasPak system, to determine oxygen requirement, the strip contains methylene blue is obviously blue until...
no oxygen is present in which case the strip will turn colorless.
How does the nitrate reductase test work?
The reduction of nitrate to nitrite or nitrogen gas takes place under anaerobic conditions in which an organism derives its oxygen from nitrate
NO3 + Nitratase = NO2
NO2 + Nitratase = N2 + NH3
What are the seven steps of acid fast staining?
Cover smear w/ carbolfuchsin- 5 min
Acid alcohol-1 minute
Methylene blue-30 seconds
At the begining of each lab period. Disinfect the _________ top with_____________. Wash hands with _________ and ___________.
At the begining of each lab period. Disinfect the bench top with disinfectant. Wash hands with soap and water.
What are the 2 functions of a capsule?
Does not allow white blood cells to engulf it
Means for bacteria to attach to solid surfaces
How did we analyze food in MCB Lab? was this useful?
First we dilluted the food with water in a blender and plated extracts and counted the number of bacterial colonies. Not really useful because some of the bacteria are supposed to be there (f.e yogurt)
Why is a Durham Tube used in the Carbohydrate Fermentation test?
Captures some of the gas the organism produces, allowing gas production to be seen
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