Exam 1 Objectives 2

Question 1

identify genera that include acid fast species

Answer 1

mycobacterium, nocardia, cryptospordium, isospora

Question 2

what are the reagents in Zeil Neelsen procedures

Answer 2

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

Question 3

what are the reagents in Kinyoun procdures

Answer 3

carbolfuchsin
acid alcohol
brilliant green

Question 4

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

Answer 4

Z uses steam to stain

K uses a more lipid soluble carbolfuchsin stain

Question 5

identify the composition of the decolorizer

Answer 5

composed of 95% ethanol and 3% HCl

Question 6

explain why acid fast bacteria are not decolorized

Answer 6

the mycolic acid in their cell walls resists the decolorization

Question 7

why are acid fast bacteria considered Gram nonreactive

Answer 7

their waxy cells repel typical aqueous stains

Question 8

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

Answer 8

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

Question 9

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

Answer 9

to help the slippery acid fast cells adhere to the slide

Question 10

summarize the history and importance of the gram stain

Answer 10

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)

Question 11

what is a primary stain in gram stain

Answer 11

crystal violet (stains the cell)

Question 12

what is the mordant in gram stain

Answer 12

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

Question 13

what is the decolorizer in gram stain

Answer 13

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

Question 14

what is the counterstain in the gram stain

Answer 14

safranin (stains the gram negative cells pinkish)

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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

Question 19

what is the difference between resident and transiet flora

Answer 19

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

Question 20

describe how soap and detergent differ

Answer 20

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

Question 21

explain how soap cleans

Answer 21

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

Question 22

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

Answer 22

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

Question 23

evaluate the effectiveness of an antiseptic detergent in removing surface organisms

Answer 23

antiseptic detergents work better than regular soap

Question 24

describe the importance of preparing control plates when performing experiments

Answer 24

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

Question 25

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

Answer 25

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

Question 26

four characteristics of microbial morphology

Answer 26

color, size, shape, and texture

Question 27

positively charged ion

Answer 27

cation

Question 28

negatively charged ion

Answer 28

anion

Question 29

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

Answer 29

chromogen

Question 30

part of a molecule responsible for its color

Answer 30

chromophore

Question 31

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

Answer 31

auxochrome

Question 32

differentiate between basic and acidic dyes and how they work

Answer 32

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

Question 33

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

Answer 33

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

Question 34

know the purpose of air drying

Answer 34

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

Question 35

know the purpose and effects of heat fixing a slide

Answer 35

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