Lecture 10

Question 1

Thiomargarita energy generation (nitrate storing sulfur bacteria)

oxidation of what?
reduction of what?

Answer 1

oxidation of H2S
reduction of NO3- (possible O2, SO4-)

in the upper zone:
- cells accumulate up to 0.8 M NO3- in the vacuoles
- may also reduce O2 as TEA (aerobic respiration)
- can be a facultative anaerobe but prefers a low O2
-the cells carry their own supply of NO3- to the lower zone
- allows the cells to oxidize H2S in the lower zone.

Question 2

thiomargarita energy generation

Answer 2

• large size needed for NO3- storage,, because cells are non-notile
• strategy possible because of turbulence
• carbon source unknown
• many of the metabolic mysteries were solved via single-cell genomic sequencing

Question 3

what is thiomargarita ?

Answer 3

Nitrogen-storing Sulfur Bacteria

Question 4

describe beggiatoa

• electron donor and acceptor?

Answer 4

• similar H2S oxidizing lifestyle
• inhabit the oxygen-sulfide interface (gradient organisms)
• follow the O2-H2O interdace up into the overlying water
• prefer O2 as terminal electron acceptor
• stores NO3- on vacuoles for survival under anoxic conditions
• close relatives of Thioploca.

Question 5

name a few nitrate-storing sulfur bacteria

Answer 5

beggiatoa
thiomargarita
thioploca

Question 6

describe Thioploca

Answer 6

• thioploca inhabits a niche similar to that of thiomargarita, and has a similar metabolic strategy, but is MOTILE and SMALLER
• Takes up and stores NO3- in the upper zone
• generates energy via oxidize of S0 to SO4 2- in the upper zone and H2S to S0/SO42- in the lower zone

terminal electron acceptor: NO3- is reduced to NH4+
C source: CO2 or acetate (facultative chemolithoautotrophs)