Lab Quiz 3 Flashcards
purpose of oxidation requirement test
determine oxidation requirement of organism
OR: purpose of sodium throglycollate
combine with oxygen to reduce concentration
OR test: purpose of agar
Increase thickness of media to prevent diffusion of oxygen in media
OR test: purpose of resazurin
indicate presence of oxygen in tube. pink with oxygen, clear without oxygen present
define and describe obligate aerobe
- organism requires oxygen
- grown on top of media
define and describe microaerophile
- organism requires reduced concentration of oxygen
- grown above middle of agar
define and describe aerotolerant anaerobe
- grows equally well with or without oxygen
- grown all throughout media
define and describe facultative anaerobe
- can grow with or without oxygen but prefers aerobic conditions
- grow all throughout media but more at the top
obligate anaerobe
- can not grow in the presence of oxygen
- grows at the bottom of media
purpose of anaerobic bag test
determine if organism can grow in complete anaerobic conditions
indicator for bag test
methylene blue indicator strip. blue with oxygen and colorless without oxygen
reaction of anaerobic bag test
2H2 + O2 = 2H2O
Gelatin Hydrolysis test
- substrate: gelatin
- enzyme: gelatinase
- product: amino acids
+ gelatin hydrolysis test
- liquified agar deep after cooling
- gelatinase produced which broke down gelatin into amino acids and automatically liquified media
(-) gelatin hydrolysis test
- solid agar deep after cooling
- gelatinase not produced and no amino acids form. media remains solid
why is it necessary to refrigerate gelatin hydrolysis after incubation
to prevent gelatin from spontaneously liquifying after incubation
urease test
- substrate: H2O and Urea
- enzyme: Urease
- products: ammonia and CO2
(+) Urease test
- hot pink broth
- urease produced and breaks down urea into ammonia and CO2 which increases pH and phenol red changes from yellow to pink
(-) urease test
- yellow broth
- urease not produced. pH remains at 6.8 and phenol red does not change
urease indicator
- phenol red pH indicator
- yellow at 6.8, hot pink >8.4
SIM Test: 3 test done
- H2S
- Indole
- Motility
H2S test
- substrate: cysteine
- enzyme: cysteine desulfurase
- products: H2S and pyruvic acid
- H2S + ferrous sulfate = black ferric sulfide
indicator H2S test
ferrous sulfate
(+) H2S test
- black agar deep
- cysteine desulfurase produced which creates H2S that combines with ferrous sulfate in media to produce black ferric sulfide
(-) test
- yellow agar deep
- enzyme not produced, no H2S to combine with ferrous sulfate
Indole Test
- substrate: tryptophan
- enzyme: tryotophanase
- products: indole + Pyruvic acid
(+) indole test
- pink layer on top of agar deep
- organism produces tryptophanase and indole and purivic acid produced. indole detected using Kovacs reagent
(-) indole test
- yellow layer on top of agar deep
- enzyme not produced. tryptophan not hydrolysis to indole. indole reagent remains yellow
indole reagent
- kovacs reagent
Motility Test
- (+) test: growth diffusion away from stab line of inoculation
- (-) test: growth restricted to stab line of inoculation
Litmus Milk Test Substrates
lactose sugar and milk proteins
LM test: Acids
- pink opaque media
- organism uses lactose and acids are produced. pH decreases and litmus turns pink. Opaque since large milk proteins still present
LM test: Acids with reduction
- pink opaque media with white band at the bottom of tube
- organism uses lactose which produces acids. pH decreases and litmus turns pink. excess acid production reduced litmus and turns white. opaque media since milk proteins still present
LM test: Alkaline reaction
- purple opaque media
- organism uses milk proteins which are partially broken down. slight change in consistency and media
LM test: Peptonization
- deep purple/blue clear media
- organism uses milk proteins which are completely hydrolyzed to amino acids. ammonia produced from amino acids which increases pH. litmus turns deep purple/blue. clear media because proteins completely broken down.
Litmus Milk Test indicators
- litmus pH and oxidation-reduction indicator
(+) Motility Test
- growth dispersion from stab line, cloudy appearance
- organism is motile and was able to move away from line
(-) Motility Test
- broth restricted to stab line
- organism not motile, growth only seen along stab line
indicator used to determine results easier
- tetrazolium red indicator
Microbes in food: method used
- standard plate count
what is involved in a standard plate count and what does it determine
- serial dilutions of food/liquid sample in sterile water banks
- determine number of viable bacteria per mL of food sample
why is the standard plate count important for food, water, and milk industries
it is part of their quality control
calculation for organisms per ml or gram
number of colonies x final dilution factor
why is a plate with 25-250 colonies needed
greater than 250 is too many to count. less than 25 will cause unreliable and inaccurate results
Define Abstract
brief summary of experimentation. provides an over view of your work and the results obtained
components of abstract
- background info
- hypothesis/prediction
- testing method used
- results
advantage of abstract
not having to explain methods used in detail
Throat culture: media used
5% sheeps blood agar
5% sheeps blood agar
- NOT selective media
- differential media: 3 types of colonies based on hemolysis
TC: tests used
gram stain and catalase test
what test differentiates staphylococcus from streptococcus
catalase test
define hemolysis
destruction of RBCs
Aloha hemolysis
- partially lyse RBCs
- green zone surrounding colonies
Beta Hemolysis
- complete lysis of RBCs
- clear zone surrounding colony
Gamma Hemolysis
- do not produce hemolysins
- red agar surrounding colonies
