Lab Exam 2

Question 1

Starch hydrolysis

Answer 1

Does microbe have exoenxyme to hydrolyze starch. (Amylase). Negative-blue/brown colour, positive-colorless. Reagent-Grams iodine colour change in presence of starch.

Question 2

Catalase Test

Answer 2

IDs hydrogen peroxide as a product of aerobic respiration. If there are bubbles this is oxygen gas produced in reaction with H2O2.

Question 3

Carbohydrate fermentation.

Answer 3

Phenol red is pH indicator. Red if neutral/basic and yellow if acidic. Gas bubbles caught in Durham tube. Fermentation products-gas,acid, alcohol. Lactose, sucrose and maltose.

Question 4

Reagent

Answer 4

Chemicals that produce a visible evidence that indicates a biochemical reaction has occurred

Question 5

Citrate utilization

Answer 5

Medium-Simmons citrate (only carbon source). Bromthymol blue is pH ID, green neutral, blue +7.5. Citrate permeases transport citrate into cell>pyruvic acid and CO2>CO2 diffuses out of cell reacts w/ Na>NaCO3 which makes medium more basic. Positive is blue vv green.

Question 6

Gelatin Hydrolysis

Answer 6

Exoenzyme, medium is nutrient gelatin. If gelatin digested medium liquefies. Liquid=positive. Issues low temp and long incubation. Gelatinase hydrolyzes gelatin protein into smaller peptides and AAs.

Question 7

SIM

Answer 7

Sulfur Indole Motility. Tryptophan>indole produced through tryptophanase hydrolyze into pyruvate, ammonia (deamination) and indole. Add Kovacs reagent has compound which reacts with indole > red. Sodium thiosulfate. Cysteine desulfurase can can catalyze putrefaction of AA cysteine to pyruvic acid which produces H2S gas. Combines with iron in medium to create ferric sulfide a black precipitate. Motility- radiating growth appears fuzzy allowed by reduced agar content.

Question 8

Urease

Answer 8

Products: CO2 and ammonia. Urea broth with phenol red. If positive then colour orange>pink. Rise in alkalinity of medium from ammonia.

Question 9

Negative citrate test

Answer 9

Transfer nutrient agar, lack citrate permease, heat killed bacteria. If you transfer nutrient agar the bacteria can grow even if it doesn’t have citrate permeases.

Question 10

Sim tests for

Answer 10

H2S (cysteine digestion). Indole (tryptophan digestion). Motility.

Question 11

Test that require pH change

Answer 11

Citrate and urease

Question 12

Digest AAs tested by

Answer 12

Cysteine>H2S, tryptophan >Indole.

Question 13

Broad vs narrow spectrum

Answer 13

Broad many microbes and taxonomic groups, narrow 1tax group few

Question 14

Disk diffusion test

Answer 14

Used to determine the sensitivity of microbe antimicrobial agent, agar covered with microbe filter paper with agents placed on look for area of inhibition. 1. Measure diameter, 2. Compare with chart, 3. If gram +- both susceptible=broad spectrum.

Question 15

Bacterial transformation

Answer 15

Insertion of new DNA into bacteria. Change in genes, insert gene new traits

Question 16

pGLO plasmid

Answer 16

GFP, bla (ampicillin resistance), araC (arabinose operon).

Question 17

Role heat shock and CaCl2

Answer 17

Heat allows genes to enter cell. CaCl ionizes Ca2+ ion neutralizes charge on the phosphate backbone and phosoLs of PM allowing plasmid to enter.

Question 18

GFP and arabinose relationship

Answer 18

Medium has arabinose sugar allows for gene expression. In plasmid some of arabinose genes replaced with GFP. Arabinose in medium+successful transformation> GFP activated and GF proteins expressed.

Question 19

Serology

Answer 19

Study antiG and antiB interactions.

Question 20

Immunofluorescene test.

Answer 20

Coat wells with antiG/org. Add patient serum. If antiB specific to antiG in serum binds to antiG. Wash to remove unbound antiBs. Fluorescent dye that is specific to the immune complex is added. Look for fluorescence under microscope. E.g. If HIV+ then HIV specific antiB binds to HIV antiG in plate and fluorescent.

Question 21

ELISA

Answer 21

Enzyme-linked Immunoabsorbent Assay. Neither ELIsA of western blot are antiG linked.

Question 22

Titer

Answer 22

Most diluted concent of serum antiBs that produce a detectable immune response. Indicator of relative concent of antiG specific antiB in patients serum.

Question 23

Possible ELIsa results

Answer 23

1st exposure: 1 zero ABs, 7 low level, 14 big number, 21 low again. 2nd exposure: 1 some circulating ABs, 7 big amount, 14 big amount, 21 big amount. Vaccine no exposure- low level AB constant circulation. 0s every day no exposure no current case.

Question 24

Differential medium

Answer 24

Allows microbiologists to distinguish between groups of microbes.

Question 25

Selective medium

Answer 25

Ingredient encourage growth of some microbes and discourage others.

Question 26

Enriched medium

Answer 26

Added ingredients provide growth factors for fastidious orgs.

Question 27

Blood agar

Answer 27

Enriched bc added sheeps blood as growth factor. Differential because orgs digest blood difly no digest-gamma, partial-alpha, full-beta.

Question 28

Resolution

Answer 28

Clarity of microscope. Smallest distance between 2 nearby objs can B distinguished

Question 29

Smear prep

Answer 29

Dye disassociates in solution cytoP negative charge attracts positive dye mc. Wash and dye mc remains.

Question 30

Gram stain

Answer 30

1cyrstal violet-2x purple, 2-Grams iodine 2x purple, 3- alcohol +purple -colorless, 4- safranin +purple -pink. +thicker peptidG walls entrap dye -alcohol dissolves PM.

Question 31

Acid fast

Answer 31

Mycobacterium tuberculosis.