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)