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explain how capsule is visualized without the use of eyes that adhere to the capsule
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what 2 functions of the capsule or slime layer in bacterial cells
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Microbiology Lab
Lab Test 1 Part 2
| Question | Answer |
|---|---|
| explain how capsule is visualized without the use of eyes that adhere to the capsule | Capsule stains do not penetrate the capsule but rather form an opaque background surrounding the cell, highlighting the presence of the capsule. |
| what 2 functions of the capsule or slime layer in bacterial cells | The capsule can inhibit phagocytosis of pathogens, such as Streptococcus pneumoniae by white blood cells. The capsule also facilitates the attachment of bacterial cells to solid surfaces. |
| what biological molecules can make up the bacterial capsule or slime layer | Capsules are composed of polysaccharides or proteins. |
| function does the capsule have for streptococcus mutants | Streptococcus mutans forms a capsule that allows the bacterium to attach to the surface of a tooth. This results in the formation of a biofilm called plaque. |
| explain why bacterial capsule is considered a virulence factor | Because the capsule inhibits the immune system (see #1) and facilitates attachment to host cells/tissues, it has a greater capacity to cause disease. Any factor that increases the capacity to cause disease is called a virulence factor. |
| a student heat fixes his smear intended for a capsule staining. what might the student expect. | Heat causes the capsule to shrink because of the loss of water. Therefore, the student will probably not see a capsule in their stain. |
| look up the term virulence factor if you do not already know definition | are molecules produced by bacteria, viruses, fungi, and protozoa that add to their effectiveness and enable them to achieve the following: colonization of a niche in the host immunoevasion, evasion of the host's immune response. |
| functions of endospores in bacteria | Endospores are resting stages that allow bacteria to survive conditions unfavorable for growth. |
| external structure on the endospore acts as a protective barrier? what is its composition? | Endospores have a protective barrier on their exterior composed of protein. |
| compared to a vegetative cell how much less water is present in an endospore | Endospores contain 1030% of the water found in vegetative cells. |
| what is the mordant in the spore stain | Heat is the mordant in the endospore stain. It causes the endospore to expand allowing stain to penetrate the structure. |
| what is the stimulus for endospore production in bacteria | Nutrient depletion is usually the stimulus for endospore production. |
| what conditions are necessary to destroy endospores? what devices are these conditions achieved | Endospores must be exposed to 121°C, 15 psi of steam pressure for at least 1520 minutes. These conditions are achieved in an autoclave. |
| what color of endospores after gram staining? after spore staining? | After Gram staining, the endospore is colorless. After the endospore stain, it is green. |
| what is the secondary stain in the spore stain? | Safranin is the secondary stain in the endospore stain and is necessary to stain the vegetative cell. |
| color of the vegetative cell after spore stain? | The vegetative cell is red after the endospore stain. |
| of these three hrnerp of bacteria which does not produce endospores? clostridium, mycobacterium or bacillus? | Mycobacterium does not produce endospores. |
| are bacteria endospores reproductive structures and explain why or why not | Endospores are not reproductive structures, as there are no offspring created during the process. |
| give 3 examples of diseases caused by an endospore forming bacterium and the name of the specific bacterial agent involved. | Various answers are correct. Examples include botulism, tetanus, C. diff, food poisoning, etc. |
| m smegmatus and s epidermidis (kinyoun method) | Acid-fast cells (M. smegmatis) will be pink to red; non–acid-fast cells (S. epidermidis) will be blue. |
| what makes mycobacterium resistant to staining | Mycobacterium has a waxy cell wall that contains mycolic acid, a complex lipid that prevents stains from penetrating the cell. |
| what other bacterial genus is acid fast | Some Nocardia are acid-fast. |
| what is the primary stain in the kinyoun acid fast stain? and how does this differ from primary stain in the ziehl-neelsen method? | The primary stain in the Ziel-Neelsen method is carbolfuchsin, and basic fuchsin in the Kinyoun method. |
| what is the secondary stain in both acid fast stain methods | The secondary stain in the acid-fast stain is methylene blue. |
| in the ziehl-neelsen acid fast stain what is the mordant? | Heat is the mordant in the Ziel-Neelsen method. |
| if you conducted an acid fast stain on a sputum sample from a person with TB what would you expect to see on the slide | Mycobacterium tuberculosis cells would be pink rods, and human cells would be blue |
| what is the advantage of kinyoun staining procedure over the ziehl-neelsen method? | The Kinyoun method does not use heating in the procedure, and therefore noxious phenol fumes are not released |
| what are chromophores | Chromophores are color-bearing groups of stains. |
| what is the difference between basic and acidic dyes | Basic and acidic dyes differ in their charges, and therefore, they will be attracted to different parts of a slide when used to stain a specimen. |
| why do acidic dyes not stain bacterial cells | Acidic dyes are negatively charged, and therefore, they are repelled by negatively charged bacterial cells. Instead, they stain the background of a slide. |
| crystal violet is an example of what type of stain? | Crystal violet is a basic stain which has a positive charge. |
| what is meant by palisade arrangement of cells? | A palisade arrangement is a parallel arrangement of rod-shaped cells characteristic of t |
| if you were working with and unlabeled simple stained smear would you be able to identify the bacterial species by observing the slide under a microscope? why or why not? | Simple staining only indicates the shape, size, and arrangement of a bacterial species. Many different species have similar characteristics, and therefore, this would not be enough to determine the species |
| how would you differentiate between oral streptococci yeast and spirochaetes in your sample? | Streptococci are ovoid cells that occur in pairs or chains; yeasts are large ovoid cells that have characteristic buds |
| how would you differentiate between oral streptococci yeast and spirochaetes in your sample? | are much larger than bacteria; spirochetes are spiral-shaped cells that are very thin and usually not seen unless darkfield microscopy is used |
| Staphylococcus will be | spherical cells,. |
| whereas Bacillus | will be large rods |
| what type of chromophore is associated with negative stain | Negative stains have negatively charged chromophores and are repelled by negatively charged bacterial cells. |
| example of a negative stain | Nigrosin and India ink are examples of negative stains. |
| what step normally associated with staining bacterial cells is omitted when the dimensions of the cells are determined and why? | Heat fixation is normally omitted when determining dimensions of bacterial cells because heat will cause cells to shrink. |
| what external bacterial cell structures can be demonstrated by a negative cell stain? | Negative stains can demonstrate capsules. |
| S. aureus should be | purple (gram-positive) cocci in singles, pairs, short chains, and clusters. |
| P. aeruginosa should be | pink (gram-negative) bacilli in singles and pairs. |
| E. coli should be | short pink (gram-negative) bacilli in singles. |
| B. megaterium should be | very large purple (gram-positive) bacilli with or without clear spots representing spores (depends on age of the culture) in pairs or chains |
| M. catarrhalis should be | pink (gram-negative) cocci in pairs (diplococci). |
| why is the gram stain considered a differential stain | The Gram stain differentiates two types of bacteria based on the composition of their cell walls. It uses a primary stain, a mordant, a decolorizer, and a secondary stain to allow for the visualization of these structural differences. |
| how do gram positive and gram negative differ in cellular structure and how does this contribute to their differential staining properties part 1 | A gram-positive cell, which has a thick layer of peptidoglycan in its cell wall, retains the crystal violet-iodine complex better |
| how do gram positive and gram negative differ in cellular structure and how does this contribute to their differential staining properties part 2 | in the presence of the decolorizer as compared to gram-negative cell, which has a thin layer of peptidoglycan in its cell wall. |
| how does the age of culture affect the gram stain reaction what is an optimum culture age for a valid gram reaction? | Old cultures of gram-positive cells may not retain stain as well as younger cultures and could give false negative results, i.e., pink cells. Cultures that are 16–18 hours old are best. |
| which step in the gram stain procedure is mort prone to error and if done incorrectly how might this step affect the end result part 1 | The decolorizer step is very important because it is the step in which the cells become differentiated (gram-positive cells are purple and gram-negative cells are colorless). |
| which step in the gram stain procedure is mort prone to error and if done incorrectly how might this step affect the end result part 2 | If too much decolorizer is used, gram-positive cells will lose the primary stain and be counterstained pink. If too little decolorizer is used, gram-negative cells will not lose the primary stain and will remain purple after counterstaining |
| what is the function of a mordant? | mordant is used to form a complex with the primary stain, allowing it to become trapped or fixed into bacteria with certain structural properties. |
| which reagent serves this purpose in the gram stain procedure? | In the Gram stain, Gram’s iodine is used to form a complex with crystal violet, trapping it into gram-positive cells (and therefore, they are purple even after decolorization |
| its the reagents of the gram stain technique in order and their general role in the staining process | Crystal violet = primary stain (retained by gram-positive bacteria); Gram’s iodine = mordant; Alcohol/acetone = decolorizer; Safranin = counterstain (stains gram-negative bacteria). |
| what type of cell would you find lipoplusaccharide in its cell wall? gram negative or gram positive? | gram- negative |
Created by:
zachflemings