Exam 1 Objectives 2 Flashcards Preview

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Flashcards in Exam 1 Objectives 2 Deck (35)
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1
Q

identify genera that include acid fast species

A

mycobacterium, nocardia, cryptospordium, isospora

2
Q

what are the reagents in Zeil Neelsen procedures

A

carbolfuchsin stain=primary stain
acid alcohol=decolorizer
methylene bue=counter stain

3
Q

what are the reagents in Kinyoun procdures

A

carbolfuchsin
acid alcohol
brilliant green

4
Q

evaluate the differences between K and Zn methods of acid fast staining

A

Z uses steam to stain

K uses a more lipid soluble carbolfuchsin stain

5
Q

identify the composition of the decolorizer

A

composed of 95% ethanol and 3% HCl

6
Q

explain why acid fast bacteria are not decolorized

A

the mycolic acid in their cell walls resists the decolorization

7
Q

why are acid fast bacteria considered Gram nonreactive

A

their waxy cells repel typical aqueous stains

8
Q

explain the role of mycolic acids play in the acid fast staining reaction

A

give the cell a higher affinity for the stain and help it resist decolorization

9
Q

understand the reason for using a drop of serum to prepare the smear for the acid fast stain

A

to help the slippery acid fast cells adhere to the slide

10
Q

summarize the history and importance of the gram stain

A

developed in 1884 by Hans Gram; it is one of the most useful staining procedures because it classifies bacteria into two large groups(gram pos and gram neg)

11
Q

what is a primary stain in gram stain

A

crystal violet (stains the cell)

12
Q

what is the mordant in gram stain

A

iodine (forms a complex with the crystal violet to keep it in the cell)

13
Q

what is the decolorizer in gram stain

A

alcohol or acetone(allows complex to leave the gram negative cells)

14
Q

what is the counterstain in the gram stain

A

safranin (stains the gram negative cells pinkish)

15
Q

describe and compare the cell wall structure of gram positive and gram negative organisms

A

gram negative: higher lipid content, thinner peptidoglycan layer, outer membrane
gram positive: thicker peptidoglycan layer, teichoic acids, exoenzymes

16
Q

understand how the differing wall structure are affected by the decolorization step of the gram stain

A

the alcohol/acetone extracts the lipid making the gram negative wall more porous and incapable of retaining the crystal violet iodine complex. thereby decolorizing it

17
Q

identify the characteristics gram negative bacteria and those bacteria for whom the gram stain is not appropriate

A

gram nonreactive bacteria are bacteria without a cell wall such as mycoplasma species or with cell walls resistant to this staining procedure(like mycobacterium) cultures 24 hours old or less should be used

18
Q

identify the variables which can affect the results of a gram stain and understand how to limit the effects of these variables

A

the stain can be over decolorized by leaving the alcohol on too long(create reddish gram +) the stain can also be under decolorized creating purple gram - cells. inconsistency in preparation of the emulsification can also occur

19
Q

what is the difference between resident and transiet flora

A

resident remains part of the normal flora for life while transient remains only for hours, days or months(temporary)

20
Q

describe how soap and detergent differ

A

detergent is stronger than soap, detergents are synthetic. they both decrease surface tension so that microbes can be more easily removed

21
Q

explain how soap cleans

A

in greasy water, the hydrocarbon end of the soap molecule is soluble in oil and the carboxylate end is soluble in water, a chemical link forms between oil and water. then the oily ends of the molecules dissolve together. now the greasy oil is chemically combined with water and can be carried away

22
Q

understand why soap is not an effective cleansing agent when used with hard water

A

hard water contains mineral salts, when soap is used with this magnesium and calcium salts react with soapy oil droplets forming a lighter than water precipitate. this scum with its load of grease and bacteria adheres to whatever is being washed

23
Q

evaluate the effectiveness of an antiseptic detergent in removing surface organisms

A

antiseptic detergents work better than regular soap

24
Q

describe the importance of preparing control plates when performing experiments

A

so that you can distinguish between bacteria that possible came from the substance you were using and the resident/transient bacteria on the hand

25
Q

the single line with zigzag was used to separate the CFUs for this experiment to

A

spread it around and to see the possible different organisms (distribution)

26
Q

four characteristics of microbial morphology

A

color, size, shape, and texture

27
Q

positively charged ion

A

cation

28
Q

negatively charged ion

A

anion

29
Q

substance that can be readily converted into a dye or other colored compound (colored molecule)

A

chromogen

30
Q

part of a molecule responsible for its color

A

chromophore

31
Q

the charged portion of a chromgen and allows it to act as a dye through ionic or covalent bonds between the chromogen and the cell

A

auxochrome

32
Q

differentiate between basic and acidic dyes and how they work

A

acidic- carries a negative charge because it is missing a hydrogen
basic- carries a positive charge and forms an ionic bond with the negatively charged bacterial cell

33
Q

understand why when using solid media the inoculum is serially diluted on the slide

A

the concentration of the bacteria is too high, serial dilution takes place to help isolate the bacterium on the slide better

34
Q

know the purpose of air drying

A

excess water left on the slide will boil during the fixing stage and cause most microbes present to rupture and become airborne, also stick to the slide

35
Q

know the purpose and effects of heat fixing a slide

A

basic stains are heat fixed to kill bacteria, make them adhere to the slide, and coagulate cytoplasmic proteins to make them more visible under the microscope