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micro 224 lab midterm 2 ex. 7-15

Terms in this set (96)

Purpose of fermentation test
used to detect an organisms ability to ferment carbohydrates
which type of bacteria are fermentation tests most helpful to distinguish between
Gram negative bacilli particularly those that are members of the family enterobacteriaceae
which media are used during fermentation tests
phenol red broth and bromocrescol purple broth
both media allow for testing of acid and gas production through the fermentation of various carbohydrates
3 ways microorganims break down carbohydrates
- fermentation
- aerobic respiration
- anaerobic respiration
how does fermentation differ from respiration
fermentation involves glycolysis
while respiration involves glycolysis + kreb cycle + ETC
how is ATP created during glycolysis
through substrate level phosphorylation
how is ATP created during respiration
oxidative phosphorylation
electron receptor in glycolysis vs respiration
glycolysis- endogenous molecule
respiration- exogenous
why can microorganisms survive using just glycolysis
because they are so small with low energy requirements they can survive off just glycolysis
how are fermentation patterns useful when identifying species
because different bacteria utilize different carbon sources
- they have certain enzymes which allow them to break down different molecules
What is phenol red?
broth we used in this lab, acts as a pH indicator is red at neutral pH, yellow below 6.4 and red above 8
what happens when fermentation occurs in phenol red broth
acid is produced turning the phenol red yellow
what is a durham tube
placed inverted in the test tube to trap any gas that is produced (another by product of fermentation)
what were the five sources of carbohydrates we tested
glucose
lactose
maltose
mannitol
sucrose
some bacteria ferment glucose but not sucrose even though sucrose is a disaccharide composed of glucose and fructose. explain
Most bacteria need exposed glucose to ferment glucose. The glucose that is in sucrose is bound to fructose which makes it big, reduces the available binding areas, changes the charges characteristics. (basically it's not the same molecule as independent glucose). Sucrose requires a much BIGGER enzyme to break it down than glucose does. Enterobacter ferments sucrose, E. coli cannot
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