Biochemical Tests Flashcards
What does the MacConkey Agar Test determine?
whether or not bacteria can ferment lactose to lactic acid
What does the MacConkey Agar Test promote the growth of?
gram negative bacteria
When does bacteria turn hot pink in the MacConkey Agar Test?
when bacteria can ferment lactose into lactic acid
What kind of colonies exhibit no colour change in the MacConkey Agar Test?
non-lactose fermenting colonies
What does the starch agar test determine?
some bacteria perform starch (amylose) hydrolysis via amylase
What does amylase break starch down into in the starch agar test?
glucose (monosaccharide) and disaccharides for catabolism
What happens if bacteria doesn’t have amylase in starch agar test?
starch isn’t broken down in plate and starch stays
What colour does iodide case remaining starch to turn in starch agar test?
dark purple
What does dark purple colour mean in starch agar test?
amylase negative
What does a clearing mean in starch agar test?
amylase positive
What does gram staining identify?
unknown species of bacteria
What is the motility test?
thinner agar used to allow mobile bacteria to move through agar
What does the motility test determine?
whether bacteria can move
What does a straight red line mean in the motility test?
negative test
bacteria weren’t able to move
What does a completely red agar mean in the motility test?
positive test
bacteria were able to move throughout agar
What percentage of sheep blood is in the hemolysis test?
5%
What does the presence of beta hemolysin mean in hemolysis test?
complete hemolysis with transparency
bright yellow
What does the presence of alpha hemolysin mean in hemolysis test?
partial hemolysis without transparency
dull yellow
What does the presence of gamma hemolysin mean in the hemolysis test?
no hemolysis
gray colour
What does the catalase test determine?
if organism is catalase positive it can break down hydrogen peroxide into water in oxygen
What does a positive catalase test result in?
bubbles
What does a negative catalase test result in?
no bubbles
