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Why are microbiology students advised to never eat or drink in the microbiology laboratory?
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Assuming you have a liquid microbial culture (broth culture) that you must dispose of. What are you expected to do with it?
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Micro. 4
Lab test #1
| Question | Answer |
|---|---|
| Why are microbiology students advised to never eat or drink in the microbiology laboratory? | To avoid unnecessary exposure to potential pathogens. |
| Assuming you have a liquid microbial culture (broth culture) that you must dispose of. What are you expected to do with it? | Contaminated culture tubes must be placed in an upright position in the 50- tube basket. They should be capped, and students should aviod spilling them. |
| While working in this labarotory, you will encounter a number of potentially harmful microorganisms. Aside from these, what are some of the hazards associated with work in the microbiology lab? | Bunsen burners, materials that stain, broken glass |
| According to the CDC, handwashing is: | "handwashing is the single most important procedure for preventing noscomial infections". |
| Did thoroughly scrubbing the hands reduce the number and variety of cells present? How do you know? | Yes, as the petri dish shows that most of the organisms were eliminated after hand scrubbing. |
| Did the data you obtained meet your expectations, or did the results differ from what you expected? | Yes, the data showed that hand scrubbing/washing does eliminate organisms on the hands. It also showed that normal flora resides on the tissue even after scrubbing. |
| What type of microscope do we use in lab? | Compound or Bright-field microscope |
| The lens system nearest the specimen that magnifies and produces a real image is called ____, while the eyepiece lens system that magnifies the real image is called____. | Objective lens / Ocular |
| The desired objective is rotated into place by means of a _____. The use of oil decreases the refraction of light rays coming through the observed specimen, thus yeilding greater _____ and a clearer image. | revolving nosepiece / resolution |
| What objective do you use oil immersion on and why? | 100X / Oil on any other lens will interfere with resolution and prevent accurate observation; it can also cause permanent damage. |
| What are the two knobs used for adjustment on the microscope? | Course adjustment / fine adjustment |
| What objective is used when first viewing a new specimen and why? | 4X (scanning) or 10X (low-power) / working distance is great enough that there is no danger of damaging a lens by forcing in into the glass of slides, coverslips or the substance condenser lens. It avoids damage to the prepared slides. |
| What is the significance of calibration? | Calibration allows us to determine the measurement of an object that would otherwise be measured as an unkown incriment. |
| Why must the ocular micrometer be recalibrated for each new objective used? | The magnification of the object changes. |
| What advantage is there to growing microorganisms in broth or liquid media? | Broth media maintains its characteristic shape and arrangement Vs. solid media |
| In broth media this is referred to as a thin coat of cells floating on top of the broth. | Pellicle formation |
| What is agar and why is it an ideal solidifying agent of microbial media? | Agar is a complex polysaccharide produced by marine algae. Most microorganisms do not use agar as a nutrient source, therefore it retains its solidifying effect despite metabolic activity. |
| In what ways do defined media differ from complex media? | Complex media provides necessary nutrients for growth, exact chemical composition is unknown. Defined medias nutrients are in pure chemical form, and the chemical composition is known. |
| Why are the culture media normally sterilized prior to use? | So they are rendered free of any viable cells |
| What is aseptic technique? When do we use it in this labarotory? | Sterility / all the time |
| What is the function of flaming the mouths of tubes prior ro and following incubation? | To keep it sterile, and free of any contamination |
| What is the object of streaking microbial cultures over a broad agar surface? | To obtain one pure culture |
| Why are the Petri plates normally incubated bottom side-up? | To keep colonies forming from growing in one solid mass |
| Where are labels applied to plates containg microbial cultures and why? | On the agar side / to insure cultures can not become seperated from labels. |
| What is a pure culture and what method is most commonly used to obtain a pure culture? | Isolation of a spieces / streak plate method. |
| Which method of streak plate preperation (streak from a broth mixture or directly from a colony on agar) seemed to yeild the best result? What explanation can you give for the variation observed? | Streak plate from a broth mixture, because a pure culture of a single species will usually result. |
| What element is essential to the formation of organic compounds? | Carbon |
| What elements can bacteria pull from the air to make organic compunds? | Nitrogen and carbon dioxide |
| What is the occular micrometer calibration for the 40X, 100X, 450X, and 1000X? | 22, 10, 2.2, and 1 |
| The FORM of whole colonies growing on a solid agar surface may be described as: | punctiform (pin-point), circular, irregular, filamentous, or rhizoid |
| The edge or margin of an individual colony may be described as: | Entire, undulate, lobate, serrate, filamentous, or curled |
| The elevation of a colony may be desribed as: | Flat, raised, convex, pulvinate, or umbonate |
| How do direct stains differ from inderect stains in terms of ionic composition and their interactions with cell surfaces? | Color associated with positive ion (cation), it is a basic stain, color is associated with the negative ion (anion) it is acidic.Cell membranes usually carry a slight negative charge, cells will readily attract and be colored by basic stains or dyes. |
| Why is it important to form bacterial smears by mixing cells with a small amount of liquid and spreading them over a slide surface? | Cells appear seperated from one another. |
| What are two functions of heat-fixing bacterial smears prior to staining? | Heat-fixing makes the cells stick to the surface as well as kills the cells. |
| What is the cell wall made of? Is it found in all cell walls? What is its composition? | Peptidoglycan / no, bacteria does not have peptidoglycan as well as some others. / Peptidoglycan is made up of polysaccharides: N-acetymoramic acid, N-acetyl glucosamine |
| What is a differential stain and when might sucha stain be used? | Gram-stain / this causes different cellls to look different |
| How does the cell wall of a typical Gram-positive bacterium differ from that of a typical Gram-negative bacterium? | Gram-positive = thick peptidoglycan wall Gram-negative = thin peptidoglycan wall |
| What is an important feature of the lipopolysaccharides (LPS) found in association with Gram-negative cell walls? | Toxic to mammilian hosts |
| What is the function of a mordant? | This increases affinity or attraction between cells and causes then to die |
| What would you expect to observe if you forgot to apply a counterstain while making a Gram stain of a Gram-negative bacterial culture? | There would be no color, making the cells unable to observe |
| During a KOH test what do you expect to see with a Gram-negative cell? | The cell will break causing the results to be a slimy material |
| In what ways is the acid-fast stain similar to the Gram stain? | They both make different cells appear different. |
| What is mycolic acid and how does it influence staining? | Wax-like lipid that causes resistance to staining. |
| Are Gram-negative bacteria likely to be acid-fast? | No |
| What would you expect to observe if you decolorized an acid-fast stain preperation with acetone-alcohol instead of acid-alcohol? | nothing, it would remove the cells from the slide. |
| What color do acid-fast cella appear when stained with the acid-fast stain preperation? | blue |
| What are bacterial endospores? | dormant structures |
| What is a sporagium? | spore containing cell |
| What is a glycocalyx? How do bacterial capsules and slime layers differ from one another? | Capsule or slime layer, storage of food, external to cell wall, one is highly organized (capsule), and one is less organized (slime). |
| Describe the size and location of an endospore and a capsule relative to a vegetative cell: | Endospores typically appear as a white area within a darker colored cell, capsules usually have a white capsule surrounding a cell. |
| Why is mordant necessary when preparing flagellar stains? | They increase the diameter making it visiable |
| What is an enrichment procedure or medium? | Specific media or techniques used to promote the growth of certain organisms while inhibiting the growth of others. |
| Can you explain the enrichment procedures usedin this exercise to culture three different genera of bacteria from a single soil sample? | Pseudomonas used a sodium benzoate media, Azotobacter used a fixed nitrogen media (nitrogen free environment), and Bacillus ued a thermoduric media. |
| Were members of the genus Azotobacter the only types of bacteria observed to be growing on the nitrogen-free media? | No |
| Do you think Pseudomonas, Azotobacter, and Bacillus were the only types of bacteria present in your soil sample? Why or why not? | No, because other organisms are able to survive off the same enrichment mediums. |
| What is bioluminescence and what enzymes are associated with this phenomenon? | The ability to glow in the dark using an enzyme known as luciefarase which converts chemical energy into light energy |
| How do cyanobacteria differ from eukaryotic algae? | They have amuch thicker outer membrane. |
| How do the cyanobacteria differ from most of the eubacteria you have been working with in lab? | They are oxygenic and phototrophic |
| Do any of the cyanobacteria you observed display motility? Do they possess flagella? | No, they have fimbriae not flagella |
| What are hyphae? | Thread-like structures that make up the body or thallus of a mold type fungus |
| What are rhizoids? | Horizontal hyphae appearing as short-like branches that attach the fungus to the medium or to surfaces such as glass, they secrete enzymes and absorb nutrients, so are vegitative in function. |
| What are haustoria? | hyphae that penetrate host cells and absorb nutrients. |
| What are mycorrhizae? | specialized hyphae that help the plant obtain minerals and water from the soil. |
| What are conidiophores? | Hyphae that extend away from the culture medium and support spores called sporangiospores, conidiophores are free like like beads on a string. |
| What are the distinctive features of the various phyla of fungi observed? | The slime molds (complex life cycles, resemble protozoa), flagellated lower fungi (live in water have walls of cellulose), and terrestrial fungi (mushrooms, fuff-balls, molds, yeast). |
| The yeasts used in baking (Saccharomyces) belong to which phylum of fungi? | Acomycota |
| If you had a culture of fungi and bacteria, what selective plating procedure could you use to isolate each in a pure culture? | Slide culture/ Mold type fungi will have many of the structures mentioned in this lecture, while yeast type fungi will have few. |
| Which of the algae have motility? What is their mechanism of locomotion? | Dinoflagellata/ they have two flagella which beat within grooves, one transverse(running around the cell) the other lomgitudinal. |
| Which of the algae are unicellular in form? Which are filamentous? | Unicellular: Chlamydomonas, desmids, diatoms, ceratium, peridiniumFilamentous: Spirogyra, ulothrix, oedogonium, cladaphora |
| Which algae contain green chlorpphyll pigments? | Chlorophyta |
| Most protozoa are nutritionally catergorized as ___ but some forms are capable of using light energy and inorganic carbon. Which protozoa often contain chloroplasts and function as photoautotrophs? | Chemoheterotrophs / Euglenozoa |
| Protozoa are single-celled organisms with eukaryotic cells. What types of organelles are readily visiable within or on these organisms? | nuclei, Parabasal body (similar to golgi),flagella, pseudopodia, skeletons, cilia, cytosome |
| In which living form are contractile vacuoles evident? What is their function? | osmoregulation |
| Organisms called Trichnoympha are catergorized within which protozoan phylum? Where were these organisms found? | Archaezoa / found living in the human vagina. |
| Which protozoa have more than one nucleus? | Ciliophora |
| Microscopic invertebrates are similar to protozoa and algae in that they are composed of ___ type cells. | eukaryotic |
| What type of organisms fall into the catergorie generally identified as helminthes? | most are either flatworms (platyhelminthes) or roundworms/nematodes (aschelminthes) |
| Name two general types of flatworms (Platyhelminthes) that are known to infect humans: | Flukes, tapeworms, and freeliving Planaria |
| What is an endoparasite; what is an ectoparasite, and which of the parasite listed falls into each catergory? | Endoparasite live within their host and ectoparasites are external parasites; arthropods such as fleas, ticks, lice and mosquitos |
Created by:
MichelleCheri