Lab 2

Question 1

Cellular Morphology

Answer 1

Size (short); shape (singular), arrangement (rods)

Question 2

Successful cultures depend on

Answer 2

Medium ingredients and chosen conditions

Question 3

Media provide both ___________ for growth of organisms

Answer 3

Macro and micronutrients

Question 4

Macronutrients

Answer 4

carbon and nitrogen, phosphorous, sulfur, potassium, magnesium, sodium and iron

Question 5

Macronutrients are used and measured in

Answer 5

decreasing quantity and added to media in milligrams and grams

Question 6

Micronutrients are

Answer 6

cobalt, zinc, copper, manganese

Question 7

Micronutrients are used in (measurement)

Answer 7

in micrograms and in very small quantities

Question 8

Media can be classified into (5)

Answer 8

1. Chemically Defined/synthetic medium
2. Complex/Undefined medium
3. Enrichment medium
4. Differential medium
5. Selective medium

Question 9

Chemically defined/synthetic medium

Answer 9

• ingredients are chemically defined and quantifiable
• they cannot contain any undefined complex soluble extracts from animal (beef extract) or plants (malt extract-sugar) or fungi (yeast) or special supplements like serum or blood

Question 10

Complex/Undefined medium

Answer 10

• NOT all ingredients are chemically defined and quantifiable
• Can contain animal and plant extracts and other sources like serum, blood, sea water or soil.
• These media are rich in nutrients and are ideal for culturing most heterotrophic microorganisms.

Question 11

Enrichment medium

Answer 11

• Contains an ingredient to encourage growth of a particular fastidious (want a specific thing to grow) organism
• for example, 5% sheep blood is added to Tryptic Salt agar to prepare Blood Agar
• This medium is also differential

Question 12

Differential medium

Answer 12

• It allows for identification of a particular organism by its appearance or by the way in which it changes the medium during growth
• for example how bacteria interact with added blood
• Streptococcus pyogenes produces a clear zone (beta haemolysis)-rupture of red blood cells
• S. pneumonia produces a greenish zone (alpha haemolysis)
• S. epidermidis produces NO heamolysis (gamma heamolysis)

Question 13

Mannitol Salt agar and MacConkey agar

Answer 13

differential medium AND selective medium in function

Question 14

Mannitol Salt agar

Answer 14

• fermentation of carbohydrate mannitol leads to acid production, which lowers the pH of the medium and it causes the ph indication to change from red to yellow
• it forms a yellow zone around its colonies
• contains 7.5% NACL that inhibits the growth of gram negative and positive bacteria except staphylococci

Question 15

MacConkey agar

Answer 15

• fermentation of lactose yields brick red colonies

- inhibits the growth of gram positive bacteria

Question 16

Selective medium

Answer 16

• contains an ingredient(s) inhibitory to all but one particular microorganism.
• it may even lack an ingredient necessary for most microorganisms to grow like N. (Nitrogen free Mannitol agar)

Question 17

Growth medium

Answer 17

Tryptic soy agar

Question 18

Tryptic soy agar

Answer 18

-purpose is to grow a wide variety of aerobic and facultative anaerobic heterotrophic bacteria
-Complex medium containing a.a and peptones carbon and nitrogen sources and 0.5% NaCl to maintain the osmotic pressure.
-a.a and petones are derived from the enzymatic digestion of casein and soy meal.
-also it contains, 1.5% of agar as a solidifying agent.
without the agar it is tryptic soy broth NOT an agar

Question 19

Agar

Answer 19

• complex polysaccharide extract from red-purple algae
• used a solidifying, gelling agent in media at a 1.5% concentration.
• semi solid media for bacterial motility
• after preparing it must be sterilized-this is done by autoclaving

Question 20

Skin

Answer 20

• primary function is to not lose moisture
• physical barrier to the entry of pathogens and toxic substances
• contains immune defenses-lysozomes
• 200 genera of bacteria
• Gram positive are predominant on the skin (thick peptidoglycan)

Question 21

Skin-experiement

Answer 21

• use of Mannitol Salt Agar (MSA)
• a selective differential medium
• and the streak technique used to isolate staphylcocci and other gram positive bacteria from skin
• 7.5% of NACL in MSA selects specifically for gram positive and staphylococcus bc of their greater tolerance to the increased osmotic pressure by the salt
• Target the isolation of STAPHYLOCOCCUS AUREUS.
• it is important bc it can ferment the sugar alcohol mannitol and produce colonies with yellow zones on the MSA.

Question 22

SALIVA experiment

Answer 22

• streptococcus mutans-initiation of dental caries
• use Mitis Salivarius Agar
• selective differential medium
• PURPOSE- to isolate S. mitis and S. salivarius
• Selective ingredient are Potassium Tellurite to inhibit the growth of most bacteria except oral streptococci and crystal violet to inhibit the growth of gram positive bacteria except oral cocci.
• The differential ingredient is sucrose
• S. salivarius produces a rough frosted glass or gum drop colony
• S. mitis doesn’t ferment sucrose and it produces small colonies

Question 23

Fresh water experiement

Answer 23

• purpose to isolate gram negative bacteria and E. coli
• using the MacConkey (cons and keys) agar (MAC) as a selective and differential medium
• differential medium-presence of bile salts and crystal violet in mac makes it selective for gram negative bacteria
• E.coli is inherently more resistant to salts that other gram negative bacteria
• E. coli can be differentiated from other colonies by their ability to ferment the sugar lactose.
• Fermentation of lactose yields acids, acids lower the PH of the medium, therefore the ph indicator changes colour from light pink to brick red.
• As ph lowers further a pink halo of precipitated bile salts will form in the medium around e. coli
• Indication of brick red colonies with pink halos, indicated successful isolation of E. coli

Question 24

Terms to describe typical colony morphology (6)

Answer 24

1. form-circular
2. colony size-small, medium
3. colour-pigment as pink, opacity of a colony as transparent
4. texture-smooth, dry, glistening
5. elevation-raised, flat, convex, concave
6. Margin-entire, irregular

Question 25

Halophiles

Answer 25

-organisms that require high salt concentrations for growth (3-15% nacl)

Question 26

extreme halophiles

Answer 26

need 20-30% of nacl - found in solar salterns, salt mines and ancient salt lakes - pinkish red colours bc of presence of carotenoids

Question 27

Halobacterium can grow.....

Answer 27

1. chemoheterotrophically in the dark 2. phototrophically in the light - harvest light energy with the membrane protein bacteriorhodpsin

Question 28

Bacteriorhodpsin

Answer 28

-protein functions like a proton pump to generate a proton gradient and then it is used to form ATP

Question 29

Halobacterium diet??

Answer 29

-need a source of carbon since they are heterotrophs

Question 30

Halobacterium salinarum (description)

Answer 30

-motile rod -grows aerobically at an optimal temp it can form intracellular gas vesicles

Question 31

Intracellular gas vescles

Answer 31

- hollow structures surrounding a gas filled space within a cell - provides a buoyancy so the cells can remain afloat in the water to optimally absorb light or obtain oxygen for growth

Question 32

Halobacterium is attacked by

Answer 32

-brine shrimp

Question 33

Halobacterium description of the experiement

Answer 33

- 25% nacl - use the microscope to examine the enrichments for the presence of motile rods and intracellular gas vesicles - then we will isolate the colonies on the halobacterium agar medium for isolated colonies and look for the formation of pink to red colonies

Question 34

washing hands 2 techniq

Answer 34

1. soap and water (soap contains antimicrobial 0.3 % chloroxylenol.) 2. Hand gel has 60% ethyl alcohol

Question 35

efficacy testing of hand washing and alcohol based gel

Answer 35

-on tryptic soy gel (left side is the control and the right side is the treatment side) -