Lab 2 Flashcards
Cellular Morphology
Size (short); shape (singular), arrangement (rods)
Successful cultures depend on
Medium ingredients and chosen conditions
Media provide both ___________ for growth of organisms
Macro and micronutrients
Macronutrients
carbon and nitrogen, phosphorous, sulfur, potassium, magnesium, sodium and iron
Macronutrients are used and measured in
decreasing quantity and added to media in milligrams and grams
Micronutrients are
cobalt, zinc, copper, manganese
Micronutrients are used in (measurement)
in micrograms and in very small quantities
Media can be classified into (5)
- Chemically Defined/synthetic medium
- Complex/Undefined medium
- Enrichment medium
- Differential medium
- Selective medium
Chemically defined/synthetic medium
- 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
Complex/Undefined medium
- 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.
Enrichment medium
- 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
Differential medium
- 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)
Mannitol Salt agar and MacConkey agar
differential medium AND selective medium in function
Mannitol Salt agar
- 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
MacConkey agar
- fermentation of lactose yields brick red colonies
- inhibits the growth of gram positive bacteria
Selective medium
- 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)
Growth medium
Tryptic soy agar
Tryptic soy agar
-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
Agar
- 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
Skin
- 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)
Skin-experiement
- 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.
SALIVA experiment
- 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
Fresh water experiement
- 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
Terms to describe typical colony morphology (6)
- form-circular
- colony size-small, medium
- colour-pigment as pink, opacity of a colony as transparent
- texture-smooth, dry, glistening
- elevation-raised, flat, convex, concave
- Margin-entire, irregular
Halophiles
-organisms that require high salt concentrations for growth (3-15% nacl)
extreme halophiles
need 20-30% of nacl
- found in solar salterns, salt mines and ancient salt lakes
- pinkish red colours bc of presence of carotenoids
Halobacterium can grow…..
- chemoheterotrophically in the dark
- phototrophically in the light
- harvest light energy with the membrane protein bacteriorhodpsin
Bacteriorhodpsin
-protein functions like a proton pump to generate a proton gradient and then it is used to form ATP
Halobacterium diet??
-need a source of carbon since they are heterotrophs
Halobacterium salinarum (description)
-motile rod
-grows aerobically at an optimal temp
it can form intracellular gas vesicles
Intracellular gas vescles
- 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
Halobacterium is attacked by
-brine shrimp
Halobacterium description of the experiement
- 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
washing hands 2 techniq
- soap and water (soap contains antimicrobial 0.3 % chloroxylenol.)
- Hand gel has 60% ethyl alcohol
efficacy testing of hand washing and alcohol based gel
