Lab One

Question 1

How is tryptic soy broth prepared?

Answer 1

70ml of distilled water is added to 4.2ml of TSB powder and mixed to dissolve and then another 70ml of distilled water is added

Question 2

What colour is tryptic soy broth?

Answer 2

light brown

Question 3

what is the feature of a none sterile liquid?

Answer 3

it is turbid (cloudy)

Question 4

what is a feature of a sterile liquid?

Answer 4

it is not turbid (clear)

Question 5

what was the only sterile broth in the sterillity lab experiment?

Answer 5

The bottle with the lid that was autoclaved

Question 6

what can cause a culture to be non sterile?

Answer 6

contamination from air, non-sterile container, non-sterile broth

Question 7

how is Tryptic Soy Agar prepared?

Answer 7

Agar is added to Tryptic Soy Broth, and then autoclaved to dissolve the agar and sterilize it. This is done under aseptic technique.

Question 8

what is the pH of tryptic soy agar?

Answer 8

7.3 +/- 0.2

Question 9

what is the formula of tryptic soy agar?

Answer 9

Tryptone (panreatic digest of casein) 17.0g

Enzytmatic digest of soybean meal 3.0g

Sodium chloride 5.0g

Di-potassium hydrogen phosphate 2.5g

Glucose (dextrose) 2.5g

Distilled water 1000ml

Question 10

what percentage of agar is added to the tryptic soy broth?

Answer 10

1.5%

Question 11

why is aseptic technique used?

Answer 11

to prevent the microbial contamination of laboratory workers, contamination from the environment they are working in and contamination of the species they are working on

Question 12

when is aseptic technique used?

Answer 12

whenever specimens are to be transferred between media

Question 13

what is subculturing?

Answer 13

use of aseptic technique procedures to maintain a pure culture when transferring microorganisms from media containing culture to fresh media not containing culture

Question 14

what is the first step in subculturing?

Answer 14

plate streaking is the first step in subculturing to ensure that the bacteria is pure, followed by microscopic examination

Question 15

what are the four subculturing procedures?

Answer 15

solid to solid- plate culture to plate
Solid to liquid- plate cultre to broth
Liquid to solid- broth culture to plate
Liquid to liquid- broth culture to broth

Question 16

what is the procedure of subculturing into a liquid media?

Answer 16

• agar plate, agar side up
• lid lightly loosened on the culture
• flame the loop tp sterilize and allow to cool
• remove the lid from the culture and flame the opening, do not put the lid down on the bench
• move the loop up and down on the side of the broth container
• flame the top of the bottle and replace the lid
• flame the loop

(loosen the lid slightly before incubation)

Question 17

what do you do to the lid of a bottle before incubation?

Answer 17

loosen it slightly to account for the build-up in pressure when inside the autoclave

Question 18

what is the procedure for subculturing onto a solid culture medium?

Answer 18

• place both plates agar side up
• flame the loop and allow to cool
• touch the loop to an isolated colony on the agar surface
• use the streak plate method

Question 19

what is the streak plate method?

Answer 19

• streaking a portion of the agar plate with an inoculum
• further portions of the plate are streaked to dilute the inoculum to form single colony-forming units (CFUs), which give rise to isolated colonies

Question 20

what are CFUs?

Answer 20

colony-forming units.

each colony-forming unit gives rise to an isolated colony

Question 21

when are the times to flame the loop in the streak plate method?

Answer 21

before picking up the inoculum
after streak 1
after streak 3

Question 22

what are proteus?

Answer 22

bacteria that are classified by being rapidly motile

Question 23

what is the structure of a proteus?

Answer 23

has a flagella that is visible when starined with a flagella stain

Question 24

how do protues move look on an agar plate?

Answer 24

when inoculated at the centre or agar, they swarm and form concentric rings

Question 25

why do proteus form the concentric ring pattern?

Answer 25

the concentric ring pattern occurs due to the cyclic repetition of alternating phases, swarming, active migration and consolidation

Question 26

what are the two cell types that a proteus can be in?

Answer 26

Swimming or swarmer cells

Question 27

what are the freatures of a swimmer proteus cell?

Answer 27

swimmer cells are shorter and oligoflagellated

Question 28

what are the features of swarmer proteus cells?

Answer 28

swarmer cells are elongated and hyperflagellated

Question 29

what effects the formation of the concentric ring pattern?

Answer 29

concnetric ring formation is sensitive to temperature, agar concentration, medium enruchment and bacterial density

Question 30

what does not effect the formation of concentric rings?

Answer 30

nutrient glucose depletion does not alter the formation of concentric rings

Question 31

what is the ideal temperature for commensal species isolated from the human body?

Answer 31

35 +/- 2 degrees

Question 32

what is the ideal temperature for many bacteria that are isolated form the environment?

Answer 32

usually 20 or 25+/- 2 degrees

Question 33

what effect does temperature have on the bacteria Serratia?

Answer 33

Higher temperature means that pigment formation is reduced

Question 34

how does a change in nutrient availability affect the bacteria Serratia?

Answer 34

if sucrose is available, extracellular polymeric substances are overproduced and the colonies are domed

Question 35

how can available nutrients affect bacteria?

Answer 35

it can alter the cell morphology

Question 36

what should be on the x axis of a graph?

Answer 36

The horizontal (x) axis should be a linear scale and contain the independent variable

Question 37

what should be on the y axis of a graph?

Answer 37

the vertical (y) axis is a logarithmic scale and contains the dependent variable

Question 38

what should a graph always have?

Answer 38

always have a title and all species names should be underlined
the units must also be specified

Question 39

can you tell if a broth culture is pure by looking at it?

Answer 39

No, you can’t tell if there is only one type of bacteria or if many present

Question 40

what are the reasons that single colonies may not be present on a streak plate?

Answer 40

the loop what too hot and killed the bacteria

there were too much bacteria on the plate (the loop wasn’t flamed between streaks)