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Microbiology Lab
Microbiology Lab Midterm questions
| Question | Answer |
|---|---|
| what is the definition for aseptic technique | an environment or procedure that is free of contamination |
| what is the definition for pure culture | cultures that contain only one bacterial species. |
| what is the definition for mixed culture | more than one type of bacterial species growing on a culture |
| what is the definition for sterile | kills all microorganism's |
| what is the definition for agar slant | test tube containing agar media that solidified while the tube was resting at an angle |
| describe how to sterile forceps | 1.) place ends into Beaker 2" deep with ethanol. 2.) hold end of forceps and pass tips through flame 3 this is repeated 3 x |
| describe how you would hold an inoculating loop and a test tube at the same time. | hold loop in your DOMINANT and the tube in your NON DOMINANT hand cradling the cap with your dominant finger. |
| why is it important to always incubate agar plates upside down. | to prevent the condensation that collects on the top of the agar plate from dripping down unto the culture. |
| why is it important to label agar plates on the bottom and not the lid | 1.) so it won't contaminate the culture 2.) because Petri dishes are incubated upside down to prevent contamination from condensation |
| what is simple staining used for | increase contrast and allow determination of size, shape, and arrangement of cells. |
| described how to make a smear of bacteria on a slide | Page 32 in lab book |
| why is it important to air dry a smear | Water can boil while passing the slide through the flame which could alter the natural shape and size of the bacteria |
| why is it important to heat fix bacteria smeared on a slide | to allow bacteria to stick to slide, it also kills the bacteria |
| what is the basis for how the capsule stain works | pg33 |
| why is it important to not heat fix a slide prepared for a capsule stain | because the capsule is degraded by heat |
| what is the purpose of a spread plate | technique used to see visible and isolated colonies of bacteria that are evenly distributed on the plate and are countable. |
| what is the purpose of a streak plate | made to produce individual colonies of bacteria |
| operating conditions that an autoclave uses to sterilize materials temperature | 120 degrees Celsius |
| operating conditions that an autoclave uses to sterilize materials pressure | 15lbs of pressure or 15psi |
| operating conditions that an autoclave uses to sterilize materials time | 15 mins |
| define sterilization | kills all microorganisms |
| define disinfection | reduction of number of organisms (no threat of disease-causing organisms) on inanimate objects. |
| define antiseptic | reducing organisms on living tissues |
| define contamination | unwanted microorganisms |
| define sepsis | microorganisms in the blood |
| define zone of inhibition | an area on the spread plate that will appear if the disinfectant or antiseptic is effective in preventing bacterial growth |
| how does diffusibility of a disinfectant, antiseptic or antibiotic on an agar plate affect the size of the zone of inhibition. | the solubility, size, viscosity or contraction of these chemicals play a role. |
| what are the steps in gram positive staining | |
| what are the steps in gram negative staining | |
| list some gram negative bacteria | 1.) Treponema pallidum 2.)Borrelia Burgdoferi 3.) Leptospira interrogans |
| list some gram positive bacteria | 1.) Listeria monocytogenes 2.) Streptococcus pnemoniae 3.) Staphylococcus aureus |
| what is differential stain | use two or more dyes to differentiate between cells or structures |
| give examples of differential stain | 1.) gram stain 2.) capsule stain |
| what is meant by the term acid fast bacteria | cell wall is 60% fat (mycolic acid) |
| give examples of acid fast bacteria | 1.) Mycobacterium tuberculosis 2.) Mycobacterium leprae. |
| what genus of bacteria does not have a cell wall | Mycoplasma |
| what would happen to a gram negative bacteria if you left the crystal violet on to long. | they would stain purple |
| what color would gram positive bacteria appear if you left decolorized on too long | gram positive cells will lose the crystal violet and will stain red. |
| what color would gram negative bacteria appear if you didn't decolorize the bacteria | purple |
| what adjectives describe broth culture | 1.) flocculent-clumps 2.) sediment- grow at bottom 3.) pellicle- grow at top rim |
| what technique would you use to isolate a single bacterium from a sample containing many different types of bacteria. | a streak plate |
| if given a DNA sequence can you convert it into RNA or protein | yes |
| what is transcription | DNA to MRNA |
| what is translation | MRNA to protein |
| what enzymes do transcription use | RNA polymerase |
| what enzymes do translation use | ribosomes (proteins) |
| what is meant by codon | 3 nitrogen bases on MRNA |
| what is meant by anticodon | complementary sequences to the MRNA. |
| what does transformation mean | DNA taken up from enviornment |
| what does transduction mean | transfer of genetic material by a bacteriophage (a virus) |
| what does conjugation mean | the transfer of DNA from one bacterium to another |
| what did you do to the bacteria to allow them to absorb the plasmid | The bacteria are given a heat shock, this increases permeability of the membrane |
| what is the structure of the plasmid that you transformed the bacteria with | circular, double chains |
| what is the function of each gene | allows a bacterium to make additional proteins not encoded on the original chromosome. |
| what does it mean to say that bacteria are +PGLO or -PGLO | 1.) +pGLO means the bacteria is resistant to amp. has the ability to glow 2.) -pGLO means the bacteria will not be resistant to amp, will NOT glow * cells that are transformed with the PGLO plasmid will possess the gene for GFP. |
| which bacteria would glow +PGLO or -PGLO when placed onto different media composition. | +pGLO |
| describe how to sterilize inoculating loops | 1.) Hold til Red Hot. 2.) Flame from handle 2 tip |
| how can you prevent particle aresols when sterilizing in open flame | heating the loop shaft until the sample has been heat dried before flaming the loop |
| why are capsule stains special | 1.) capsules do not stain well 2.) the bacterial cell and the slide background are stained instead. |
| how will the capsule appear in the capsule stain | as a halo around bacteria |
| in the capsule stain what will you see overall | 1.) the bacteria will be stained red with a clear halo around them. 2.) the background will appear dark blue |
| what does the gene GFP mean | the bacteria can glow. |
| what is the definition for colony | a visible growth of bacteria that arises from a single bacterium or group of the same bacteria. |
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marquita212086