Microbiology Lab review

Lab 7

• Cardinal temperatures

Composed of a minimum a maximum and a optimum.

Example.

Psychrophile min -15C, optimum 0C, maximum 12.5C

Mesophile min 12.5C, optimum 37C,maximum 45C

Pathogens optiumum 37C Reason human body temperature.

Lab 7

• Oxygen requirements We tested these by using thylogylcolate tubes on the top

theses tubes were pink this was showing us the present of oxygen

Organism that grew throughout were the Aerotolerantanerobes

Organism that grew at the top the most and through out the broth were the Facultative anerobies.

Only at the top were the anerobesMake sure you know each type of organism, and the

enzymes they posess( catalase, and SOD) and why this is important.

Lab 7 oxygen requirements

Examples of tubes

Lab 8

• Broths

• Sucrose if the organism turns the broth yellow it has the ability to break down sucrose

• Dextrose if the organism is able to break down dextrose it can break down glucose.

• Durham tube traps CO2 if the organism is able to ferment either sugar it will make CO2 which the Durham tube will capture.

Examples

Lab 8

• TSI( Triple sugar iron)

• In this medium 3 sugars are in it including sucrose lactose and glucose. Glucose is in a lower amount so if glucose is utilize it will produce a lower amount of acid since this is a slant Oxygen will oxidizes the glucose so only the bottom will be yellow. If sucrose or lactose is utilize the entire tube will be yellow. If Iron is also incorporated so if the solution changes to black it means H2S are being produced from the break down of peptones. The H2S is reacting with FeSO4 producing the Black.

Example

Lab 9

• Sim ( sulfur indole motility)• This is a Semi-solid medium that has the indicator molecule

Fe(NH4)SO4, this molecule will react when H2S is produced from the break down of cystine . This tells us that the organism utilizes a enzyme called cystine desulfurase. When a organism possess a enzyme called tryptophanasethis breakes down tryptophan into a molecule called indoleand ammonium. We used the kovac’s reagent to test for this molecule. If it is red on top it means that it possesses tryptaphanase.

• Motility this is present when we see that the organism has moved throughout the tube.

Example

Lab 9

• Simmons citrate this is a synthetic medium. This medium has the PH indicator of bromothymoleblue. This will change from a green to a blue when the organism breaks down citrate into O2. The sodium in the medium will react with citrate producing sodium carbonate this is a basic product changing the medium blue. This tells us that the organism has the enzyme citrate permease. This is also a slant this is because it requires O2 to be present to oxidize citrate.

Example

Lab 9

• MRVP Methyl red Voges-Proskauer

• The Methyl red is a PH indicator that will change the medium only if the organism produces a lower PH than 4. Phenol red was 6.4-6.3. this is used because This organism is a mix acid fermented. VP utilizes barrits reagent to test for acetoin. This tells us if the organism has the pathway of the 2-3 butanediol.

• Positive for MR is yellow

• VP is red on the top Yellow on the bottom.

Example

Lab 10 Enzymes

• All the enzymes in this lab (except catalase) are exoenzymes.

• Cellulase This is a molecule that hydorlyzescellulose to glucose. This will have a zone around it. Tells us if the organism possess the enzyme cellulase. Uses Congo red to stain the agar and counter stain with NaCl.

• Starch medium this has this is the same in that there will be a zone that is positive. Tells us if the organism possess alpha- amylase. Will use grams iodine to stain the agar.

Examples

Lab 9

• Gelatinase

• This is a media that does not contain agar instead it has gelatin. Gelatin is boiled collagen and connective tissue. If a organism is able to break this down it tells us that this organism has this virulence factor . This tells us if the organism is able to break down our tissues and get deeper into our tissue. A positive test will be liquid after 20min in ice if solid the organism doesn’t posses gelatinase.

Example

Lab 9

• Catalase this is a to test if the organism is able to break down h202 into h20 and o2 the presence of bubbles indicates this.

Example

Lab 11

• Antibiotics • Know zone of inhibition• Can not compare the zone of inhibition to two

different antibiotics because of molecular weight.• Can only compare same antibiotic and different

bacteria to see how effective the antibiotic is.• Gram positive and gram negative antibiotics differ

in the cell wall since gram positives have a larger peptinoglycan they are more reliant on that wall then gram -.

Example

Lab 11

• Physical

• UV light unionizing

• Will make thymine dimer can kill the cell. Will mutate a lot of times.

Gamma radiation / x-rays ionizing rays

This will sheer DNA destroying it killing the cell. can mutated it.