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MCB 3020
Lab Midterm
| Term | Definition |
|---|---|
| mag(total)= | mag(objective: 4x,10x,45x,100x(oil)) * mag(ocular(10x)) |
| microscope framework | arm, base structural parts of the microscope which support the basic frame |
| stage | holds the slide. the mechanical stage clamps the slide and moves the slide around the stage |
| oil immersion | uses oil with approximately the same refractive index as glass to prevent light loss due to diffraction (bending of light rays) which would occur if light traveled from one refractive index to another |
| as magnification increases | the working distance (distance between the object on the slide and the objective lens, when in focus) decreases |
| condensor | directs light towards the objective lens in bright field microscopy |
| iris diaphragm | adjusts the diameter of the cone of light so that it just fills the objective lens |
| as you close down the diaphragm | the light intensity decreases, contrast improves, depth of field increases, limit resolution (with oil immersion lens) |
| resolution (resolving power) = d | the smallest distance between two objects which can be seen as separate; the diameter of the smallest resolvable object; lambda/(2NA) |
| to improve resolution, lower d | d can be decreased by lowering lambda or increasing the NA |
| cocci | spherical shaped |
| bacilli | cylindrical shaped |
| helicoidal | spiral shaped |
| diplococci | divine in one plane; pairs |
| streptococci | divide in one plane; chains |
| staphylococci | divide in three planes irregularly; bunch of grapes |
| tetracocci | divide in two planes; square |
| sarcinae | divide in three planes regularly; cube |
| coccobacillus | very short and almost appear spherical, but they are just slightly longer in one direction than the other |
| fusiform bacilli | tapered at both ends, appearing like a football |
| filamentous bacillary forms | grow in long threads |
| dyes | organic compounds containing a chromophore with affinity for cellular material |
| catatonic dyes | basic dyes, positively charged chromophore; methylene blue, crystal violet |
| anionic dyes | acidic dyes, negatively charged chromophore; acid fuschin, congo red, nigrosin |
| fat soluble dyes | no charge, sudan black granules of Poly-B-OH-butryic acid |
| insoluble dyes | water insoluble, india ink (colloid suspension of carbon particles) |
| negative staining | stains background not cell; two dyes used: nigrosin (black anionic dye; repelled by the negatively charged surface of bacteria) india ink (insoluble dye that does not penetrate the cell surface); used for cell size and morphology |
| simple staining | one dye used to stain all cells the same color; can be used to tell morphology and size (negative staining is better for this); cationic dyes are attracted to the negatively charged surface of bacteria; methylene blue and crystal violet |
| differential staining | causes cells to stain differently based on cell properties; |
| gram stain | gram + have a higher peptidoglycan and lower lipid content than gram - cells; stained with crystal violet then fixed with iodine forming a crystal violet-iodine complex; decolorized with ethanol; counterstained with safranin; g+=purple; g-=pink |
| acid fast stain | have a high wax content in their walls, which requires steam to force dye to penetrate cell; steamed in the presence of carbol fuschin and decolorized with acid alcohol; acid fast remain red; non acid fast are colorless then counterst. with methylene blue |
| two genera of acid fast organisms (all other genera are non-acid fast) | mycobacterium: do not gram stain well if mature because of high wax content within cells, if young appear as gram + tapered walls that sometimes fragment (important species: tuberculosis and leprae); nocardia: acid fast positive organism |
| spore staining | malachite green is steamed into the spores then all other cells are decolorized with water while the free and endospores retain the dye. counterstained with safranin; |
| endospores appear as | green center within a pink sporangium; free spores appear as small green oval bodies; |
| three genera of spore forming organisms | bacillus: aerobic, gram + rod; clostridium: anaerobic, gram + rod; sporsarcinae: cocci |
| five methods of tube media preparation | pour, broth, deep, slant, fermentation broth |
| pour (tube media) | 15-20 ml of liquid agar used to pour into a plate |
| broth (tube media) | 5-7 ml of liquid media |
| deep | 5-7 ml of media which has solidified in an upright position |
| slant | 5-7 ml of media which has solidified at an angled position |
| natural media | media composed of complex raw material whose actual chemical composition is unknown (ex: nutrient agar) |
| synthetic media | media whose exact chemical composition is known and in many instances is designed for isolation, selection, or differentiation of specific types of microorganisms. |
| selective media | a media which favors the growth of one type of microorganism over another. this is accomplished by either inhibiting unwanted microorganisms or enriching conditions towards preferred microorganisms. |
| differential media | a media which differentiates or distinguishes between different types of microorganisms based on differences in appearance of growth or color changes |
| phenylethyl alcohol agar (PEA) | selects for the growth of gram + microorganisms, because PEA is inhibitory to the gram of gram - organisms. |
| desoxycholate agar (DES) | selects for gram - microo. because DES is inhibitor towards the growth of gram + microo.; differentiates for lactose fermenters; lactose fermenters produce acid precipitate the bile salts in the media and absorbs the red dye. |
| eosin methylene blue agar(EMB) | selects for gram - microo; differentiates lactose +/- microo; lactose + show a color change; can differentiate based on amounts of acid produced; purple and pink bullseye: lactose + |
| lactose fermentation in EMB | mixed acid fermenters produce more acid and have dark blue-black centers and some microorganisms like e. coli produce a metallic green sheen; 2,3-butanediol fermenters produce less acid and have pale pink centers and no green sheen |
| blood agar | differentiates microo. baed on their reactions in blood; gamma hemolysis: garbage=no zone of clearing; beta hemolysis: best=complete zone; alpha hemolysis: alright=partial zone sometimes appears green due to partial reduction of hemoglobin in blood |
| biochemical tests | tests used to determine physiological characteristics of microo. particularly in terms of bacterial enzymes and the chemistry of bio-oxidation |
| starch agar | tests for the presence of amylase (hydrolyzes starch to simple sugars); Iodine is added to starch plate and appears blue/black when interacting with starch; if amylase +, there will be a colorless area around the colony |
| milk agar | tests for the presence of enzyme caseinase (hydrolyzes casein, a milk protein, into amino acid products); breakdown in casein cause the milk plate to lose its white color and become clear around caseinase + |
| lipase agar plate | tests for the presence of enzyme lipase (hydrolyzes fat to form glycerol and fatty acids); production of fatty acids lowers the pH just enough to produce a dark blue precipitate when lipase +; indicator is spirit blue |
| sugar fermentation tubes | tests for fermentation of particular sugars; tubes contain the sugar of interest (glucose, lactose, mannitol), pH indicator (phenol red) and Durham tube; |
| sugar fermentation results | if able to ferment the sugar, produces acid which lowers the pH and changes color to yellow from original red color; if makes gas, its trapped in the Durham tube; if alkaline (uses peptone in the broth and not sugar), darkening of the red pH color |
| methyl red (MR) | HCOOH->CO2+H2; tests for mixed acid fermenter; MAF produce drastic amounts of acid from the fermentation of sugars; acid results in the pH dropping below 5.1, so when methyl is red is added, it remains red; if -, then yellow; Escherichia=MR+ |
| voges-proskauer (VP) | HCOOH->acetyl methyl carbinol(acetoin)->2,3 butanediol; tests for 2,3 butanediol fermenter; 2,3BF produce less acid and more neutral products. acetoin is easier to detect than 2,3BF so it tested for with VPI and VPII; |
| voges-proskauer (VP) results | when oxygen is present, KOH will react with acetoin to produce a brick red color and indicate that the microo. is a 2,3 butanedoil producer; alpha-naphthol is used to intensify the red color; enterobacter=VP+ |
| VPI | alpha-naphthol |
| VPII | KOH |
| catalase | converts 2(H2O2) -> 2(H2O)+O2; can be tested by adding H2O2 to the culture and looking for bubbles, if bubbles, then + |
| oxidase | an enzyme which can oxidize aromatic amines to form colored products; tested for oxidase with dimethyl-p-phenylenediamine hydrochloride which when in the presence of oxidase will turn a dark blue/black color |
| nitrate broth | tests for the ability of microo. to reduce nitrate; nitrate 1: sulfanilic acid; nitrate 2: dimethyl-alpha-napthylamine; + if red after nitrate 1 and 2; - if red after zinc; + if never red |
| tryptophan broth (indole) | tests for enzyme tryptophanse which converts tryptophane to indole, pyruvic acid and ammonia; indole can be tested with kovac's reagent (p-dimethylaminobenzaldehyde, amyl or butyl alcohol, and HCl) which will be red ring if + for indole; yellow ring: - |
| urea broth | contains the substrate urea and the pH indicator phenol red; when ammonia is released the pH increases and once above 8.1, the phenol red will appear red;+ appears red; - appears yellow; proteus=urease+ |
| hydrogen sulfide production (H2S) | test for the enzyme cysteine desulfurase which removes the sulfur side chain from cytesine to produce H2S, which when in the presence of iron salts forms a black precipitate; H2S+: black precipitate; proteus: H2S+ |
| SIM | tests for sulfur production, indole, and motility; H2S+ is black precipitate; indole positive: kovac's reagent turns red; motility positive: growth away from inoculation line |
| simmons citrate slant | tests for the ability of a microo. to utilize citrate as the sole carbon source; if positive, growth on the media and media may turn a deep blue color; indicator is bromo thymol blue |
| phenylalanine (PPA) | tests for the presence of the enzyme phenylanase which converts phenylalanine to PPA and NH3; ferric chloride is added to the media, which in the presence of PPA will appear green |
| gelatin | a protein that solidifies at lower temperatures; stab inoculated and then placed on ice for several minutes; gelatinase +, liquid after being put on ice; gelatinase -, solid after being put on ice |
| litmus milk broth | tests for lactose fermentation, reduction of litmus, presence of caseinase, and the deamination of amino acids to produce NH3; contains the pH indicator Litmus and powdered milk; |
| litmus milk results | acid reaction-pink liquid due to drop in pH from ferm. of lactose; acid curd reaction-pink solid due to acid production and coagulation of proteins; reduction-litmus is reduced to be colorless and the tube appears white; |
| litmus milk results, part 2 | alkaline reaction-blue liquid which is caused when protein breakdown produces amino acids that are deanimated and release ammonia; peptonization/proteolysis-clearing of medium (brown or amber) caused by enzyme caseinase |
| IMViC profile | set of four tests that are used to differentiate between escherichia coli and enterobacter aerogenes; indol, methyl red, voges-proskauer, and citrate. e. coli is + for IM and e. aerogenes is + for ViC |
| motility media | tests if the bacteria are motile or not; can contain tetrazolium chloride, a growth indicator which turns red in the presence of growing bacteria, does NOT indicate motility; if tetrazolium chloride is not added to the media, then observe just the line |
Created by:
JacobGant
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