Lab Quiz 10: Microbial Symbioses, Exoenzymes, and Gram Negative/Positive Biochemical Tests (Bio 286 - Microbiology) Flashcards
competition
a contest between organisms for territory, a niche, or resources; neither organism fully thrives as both are somewhat harmed; example: soil bacteria for carbon sources
cooperation
process of groups of microbes working or acting together for their common/mutual benefit; both organisms can benefit from this interaction; example: quorum sensing
predation
interaction where a predator (an organism that is hunting) feeds on its prey (the organism that is attacked); predator benefits but the prey does not; example: Paramecium consuming bacteria
mutualism
relationship between two organisms in which individual benefits from the activity of the other; example: lichen, ruminants, and alfalfa
commensalism
class of relationships between two organisms where one organism benefits without affecting the other; example: many members of the human microbiota that benefit from humans but the humans do not benefit
amensalism
an interaction where an organism inflicts harm to another organism without any costs or benefits received by the actor; example: antibiotic production by a fungus
parasitism
interaction where one species (the parasite) benefits at the expense of the other (the host); example: bacteriophage T4 (and all viruses in general)
staphylococcus aureus and clostridium sporogenes have a
commensalistic relationship (commensalism)
does staphylococcus aureus or clostridium sporogenes benefit from their commensalism?
clostridium sporogenes
MacConkey Agar
if the microbes ferment lactose then the acids they produce turn the indicator dyes red… a positive result is red and a negative result is no change
indole
if microbes breakdown amino acid tryptophan to indole, the indole reacts with Kovac’s reagent to turn bright red… a positive result is red and a negative result is yellow
Triple Sugar Iron Agar (slant)
if ammonia is produced then the pH of the media becomes neutral – red and if lactose/sucrose is fermented then the tube will remain yellow… a positive result is yellow (A) and a negative result is red (K)
triple sugar iron agar (butt)
the butt of the TSI is always yellow – a positive result is yellow (A)
triple sugar iron agar (gas)
gases produced during fermentation will appear as bubbles or cracks… a positive result is cracking and a negative result is no change/no cracking
triple sugar iron agar (H2S)
hydrogen sulfide produced from breakdown of amino acid cysteine reacts with the iron to form ferric sulfide which is black… a positive result is black and a negative result is no change
MRVP (methyl red)
turns red in the presence of organic acids… a positive result is red and a negative result is yellow
MRVP (voges proskauer)
detects acetoin to turn red in its presence… a positive result is red and a negative result is coppery brown/no change
citrate
at acidic pH (citrate present) the media is green and if the citrate is metabolized the pH will turn blue… a positive result is blue and a negative result is green
urea
under alkaline conditions the indicator will turn pink… a positive result is bright pink and a negative result is yellow/no change
indole negative result
yellow
indole positive result
RED
methyl red negative result
yellow
methyl red positive result
RED
voges proskauer negative result
no change (yellow brown)
voges proskauer positive result
RED
citrate negative result
green
citrate positive result
BLUE
MacConkey Agar (MAC) negative result
no change (not red– brown or tan)
MacConkey Agar (MAC) positive result
RED
urea negative result
no change (yellow)
urea positive result
PINK
TSI (slant) negative result
K - red
TSI (slant) positive result
A- YELLOW
TSI (Butt) negative result
K - red
TSI (Butt) positive result
A - YELLOW
TSI (gas) negative result
no change/no cracks
TSI (gas) positive result
CRACKS
TSI (H2S) negative result
no change/yellow
TSI (H2S) positive result
BLACK
mannitol salt agar
selective and differential media; contains 6.5% NaCl, phenol red dye, and mannitol…. microbes that are able to grow may ferment mannitol or not (if they do, the acids they produce turn the indicator dyes in the media yellow)
mannitol salt agar (MSA) growth positive result
GROWTH
mannitol salt agar (MSA) growth negative result
no growth
mannitol salt agar (MSA) fermentation negative result
red
mannitol salt agar (MSA) fermentation positive result
YELLOW
catalase
enzyme that decomposes hydrogen peroxide to water and oxygen gas– when H2O2 is placed on the microbes, the production of bubbles indicates a positive reaction
catalase (H2O2) negative result
no bubbles
catalase (H2O2) positive result
BUBBLES
EF broth
media containing a fermentable sugar (glucose) and an acid indicator (bromcresol purple)– glucose fermentation results in acid end products, which cause the media to turn yellow… the media also contains a metabolic poison sodium azide, allowing only azide-resistant microbes to grow
EF broth negative result
purple
EF broth positive result
YELLOW
NaCl broth
contains 6.5% NaCl, allowing only halotolerant microbes to grow and turn the media cloudy
NaCl broth negative result
clear
NaCl broth positive result
CLOUDY
bile esculin slant
media used to detect the metabolism of a compound called esculin– if it is converted to esculetin, it will react with iron in the media and turn completely black… bile acids in this media inhibit the growth of most gram positive organisms
bile esculin (BE) slant negative result
tan
bile esculin (BE) slant positive result
BLACK
DNase
breaks down DNA to nucleotides by adding HCl to the DNA plate after microbes have been cultured– the low pH causes DNA to precipitate within the media, turning the late cloudy. any areas where DNA has hydrolyzed will not precipitate, leaving clear areas around growth of positive cultures
DNase (HCl) negative result
no clearing
DNase (HCl) positive result
CLEARING
sheep blood agar
some bacteria break down blood cells using toxins called hemolysins… resulting in three patterns of hemolysis clearings- alpha, beta, and gamma… additionally, bacitracin and optochin are antibiotics used to determine susceptibility
alpha hemolysis
partial breakdown of red blood cells– resulting in smoky green color (no longer red but no clearing)
beta hemolysis
complete breakdown of red blood cells, resulting in complete clearing– can read text through the plates
gamma hemolysis
no clearing, the plates have growth on them but are just as red
hemolysis results
alpha (A), beta (B), or gamma (G)
bacitracin
an inhibitor of peptidoglycan biosynthesis that group A streptococci are particularly susceptible to
bacitracin negative result
no zone (R)
bacitracin positive result
ZONE (S)
optochin
a copper containing compound that pneumococci are particularly susceptible to
optochin negative result
no zone (R)
optochin positive result
ZONE (S)
lysozyme
protein found in tears/saliva/other secretions and egg whites… a peptidoglycan hydrolase and is an important component of our innate immune defenses
Alexander Fleming
described lysozymes
