Lecture 16

Question 1

carbon cycle

Answer 1

oxidized: CO and CO2
reduced: organic matter, methane
photosynthesis fixes CO2 into biomass (calvin cycle light reactions)
microbes fix 1/2 of world’s carbon
produces O2 and organic compounds
compounds oxidized back to CO2 by respiration

Question 2

anaerobic carbon cycling

Answer 2

methanogens
anaerobic archaea
energy by reducing CO2 and CH4
some living in symbiosis with termites and ruminants
methanotrophs: use methane as C source oxidizing it to CO2

Question 3

nitrogen cycle

Answer 3

atmospheric N2 –> Reduced Nigrogen NH4 –> oxidized nitrogen NO3 (nitrate)

Question 4

symbiosis

Answer 4

association of two or more organisms

Question 5

physical symboisis

Answer 5

ectosymbiont: organisms on another
endosymbiont: organism in another

Question 6

amensalism

Answer 6

adverse effect of one on another

• antibiotic production by bacteria and fungi kills other microbes
• petri dish with lawn of bacteria + disk of antibiotic in center (disk diffusion assay)

Question 7

parasitism

Answer 7

one benefits at expense of other (often partner coexist)

• viruses and host
• bacteriophage that’s lysogenic

Question 8

predation

Answer 8

predator kills prey

myxococcus prey on other bacteria

Question 9

cooperation

Answer 9

both benefit not obligatory
azotobacter fixes N2 into NH4
cellulomonas degrades cellulose

Question 10

commensalism

Answer 10

one benefits, other neutral

microbes on plants or animals

Question 11

mutualism

Answer 11

both benefit obligatory
vibrio and squid
tube worms and bacteria
photosynthetic algae and coral

Question 12

squid and vibrio relationship

Answer 12

mutalism
squid harvest vibrio during day
night squid feed at top of water; light from vibrio diffuses shadow and protects squid from below
vibrio fischeri have luciferase enzyme (glows when inside squid’s light organ)
- light production controlled by quorum sensing
- signaling molecules autoinducer acyl homoserine lactones
–reaches critical level, gene transcribed