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Microbiology 290 LAB MIDTERM
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_____ can be used to explore the structures and functions of cells of microbes as well as other entities that cannot be seen with the naked (unaided) eye. - correct answers Microscopes When scientists examine a specimen on a microscopic slide, light passes through the specimen so the lenses _____ or magnifies the image. - correct answers enlarges What are the 4 general "Principles of Microscopy": - correct answers Wavelength of radiation Magnification Resolution Contrast ______ is one part of a spectrum of electromagnetic radiation includes X rays, microwaves, and radio waves. - correct answers Visible light Beams of radiation may be referred to as either _____ or _____. - correct answers Rays or waves All rays/waves differ in _______ (the distance between two corresponding parts of a wave). - correct answers Wavelength Using radiation of smaller wavelengths (i.e. visible light and UV) enhances ______. - correct answers Microscopy
This refers to an increase in the size of an object. - correct answers Magnification It is indicated by a number and "x, x which is read "times" (i.e. 40X) This results when a beam of radiation refracts (bends) as it passes through a lens. - correct answers Magnification This is the ability to distinguish two points that are close together. - correct answers Resolution The better the ______, the better two nearby objects are distinguished from one another. - correct answers Resolution This means the microscope has two oculars or two eyepieces for viewing the specimen. - correct answers Binocular A compound microscope has at least two lenses or mirrors used to produce an image. What is the source of illumination? - correct answers Visible light 4^x is the shortest, _________ objective, used to quickly locate your specimen by viewing a large area of the slide. - correct answers Scanning As magnification increases, smaller portions of the specimen are viewed through the microscope. What is the next longest objective after 4^x? - correct answers 10^x, medium power objective
This is the measure of the differences in appearance between two objects. - correct answers Contrast What is one way we can increase contrast? - correct answers Staining Staining imparts color to the cells, which increases the contrast with the bright background of the light microscope. Another way we can increase contrast is by? - correct answers Adjusting the light At lower magnification, less light is needed for good contrast. The ____ the magnification, the _____ the level of light needed for good contrast. - correct answers Higher, higher The ________ of an image is determined by multiplying the magnification of the ocular by that of the objective lens. - correct answers Total magnification To determine the total magnification when using the scanning objective, you would multiply the power of the ocular by the objective power of the scanning objective to get ____ as the total magnification. - correct answers scanning objective= 4^x ocular= 10^x Total magnification= 40^x This is the circular area we see when you are looking through the oculars of the microscope. - correct answers Field of View It is also defined as the diameter of the viewing field measured at an intermediate plane of angle.
The actual size of the field of view _____ as magnification _____. - correct answers Decreases, increases The higher the magnification ________, the more the field of view _______. - correct answers Increases, decreases Due to the magnification increasing, the size of the specimen that is being viewed (more detail is seen) but less of the actual background _____. - correct answers FOV What can be used to minimize light scattering? - correct answers Immersion oil Oil immersion lens increases _______ because light does not refract. - correct answers Resolution Since light scattering is decreased, the image is clearer and sharper and has better contrast. Immersion oil should be used with the _____ ONLY. - correct answers 100^x These types of microscopes uses fluorescent dyes and uses UV laser to illuminate fluorescent chemicals in a single plane. - correct answers Confocal Microscopy Computer constructs 3-D image from individual digitized images. This type of microscope can be used to view surface features. - correct answers Scanning electron microscope (SEM) This type of microscope can be used to view internal structures. - correct answers Transmission Electron Micrograph (TEM)
This technique is used to distinguish true motility from brownian movement (random jiggling/vibration motion). - correct answers Hanging Drop In this method, a drop of fluid containing bacteria hangs under a coverslip in the well of a depression slide. For many pathogenic bacteria, the ability to move toward targets inside the host is essential to their ability to cause ______. - correct answers Disease Most motile bacteria use ______ to swim. - correct answers Flagella Flagellar movement often causes a "run-and-tumble" phenomenon where bacteria change directions fairly frequently. They're two types of movement: One type is: _____= typically caused when water molecules collide with the cells and make them move. - correct answers Brownian movement They get bounced around like a pinball. The cells oscillate and appear to shake in place (they don't move very far in any particular direction). This is NOT REAL MOTILITY. What is the clinical significance of wet mounts? - correct answers Can be used for diagnostic purposes such as in the case of a vaginal wet mount (a vaginal smear) A vaginal wet mount is a gynecologic test wherein a sample of vaginal discharge is observed by placing the specimen on a glass slide and mixing with a salt solution such as ____________. - correct answers KOH Potassium hydroxide
During the whiff test, dispensing a drop of KOH on a drop of the discharge from a woman with bacteria vaginosis (BV) will result in a "fishy odor" Th KOB kills bacteria and cells from the vagina, leaving only yeast for a yeast infection. Examining ____________ can help distinguish BV from yeast vaginitis (candidiasis) and trichomonas (a type of sexually transmitted infection) - correct answers vaginal discharge This type of smear is used for detection of parasites in the blood. - correct answers Thick Smear A thick blood smear is a drop of blood on a glass slide. This type of smear is used to determine which species of parasite is causing the infection in the blood. - correct answers Thin Smear A thin blood smear is a drop of blood test that is spread across a large area of the slide. Microbes must have a constant _________ supply if they are to survive. - correct answers Nutrient "Lab-grown" microbes must be provided with nutrients using artificial media. Microbes can be grown in various types of media: Liquid media are called ______ Solid media are called _____ - correct answers Broth, agar Any desired nutrients may bee incorporated into broth or agar to grow bacteria.
These types of surfaces provide a larger surface area for aerobic microbial growth while the butt of the tube remains almost anaerobic. - correct answers Slanted surfaces If the tubes are kept vertical until the agar solidifies, they are called? - correct answers Deeps This is used to find out the gas requirements of a microbe? - correct answers Agar deeps After inoculating the agar deep, we can look at the results: If microbe only grows on the surface, it is ______. But microbe can also grow within deep and/or below the surface, it is capable of surviving in ________ concentration. If the microbe is found growing far away from the surface, it means that it grows inn ________ conditions. - correct answers Aerobic, requires oxygen low oxygen Anaerobic To cultivate or culture microorganisms, a sample called an ___________ is introduced into a collection of nutrients. - correct answers Inoculum After an appropriate period of time called ______, colonies develop from each culture. - correct answers Incubation Microorganisms that grow from an inoculum are called a ______. - correct answers Culture This also refers to the act of cultivating microorganisms.
The method of handling microbes and materials in a way that minimizes contamination is called - correct answers Aseptic technique Refers to a set of procedures designed to prevent pathogenic contaminants from contaminating media and experiments. Involves hand washing, PPE, sterile media, and sterilizing tools used for conducting experiments prior to beginning a lab procedure All media, vessels, and instruments must be _____- free of any microbial contaminants to isolate a pure culture. - correct answers Sterile This aseptic technique method involves "flaming" your inoculating loop into the hottest part of the flame (inner cone) of the bunsen burner for three passes prior to placing it into your culture of bacteria and/or media. - correct answers Direct flame method A hot loop will kill your microbes Centers for Disease Control and Prevention (CDC) established a set of guidelines, called _________ - correct answers Universal Precautions First established in 1987 to protect health care professionals from contamination by pathogens when providing health care or first aid. Patient samples will usually contain a variety of microbes of different types, shapes, sizes (due to the variety of natural ______that lives in and on humans). - correct answers Flora As such, culturing patients samples typically results in a mixed culture being grown. Isolation techniques that involve sub-culturing must be conducted to obtain pure cultures which are cultures composed of cells arising from a single ________ (one type of microbe) - correct answers Progenitor
Eosin, methylene blue, and crystal violet dyes as well as bile salts may be included in media to inhibit growth of gram-_____ bacteria without adversely affecting gram-______. - correct answers Positive, negatives This type of agar is also selective, as it contains antibiotics that inhibits the growth of bacteria, thereby helping to support the growth of fungi. - correct answers Sabouraud This type of media helps to differentiate one type of microbe from others growing on the same agar. - correct answers Differential Such media take advantage of the fact that different bacteria utilize the ingredients of any given medium in different ways. The differentiation is based upon the microbe's biochemical reaction with the indicators within the agar such as dyes like neutral red, phenol red, methylene blue, etc. An example of a differential medium is ____ agar, which differentiates between bacteria on the basis of how they lyse blood cells. - correct answers Blood _____ hemolytic organisms completely lyse red blood cells (area is clear) - correct answers Beta _____ hemolytic organisms partially lyse red blood cells (media is a greenish color) - correct answers Alpha _____ hemolytic organisms do not lyse red blood cells (media remains unchanged) - correct answers Gamma EMB is a ______ AND _____ agar. - correct answers Selective & Differential
EMB is selective for gram ______ bacteria; the agar slightly inhibits the growth of gram _____. bacteria. - correct answers Negative, positive EMB also provides a color indicator that distinguishes between _________ fermenters and ______ non-fermenters. - correct answers lactose Lactose is sugar ______ can be used for water quality test; distinguishes between coliforms and fecal coliforms contamination in water samples. - correct answers EMB Mannitol Salt Agar is also _______ AND _______ for the isolation of staphylococcus aureus in clinical and non-clinical specimen. - correct answers Selective and differential It has beef extract, peptones, and a high concentration of sodium chloride (~7.5%) which prevents the growth of bacterial species other than staphylococcus. This is the time required for a bacterial cell (or a population of cells) to grow and divide. It is dependent on chemical and physical conditions. - correct answers Generation time Generation time is the time required for a population of cells to double in number. Most bacteria have a generation time of 1-3 hours, but under optimum conditions some have a generation time of 20 minutes or less. Logarithmic or exponential growth an increase a population's size dramatically. - correct answers Logarithmic A graph that plots the numbers of organisms in a growing population over time is known as - correct answers Growth Curve
Due to the transparency of the cytoplasm of microbes, ______ is necessary to create contrast. - correct answers Staining Coloring specimens with stains or dyes. An increase in contrast corresponds to an increase in ______. - correct answers resolution A ______ of microorganisms (thin film) is air dried to slide and then fixed to surface by heat or chemical fixation before staining can commence. - correct answers Smear Microbiological stains are salts composed of cations and anions, with one colored dye called - correct answers Chromophore This causes the specimen to adhere to the glass so that it does not easily wash off during staining. - correct answers Fixation (Heat-fix) What type of dyes stain alkaline structures? - correct answers Acidic dyes These are negatively charged (contain anionic chromophores) They do not stain bacterial cells (stains are repelled by negatively charged cytoplasm) They are usually used for negative staining protocols (stain outside of cells) What types of dyes stain acidic structures? - correct answers Basic Basic dyes are positively charged (contain cationic chromophores) Bacterial cells are slightly negatively charged so it creates an attraction between the positive dye and the negative cell
Methylene blue, crystal violet and basic fuchsin are what kind of dyes? - correct answers Basic Dyes Nigrosin, congo red and eosin are what type of dyes? - correct answers Acidic Is staining necessary for wet mounts? - correct answers NO. Staining is not necessary for wet mounts due to large size of microorganisms. Also not needed when observation of motility (Wet mounts and hanging drops) In this type of motion, all of the cells will be "jiggling"- moving a little bit but in no particular direction. - correct answers Brownian In this type of motility, many of the cells may not be moving, but the ones that are move a significant distance. - correct answers True motility If all of your bacteria are moving a lot in the same direction, make sure the water drop is not moving and simply sweeping the bacteria along with it. This is known as what type of motility - correct answers False motility This makes microbes adhere to the slide and permits them to accept the stain.
- correct answers Heat fixing ______ fixation is accomplished by using alcohols or aldehydes to denature or "fix" the specimens - correct answers Chemical Fixation These types of stains are composed of a single basic dye such as crystal violet, safranin, or methylene blue. - correct answers Simple Stains They are simple because they involve no more than soaking the smear in the dye for 30-60 seconds and then rinsing off the slide with water.
What is the mordant in the gram stain? - correct answers Iodine Mordants fix color into the cell or intensify color. All cells remain purple. what decolorizer is used in the gram stain - correct answers ethanol (acetone- alcohol) The smear is decolorized, gram-positive cells remain purple but gram- negative cells are now colorless. It creates large holes in the gram-negative cells outer LPS cell wall and washes out the iodine. The thick peptidoglycan layer in gram-positive cells retains the iodine. What is the counterstain in grams stain? - correct answers Safranin When viewed at oil immersion, gram-positive cells will appear purple and gram-negative cells will appear pink. This important differential staining technique differentiates between Mycobacterium and Nocardia. Pathogenic myobacterial species include the causative agents of tuberculosis (TB). and leprosy. - correct answers Acid- Fast staining Cells of these bacteria have large amounts of waxy lipid in their cell walls, so they do not readily stain with the water-soluble dyes used in gram staining. Acid-fast cells have a ____ cell wall. - correct answers Waxy Mycolic acid in the cell walls of acid-fast bacteria makes these organisms resistant to drying and disinfectants. This waxy cell wall also makes it difficult to stain these organisms with traditional stains that are water soluble. What is the primary stain in acid fast staining? - correct answers carbolfuchsin (red)
Heat is used to drive the stain through the waxy wall and into the cell, where it remains trapped. What decolorizer is used in the acid fast stain? - correct answers acid alcohol This removes color from both non-acid-fast cells and the background. Acid-fast cells retain their red color because the acid cannot penetrate the waxy wall. What is the counterstain in acid-fast? - correct answers methylene blue ______ the slide increases the fluidity of acid-fast cell walls and allows the carbol fuchsin to penetrate the cells. - correct answers Heating The Ziehl-Neelsen acid-fast staining procedure results in _____ acid-fast cells which can be differentiated from _____ non-acid-fast cells. - correct answers pink/red, blue This type of staining seek to identify various bacterial structures of importance (Ex: flagella, spores, capsules) - correct answers Endospore staining Some bacteria- Bacillus and clostridium- contain species that cause such diseases such as anthrax and produce endospores. These dormant, highly resistant cells from inside the cytoplasm of the bacteria and can survive environmental extremes such as desiccation, heat, and harmful chemicals. - correct answers Endospores They cannot be stained by normal staining procedures because their walls are practically impermeable at room temperature. What is the primary stain of endospore staining? - correct answers Malachite green
