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Lab Exam I
exercises 1-20
| Question | Answer |
|---|---|
| bacteria and archaea do not contain | membrane-bound nucleus |
| bacteria and archaea are | unicellular and microscopic |
| eukarya consist of | fungi (yeast and mold), protozoa, algae, and helminths |
| yeast, algae, and protozoa are | unicellular |
| mold, algae and helminths are | multicellular |
| bioremediation | use of microorganisms to degrade toxic compounds |
| viruses | nonliving entities that multiple within cells of eukarya and prokarya |
| 3 morphologies | coccus (circular), rod, and spiral |
| bright light microscope | visible rays pass through the specimen from a light source in the base of a microscope |
| objective lens | magnifying lens |
| ocular lens | view specimen, further magnifies image |
| monocular light microscope | compound microscope with one eyepiece |
| binocular light microscope | 2 eyepieces |
| light source is located | in base of the unit |
| condenser | collects and converges light rays, light passes through here |
| iris diaphragm | controls amount of light that passes through the specimen |
| objective lenses | 10X (low power), 40X, and 100X (high power) |
| mechanical stage adjustment knobs | allows you to move specimen around the stage for precise viewing |
| coarse adjustment knob | initial visualization of specimen |
| fine adjustment knob | brings specimen into sharp focus once located |
| parfocal | objectives are mounted so that they can be interchanged without varying the focus greatly |
| total magnification | multiply objective magnification by ocular magnification, 10x10=100x |
| dark-field microscope | blocks light rays from being transmitted directly through the specimen is placed in the condensers so light is reflected off the specimen at an angle |
| phase-contrast microscope | living specimens are viewed under this, so that refractive properties are enhanced |
| fluorescence microscopy | specimen is coated with a fluorochrome dye with uv light, specimen emits light of different wavelengths |
| electron microscopy | utilizes beam of electrons, rather than light waves, increasing the resolving power |
| transmission electron microscope (tem) | beam of electrons is directed thru the specimen, visualization of internal structures |
| scanning electron microscope (sem) | visualization of surface details of specimen, beam of electrons is scattered back and forth across surface of specimen |
| carry microscope | with both hands with one on the arm and other supporting base |
| oil must be used to view which lense | 100x |
| endosymbiotic theory | both mitochondria and chloroplasts were once free-living prokaryotes that established a permanent residence in another type of cell |
| saprobe | fungi, derive nourishment from nonliving or decaying organic matter |
| mycorrhizal fungi | provide mineralized nutrients to plant in exchanege for a continuous supply of carbohydrates and other compounds, 90% of plants |
| lichens | provide partner with protection from drying and from UV rays and temperature of direct sunlight, while alga produces organic material that serve as nutrients for fungus |
| hyphae | filaments of mold |
| mold hyphae are divided by cross walls known as | septae |
| aerial hyphae | originate from vegetative hyphae, extend upwards, and support spores |
| vegetative hyphae | grow on the surface of the substrate and absorb nutrients for the mold |
| rhizoidal hyphae | help anchor the mold to the substratum |
| mycellium | mass of hyphae, that are fuzzy, colored growth on damp clothes, food, and rotting fruits and veggies |
| mold cell walls | composed of polysaccharides chitin, cellulose, and glucomannan |
| molds reproduce | asexually by sporulation |
| condiospores | asexual spores borne externally on hyphae on a specialized hyphal stalk |
| sporangiospores | contained inside a sporangium (spherical cell inside) which forms by progressive cytoplasmic cleavage |
| arthrospores | produced by successive fragmentation of vegetative hyphae |
| yeasts reproduce | asexually by budding (new cell develops as outgrowth from older parent cell) |
| sabouraud's dextrose agar | high sugar concentraion and slightly acidic pH (5.6) (growth of mold and yeasts) |
| lactophenol cotton blue stain (lpcb) | used to stain chitin in fungi cell walls |
| protozoa | eukaryotic, unicellular, lack cell wall; known for motility |
| protozoa reproduce with | binary fission (asexual) sometimes sexual |
| apicomplexa | elaborate life cycles and require both vertebrae and invertebrate host |
| schizont | multinucleated asexual form before schizogony (cell division) |
| sporozoites | motile, infective stage that is formed by sexual reproduction within mosquito, circulate thru human body; released when oocytes rupture and migrate into salivary glands of mosquito |
| merozites | migrate to liver and cause liver to rupture, releasing into the bloodstream |
| trophozites | transformed merozites that feed on hemoglobin and kill rbc |
| sporogenic phase | sexual phase of development |
| ookinetes | zygotes that embed into stomach wall of mosquito |
| oocytes | undergo mitosis for 10-20 days |
| ciliophora | covered in cilia (locomotion) |
| algae use | photosynthesis with chlorophyll a |
| marine phygoplankton | major source of world's oxygen//primary producers |
| unicellular algae | found in top of water where light is bright enough for them to carry out photosynthesis |
| colonial algae | groups of algae that coordinate functions like feeding or reproduction |
| filamentous algae | grow long filaments or masses and appear over entire surface of body of water |
| multicellular algae | complex structures that appear similar to plants |
| cellulose, calcium carbonate, silica | compose the cell wall |
| trematodes | bilaterally symmetrical, leaf-shaped, flat, and male/female reproductive organs |
| cestodes | transmitted to humans by eating uncooked, contaminated meat or by ingesting fleas from domesticated animals that are infected with tapeworms |
| tapeworm | parasites the intestines of animals |
| scolex | head of tapeworm |
| proglottids | germinal center that forms new segments |
| roundworms | cylindrical bodies that are tapered at both ends and display bilateral symmetry |
| defined media | nutrient preparations used for microbial growth; exact composition and quantity of each nutrient is known |
| nondefined media | amounts of each particular nutrient may vary from recipe to recipe |
| agar | polysaccharide solidifying agent deruved from marine algae; few organisms degrade it |
| agar slant | liquified medium is allowed to solidify in a test tube at a slanted position |
| agar deep | liquified medium allowed to solidify with tube remaining upright |
| agar pour | liquified medium poured into large test tube and is intended for pouring into a petri plate at a later date |
| agar plate | liquified medium poured into a petri plate in order to create a solid surface for growing bacteria |
| autoclave | sterilizing both media and instruments bc it is both quick and dependable |
| dry heat sterilization | glassware and consist of placing items in hot air oven at 170 degrees for 90 mins |
| filtration | passes thru filter that traps microorganisms while allowing liquid to continue thru filter into sterile container |
| ultraviolet radiation | used in hospitals to sterilize the air or surfaces in a room |
| ethylene oxide | sterilize heat-sensitive materials like plastic petri dishes, cotton packing, and syringes |
| serological pipet | plastic wrapping that must be removed prior to use |
| aseptic technique uses | bunsen burners |
| inoculating loop/needle | passed slowly thru flame, heats will incinerate any organisms that may be present and will sterilize object |
| pure culture | single type of microorganism |
| inoculation/subculturing | transfer a pure culture of organism from one medium to another |
| smears must be | heat-fixed and adhering it to slide |
| simple stains | single dye, show cell shape, size, and arrangement |
| differential stains | two or more dyes |
| gram positive bacteria | 60-90% peptidoglycan, teichoic acids in cell wall |
| gram negative bacteria | few layers of peptidoglycan, 10-20%, outer membrane is asymmetirical bilayer, phospholipds and lipoporoteins and outer leaflet is lipid A |
| gram stain | crystal violet-->gram's iodine-->decolorizer (95% ethanol)-->safranin |
| 10% KOH test | glass slide and thick paste is made, dna causes strings to form |
| acid-fast staining | mycolic acid (60% of cell wall of certain bacteria) |
| endospore | malachite green primary penetrates the tough walls during 10 min incubation step, endospores are green, bacterial cells appear pink |
| essential elements | carbon, oxygen, nitrogen, hydrogen, phosphorus, sodium, sulfur, potassium, chlorine, magnesium, calcium, and iron |
| trace elements | do not need to be specifically added to growth media, present in media components or in water |
| autotrophs | obtains carbon by incorporating the carbon present in atmospheric carbon dioxide |
| heterotrophs | utilize organic carbon as carbon source |
| chemotrophs | energy from oxidation of organic chemicals |
| lithotrophs | energy from oxidation of inorganic chemicals |
| phototrophs | use radiant energy in the form of sunlight as their source of energy |
| chemoheterotrophs | organic chemicals as source of both carbon and energy |
| chemoautotrophs | energy from organic sources and obtain carbon from carbon dioxide |
| photoheterotrophs | sunlight as energy source and organic chemicals as carbon source |
| photoautotrophs | energy from sunlight and carbon from carbon dioxide |
| lithoautotrophs | energy from inorganic compounds and carbon from carbon dioxide |
| lithoheterotrophs | organic chemicals for carbon, utilizing inorganic compounds as source of energy |
| selective media | inhibit growth of some organisms, while allowing growth of other organisms |
| differential media | differentiation bw organisms based on particular metabolic capabilities |
| complex all-purpose growth medium | allow for growth of most microbes under standard incubation conditions |
| colony | single microorganism multiples to form millions of microbes, pile up and then form a discrete visible unit |
| streak plate | separate agar plate into 4 quadrants with wax pencil and transfer bacteria from one quadrant then streaj into small area then streak into next quadrant and repeat; shows physical appearance |
| tryptic soy agar (TSA) | isolates most microbes, allows for growth of wide variety of microorganisms |
| columbia CNA agar with 5% sheep blood | selective and differential medium used for gram positive organisms, includes colisitin (C) and nalidixic acid (NA) |
| B-hemolysis | clear zone in few or no intact rbc, reduced oxygen concentration and inc visibility of reaction |
| a-hemolysis | zone of intact but discolored rbc |
| g-hemolysis | no change is observed in medium around these colonies |
| MacConkey agar | selective or differential medium for gram negative organisms; pink, if no fermentation is translucent |
| mannitol salt agar | selective or differential medium contains sodium chloride and inhibition of halophiles (salt-loving organisms), lower the pH if ferments mannitol, yellow if ferments mannitol, translucent if no fermentation |
| pour plate | isolates bacterial colonies and dilutes different amounts, and grows agar on surface and within the medium, allows to count # of colonies |
| #colonies/ (dilution factor)(volume plated) | colony forming unit |
| spread plate | hockey stick with 95% ethanol with flame then spread over medium |
| pH measures | H ions |
| neutrophiles | 5.5-8.5 |
| acidophiles | 1.0-5.5 |
| alkaliphiles | 8.5-11.5 |
| proteases | breakdown proteins |
| amylases | degrade starch |
| lipases | degrade fats |
| buffers | neutralize acids and help maintain a neutral pH; peptones and amino acids |
| psychrophiles | 0-20 C |
| mesophiles | 15-40 C |
| thermophiles | 45-85 C |
| hyperthermophiles | >80 C |
| superoxide dismutase | prevents accumulation of superoxide radical |
| catalase and peroxidase | breaks down hydrogen peroxide |
| aerobes | grow in presence of oxygen |
| obligate anaerobes | oxygen not required to go thru fermentation or anaerobic respiration |
| facultative anaerobes | can undergo aeroboic/anaerobic respiration or fermentation if oxygen is or isn't present |
| aerotolerant anaerobes | do not need oxygen, undergo fermentation but can breakdown toxic oxygen radicals |
| microaerophiles | require very little oxygen |
| reducing media | chemicals that combine with oxygen to eliminate it from the atmosphere |
| sodium thioglycollate | reduces oxidation-reduction potential of medium |
| resazurin | indicator that shows if the medium has been oxidized, pink if oxidation occured, colorless if stayed anaerobic |
| nonreducing media | incubated under anaerobic conditions |
| gaspak ez gas generating sachets | used with anaerobe jars to generate anaerobic conditions, reduces oxygen concentration in jar |
| water activity | vapor pressure of water in a substance divided by that of pure water at same temperature; relative availability of water within a substance |
| viable when | water is removed but can still grow |
| desiccated | dried out/ dehydrated |
| osmosis | passage of water from high to low concentration |
| osmotic pressure | pressure from different solute concentrations |
| hypotonic | cell swells and ruptures in plasmoptysis |
| hypertonic | cell shrinks in plasmolysis |
| inc internal solute concentrations | pump inorganic ions from environment into cell or synthesize/concentrate organic solute within cell |
| halophiles | salt-loving organisms |
| radiation | transmitted from sun and other natural and man-made sources |
| mutation | change in dna sequence of organism |
| ionizing radiation | x-rays and gamma rays, short wavelengths/ eject electrons from atoms or molecules-->direct damage to cell dna and cause peroxides |
| nonionizing radiation | ultraviolet rays, eerts effects on dna of all cells and causes covalent bonds to form bw adjacent thymine bases |
| dna photolyase | splits thymine-thymine dimers in light repair (photoreactivation) |
| dark repair | involve different enzymes |
| base excision and mismatch repair | activated when slight damage to dna and cus damaged dna out |
| uv radiation | lethal to microorganisms, controls growth in air of hospital rooms, nurseries, and operating rooms; can be used to sterilize materials |
| 5x10^30 microbial cells | on earth |
| microbes present in | water, soil, dust, air, surfaces etc |
| species diversity | measure of community complexity and several different species diversity indices |
| species richness | total number of species found in a community |
| species evenness | relative abundance of each species in a community |
| formites | inanimate objects that harbor microogranisms for a period of time |
| mineral soil | soil in terrestrial environments |
| organic soil | sediment that accumulates in bogs and marshes |
| rhizosphere | zone of growth around roots with dense populations |
| fungi | primary decomposers within habitat, and breakdown highly complex substrates like cellulose, starch, and lignins |
| actinomycetes | gram positive filamentous and/or branching bacteria that decompose complex organic substances, and give soil earthy smell |
| biogeochemical cycling | conversion of inorganic components from one form to another |
| free-living nitrogen-fixing bacteria | high concentrations in rhizosphere |
| symbiotic nitrogen-fixing bacteria | infect roots of leguminous plants like soybeans, peas, alfalfa, beans, clover and peanuts; form root nodules (growths) |
| glycerol yeast extract agar (gye) plus cycloheximide | isolation and enumeration of bacteria in samples w lots of fungi; block translocation in translation |
| indicator organism | presence in sample suggests the presence of another |
| coliforms | aerobic or facultatively anaerobic, gram negative, nonsporing rods that ferment lactose with acid and gas formation within 24-48 hrs |
| standard set | drinking a limit of 1 coliform per 100 ml of water |
| action limit | limit at which action must be taken, 4 coliforms per 100 ml of water |
| membrane filter technique | number of coliforms in a set volume of water |
| m-endo medium | coliform detection medium |
| sodium lauryl sulfate/sodium desoxycholate | inhibit growth of gram positive organisms |
| lactose | differentiates bw coliforms and noncoliforms |
| kf streptococcus agar | detects fecal streptococci |
| fc/fs ratio | number of fecal coliforms divided by number of fecal streptococci; tells whther contamination is of animal or human origin |
| fermentation | microbial growth causes desirable change in a product, like texture, flavor or odor |
| lactic acid-producing bacteria | production of all cheeses, contribute to smells and flavors, higher acidity sharper flavor |
| yeast | added to mixture of flour, salt, sugar, shortening, and water they fermemnt the carbs from flour and sugar to produce carbon dioxide, alcohols, acidic end-products |
| carbon dioxide | trapped in dough and causes dough to rise |
| alcohols and acidic end-products | produce flavors in bread |
| wines result from | fermentation of fruits and yeasts |
| pasteurization | mild heating of beer and wine help prevent spoilage |
| flash method | milk is heated to 72 C for 15 seconds and followed by rapid cooling |
| ultrahigh temperature (uth) | milk is sterilized like this, 74 C to 140 C then back to 74 C in < 5 seconds |
| foodborne diseases | from cross contamination of food processing plants and food with microorganisms |
| foodborne infection | ingests food contaminated by microorganisms |
| intoxication | grow and multiply in a food source and produce toxins that remain in food and which are not destroyed by heating |
| standard methods agar | cultivation and ennumeration of microbes from milk and dairy products, food, and water |
| crystal violet and bile salts | inhibit growth of gram positive bacteria |
| obligate intracellular parasites | viruses multiply within living host cells in a type of symbiosis in which the virus benefits at the expense of the host |
| species specific | presence of appropriate receptors on surface of host |
| bacteriophages | viruses that infect bacteria |
| capsid | surrounds the nucleic acid; sometimes phospholipid envelope surrounds this |
| capsomeres | helical, polyhedral or complex shape capsid subunits |
| lytic cycle | host cell is destroyed once new viruses have been synthesized |
| attachment | tail fibers and plate recognizes a receptor site on bacterial cell |
| entry | inserted thru cell wall of host after tail sheath contracts |
| synthesis | proteins formed |
| assembly | new viral nucleic acid and proteins are assembled into complete virions |
| release | host cells lyse (burst) and new virions are released |
| lysogenic cycle | virus lives in harmony with its host by insertnig its genetic material into host's chromosome |
| viral dna is integrated | and called prophage |
| spontaneous induction | prophage is excised from chromosome and continues thru lytic cycle |
| plaque assay | ennumerate bacteriophage |
| plaque | clear areas when original virus is lysed |
| disinfectants | chemical agents used on inanimate objects to lower the level or number of microbes of surface |
| antiseptics | chemicals used on living tissues to dec number of microbes |
| chemotherapeutic agents | used internally and may be natural or synthetic in nature |
| microbicidal agents | agents that result in microbial death |
| microbistatic agents | cause temporary inhibition in microbial growth |
| selectively toxic | kill or inhibit microbial growth without causing harm to the host |
| modes of action | denature/inactivate enzymes, interfere with structure/function of dna, etc |
| phenolics | disrupt cytoplasmic membranes and denature proteins |
| phenol coefficient | effectiveness of phenol-based antimicrobial agent with respect to phenol |
| alcohol group | ethyl and isopropyl alcohol used to control microbial growth |
| halogen group | iodine, chlorine, bromine, and fluorine; prolonged exposure, sporocial by denaturing proteins |
| oxidizing agents | peroxides, ozone, peracetic acid, sterilize materials |
| surfactants | surface-active agents like soaps and detergents that break thru oily layer of skin (emulsification); then scrub and remove debris |
| heavy metals | can be toxic to humans and can cause allergic reactions, pollution of environment, and microbes can develop resistance to them |
| aldehydes | intense vapors that emanate from preserved specimens |
| gaseous agents | denature proteins and nucleic acids by binding to organic functional groups |
| antibiotics that stop synthesis of cell wall | require bacteria to be actively growing and building new materials with peptidoglycan |
| antibiotica that affect cytoplasmic membrane | disorganize structure of membrane, may produce pores in membrane |
| drugs that target metabolic processes | prokaryotes, halt metabolism of folic acid |
| narrow spectrum | side effects can be prevented |
| broad spectrum | control infection but can have overgrowths of other organisms |
| kirby-bauer test | incubation, antibiotics diffuse into agar and there will be a zone of inhibition if affective, if no zone not affective |
| why aren't you permitted to bring food into the lab? | food can contaminate the experiment and possibly make you sick with other exposed microbes |
| explain the difference bw resolving power and magnifying power of a lens | resolving power lets you see 2 images more clearly, where the magnifying power makes the size of an organism larger for your view |
| what is the advantage of parfocal microscope? | parfocal microscopes stay focused when magnficiation size changes |
| why is oil necessary when using the 100x objective? | oil restricts the amount of light going thru the lens |
| list 5 possible reasons why an object may be difficult to find using a properly working microscope | 1. stage may need to be moved to properly see an organism 2. slide is not properly on stage 3. organism may need a stain 4. 4x lens was not used at start 5. light may not be positioned on organism |
| why are fungi larger than bacteria? | fungi are larger bc they are eukaryotes and contain organelles |
| why do yeasts take longer to grow than bacteria? | yeasts are larger, so their cell division takes longer |
| explain the functions of hyphae in a mold colony | hyphae absorb environmental nutrients and transport them to other parts for use in growth |
| explain difference bw intermediate and definitive host | intermediate host is where parasite first enters its asexual form definitive host is where a parasite reproduces in sexual form |
| explain 2 main contributions of algae | algae make organic molecules like oxygen as a by-product of photosynthesis, and serve as a food source for small fish and invertebraes |
| why should a microbiologist wait until a liquid medium containing agar has cooled to 45 C before pouring the medium into an empty petri dish? | reduce condensation and so organisms can colonize |
| explain why a loop or needle is flamed before it is dipped into a tube containing a pure culture. explain why it is flamed after completing an inoculation | flamed before and after inoculation to limit the possibility of contamination with other molecules and kill other bacterias |
| explain why tubes should be kept as close to parallel as possible to the benchtop while performing any transfers or inoculations | limit air organisms from going into the tubes |
| most microbes cannot be grown by inoculating them into sterile water. explain. what must be provided for organisms to grow? | microbes need nutrients which are not present in sterile water, so they need a culture media |
| in your daily life, you actually utilize aseptic technique in order to minimize contamination. list 5 examples of ways in which you do this | 1. wear gloves 2. wash hands often 3. cover food when storing or not eating 4. hand sanitize after touching contaminated surfaces 5. cover mouth and nose when coughing or sneezing |
| what are the 2 reasons why smears are heat-fixed? | kill bacteria and make sure bacteria stays on the slide |
| what is the purpose of simple stain? | see cell arrangement and morphology |
| in terms of reagents used, what is the difference bw a simple and differential stain? | simple use 1 reagent and differential use multiple reagents |
| the preparation of bacterial smear can be difficult to learn. list 4 reasons why this process may be problematic for some | 1. slide has to fully air dry 2. too much heat used, all bacteria can be killed 3. too much water can overmix smear 4. too little bacteria will not produce strong image |
| what color do you expect cells to be if they are simple stained | loeffler's alkaline methylene blue-->blue safranin-->red crystal violet-->purple |
| what would happen if a student forgot to add the mordant during gram stain procedure | the cells would not retain the purple color and all color would wash off when ethanol is added |
| could bacteria that do not contain cell walls be stained using the gram stain? why/why not? | no bc cell walls contain peptidoglycan, which keeps dye from washing off |
| could a counterstain other than safranin be used? explain | yes bc it could still provide a contrast in color other than purple |
| which step causes poor results in gram stain and why? | decolorization can result in all purple or all red bacteria, bc amount of ethanol used is not exact |
| what is an advantage of using selective media rather than non-selective media? | selective inhibits the growth of different culture, so we can focus on one specific culture. non-selective media has all cultures growing, so it is harder to focus on one culture. |
| why are serial dilutions often needed when trying to determine the number of cfus in a culture? | serial dilutions allow for less colonies to be seen, since they wash them away, which allows us to get a better estimate in couting the number of cfus in a culture |
| what is the purpose of making a streak plate? | allows us to isolate specific colony from other colonies |
| you make a streak plate and find after incubation that all 4 quadrants are completely covered with bacteria, with no isolated colonies. what procedural error may have caused this? | may not have sterilized the inoculating loop long enough, so the previous bacteria were not removed, leading them all to stay in the colony |
| what is the selective criterion of mannitol salt agar? | halophiles |
| two major differences bw prokaryotes and eukaryotes | prokaryotes do not have membrane bound nucleus, eukaryotes do. eukaryotes tend to be larger in size than prokaryotes |
| the ocular lens of your microscope has a magnification of 10x. if you use the 100x objective lens to look at a specimen, what is the total magnification? | 1000x |
| what are the two categories of fungi? | yeast and mold |
| what is the main advantage of electron microscopy as compared to light microscopy? | can view smaller things |
| list 2 pieces of proper lab attire | safety glasses and lab coat |
| the introduction stated that microbes are mechanically separated or diluted over the surface of the medium. how is this accomplished? | divide the plate into 4 quadrants from 1 then spread 2, then 2 to 3, and 3 to 4. Flame inoculating loop each time, which isolates individual colonies to form a pure culture. |
| why is the loop flamed after streaking each quadrant in this technique? | it allows for the culture to become more pure. flaming the loop ensures that it is clean and only a small amount will be spread to the next quadrant |
| what would be the result if a student dipped his/her loop in the stock culture during inoculations of each quadrant? explain | there would be too many cultures to be able to differentiate them, since they would not be diluted |
| what is one advantage of utilizing the pour plate technique over the streak plate technique? | it allows for an approximate count of bacteria present |
| why must the agar pours be cooled to 45 C before use in the pour plate technique? | it minimizes condensation on lids and the bacteria will not be killed |
| explain the consequences if a group removed all the agar pours from the water bath at one time and allowed them to sit on the bench for several minutes before using them | agar cools vey fast and it would no longer be liquid to pour into the plates |
| why can the agar pour tubes be rinsed in the sink after the agar is trasnferred to the petri plate? could you rinse the tubes if the bacteria had been pipetted into the agar pour tubes rather than in the plates? explain | the tubes are not contaminated with bacteria, so they can be rinsed in the sink. if the bacteria was pipetted into the tubes they could not be rinsed in the sink |
| determine the cfu/ml if 0.1ml of 10^-5 dilution is plated and 146 colonies are present following incubation | 146/(10^-5)(.1)= 146,000,000 |
| what is the purpose of the ethanol in the spread plate technique? | it sterilizes the hockey tube |
| why are petri plates used in exercise 7-9 labeled on the agar-containing portion? | they are stored inverted to reduce condensation, so this way we can pick them and see their label with ease |
| explain some safety precautions that must be used when working with ethanol and fire | do not keep ethanol in flame too long, keep the bottle away from the flame and use very little ethanol because the flame spreads easily |
| you inoculate an agar plate with ph 3 with four different bacteria. after incubating at 37C for 24 hrs, you see the result below, which is an acidophile | 2 |
| are there microbes which cause disease in humans considered psychrophiles, mesophiles, or thermophiles? why? | microbes that cause disease are in mesophiles because they can survive in the body temperature. |
| will a facultatively anaerobic microbe contain the enzyme superoxide dismutase? why? | yes bc they can survive in environments with oxygen, which means they are at risk of coming into contact with the toxic forms of oxygen; which are detoxified by superoxide dismutaste, so they will be present in facultative anaerobes |
| a bacterial cell is placed into a solution with drastically lower salt concentration (higher water activity) than in its cytoplasm. what will happen to this cell | hypotonic cell will swell and possibly burst |
| if severe dna damage due to uv radiation occurs in a bacterium, will it be able to repair the damage using base excision? if not, what repair mechanism will it activate instead? | no- sos repair |
| what is the difference bw simple stain and a differential stain? | diff stain distinguished types of cells |
| why is it important to use aseptic technique in the lab? | aseptic technique allows us to be less at risk of contaminating or affecting results, so it is important in the lab |
| you perform a gram stain, and when you view the slide under the microscope, you see a mixture of purple and red cells. what does this tell you about the cells in your smear? | purple means that there are some gram-positive cells and red means that there are some gram-negative cells present in the slide |
| what is the purpose of agar in microbiological media? | solidifying agent |
| how do you properly sterilize an inoculating loop in between uses? | flame w bunsen burner |
| give one reason why microbes are able to be so widespread on earth | microbes are able to be so widespread on earth bc microbes can survive in all different pH, temperature, or uv environments |
| what is a rhizosphere? | plant root associated microbes |
| viruses are obligate intracellular parasites. briefly explain what this term means | parasite that cannot survive outside of a cell, it can only survive inside of a cell |
| why is it important to test water for coliform bacteria | water must be tested for coliform bacteria, bc if there i too much coliform bacteria it can cause harm if ingested or to other microbes if they are placed in the water |
| list 2 ways you can reduce risk of microbial contamination while handling food | washing hands and heating food long enough to kill certain microbes |
| why do microbes differ in the pH required for growth? | different microbes are susceptible to denature in different pH values, so they will range for each microbe so that it can survive |
| how do microbes influence the pH of their own environment? | they either produce acidic or basic waste products, which will change the pH of the environment |
| is boiling water necessarily sterile? why? | no bc heat is not strong enough to free all materials from heat-resistant microbes |
| explain why it is advantageous for an organism to be faculatively anaerobic | produce energy with or wo oxygen |
| explain the difference bw the terms viable and growing and explain how these terms apply to this experiment | viable is when something is able to live. growing is when something inc in size. in this experiment we are looking at live, or viable organisms that may grow or inc in size in the presence of oxygen |
| humans use oxygen in their metabolic processes, so how can portions of the intestines harbor anaerobic organisms? | these organisms do not need oxygen, so they can still survive in these areas, when oxygen is used in processes |
| explain why an anaerobic indicator strip in an anaerobic environment will revert to blue if it gets wet | oxygen is present in water, so the strip will turn blue |
| when plates and tubes are placed in an anaerobe jar, there is no condensation on inside of the jar. however, after the jar is incubated under anaerobic conditions, much condensation is present on the inside of the jar. explain appearance of condensation | hydrogen gas is reacting with free oxygen, which forms water condensation form |
| why is water activity important? | water activity determines the amount of available water for microbial growth |
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