Ch 14.4-14.6 (Book) Flashcards
obligate aerobe
bacteria that only grow using O2 as the TEA
anaerobic respiration
using TEA other than O2
ex. nitrogen, sulfur, metal, chlorinated organics
E. coli different terminal oxidoreductases
allow reduction of alternative TEA
trimethylamine
causes fishy odor
reduced by bacteria
are there different initial substrate oxidoreductases?
yes, receive e- from different organic donors
do bacteria use the strongest e- donor and strongest acceptors available?
yes
which type of bacteria often utilize nitrogen and sulfur
soil bacteria
dissimilatory denitrification
reduction of nitrogen for energy yield
ammonia used for respiration
assimilatory nitrification
reduction of nitrate to ammonia for building biomass
sequence of nitrate reduction
nitrate –> nitrite –> nitric oxide –> nitrous oxide –> nitrogen gas
or nitrate –> ammonia + water
sequence of sulfur reduction
sulfate –> sulfite –> thiosulfate –> sulfur –> hydrogen sulfate
dissimilatory metal reduction
reducing metals as TEA
can be used for making electricity in a battery
ex. iron, magnesium
reduced minerals and single-carbon compounds serve as e- donors to the ETS in which type of metabolism?
lithotrophy/chemolithotrophy
is the TEA in lithotrophy a strong oxidant?
yes because most inorganic substrates are poor e- donors compared to glucose
TEA ex. O2, NO3-, Fe3+
obligate lithotroph
consume no organic carbon source
build biomass by fixing CO2
iron oxidation lithotrophy
reduced metal ions like Fe2+ get oxidized to provide energy
this generates metals with higher oxidation states (Fe3+) that other bacteria use for anaerobic respiration
where does iron oxidation happen
low pH like in mines where other microbes oxidize sulfur to sulfuric acid
rusticyanin
a periplasmic protein that collects e- and excludes the metal itself
reverse electron flow
an e- donor reduces an ETS with an unfavorable reduction potential using deltapH as energy source
nitrogen oxidation lithotrophy pathway
ammonium –> hydroxylamine –> nitrite –> nitrate
reduced forms of nitrogen like ammonium derived from fertilizers support the growth of _______
nitrifiers
nitrifiers
bacteria that generate nitrites or nitrates
produces acid that degrades envir. quality –> leech into groundwater
are ammonia/ammonium and nitrite good e- donors compared to organic molecules?
no, requires making NADPH (instead of NADH) via reverse e- flow
anammox reaction
anaerobic ammonium oxidation NH4 + NO2 –> N2 + H2O
used in wastewater treatment to eliminate ammonium
in the ocean, these bacteria cycle 1/2 N2 gas
anammoxosome
organelle containing anammox rxn enzymes
sulfur oxidation produces…
sulfuric acid which causes severe envir. acidification
leeching
microbial metal dissolution from ores
hydrogenotrophy uses __ as an e- donor
H2
ex. oxidation of H2 by sulfur to make H2S
is H2 is strong e- donor?
yes, more so than glucose
3 classifications of hydrogenotrophy depending on what H2 reduces
O2 = lithotrophy
organic TEA = fermentation or anaerobic respiration
sulfur = anaerobic lithotrophy
dehalorespiration
hydrogenotrophy that bioremediates areas
halogenated organic molecules accept e- from H2
ex. chlorinated moelcules
methanogenesis
reduction of CO2 and other 1c compounds to methane
done by archaea called methanogens
methanogenesis and methylotrophy
methanogens make methane and methylotrophs (soil bacteria) uses it for oxidation
phototrophy
converting light energy to chemical energy using photoexcitation or pigments
bacteriorhodopsin protein in haloarchaea membrane
light-driven photoexcitation and relaxation pumps protons
absorb light –> conformational change to cis and pump H+
archaea version of retinal-based proton pump
halobacterium salinarium archaea purple membrane
pack entire membrane with bacteriorhodopsin
protein trimers make purple membrane
proteorhodopsin
bacteria version of retinal-based proton pump
found in 13% of marine bacteria using metagenomics
retinal
cofactor that in bacteriorhodopsin attached to N end of lys
photoheterotrophy
light absoprtion and heterotrophy
how are light rays captured
spreading the pigment photoreceptor that absorbs them over the surface of the membrane
chlorophyll
pigment that contains a chromophore light absorbing e- carrier
many types alter absorption spectra
antenna complex
group of chlorophyll like a satellite dish around a reaction center that connects to ETC
antenna complex of cyanobacteria
phycobilisome
thylakoids
extensive foldings of photosynthetic membrane
F1F0 embedded here
anaerobic photosystem I
receives e- from H2S or iron
green sulfur bacteria
anaerobic photosystem II
returns e- from ETS to bacteriochlorophyll
purple bacteria
oxygenic Z pathway
homologs of PSI and PSII
cyanobacteria and chloroplasts of green plants
4e- from H2O to make O2
PSI pathway
excited e- separated from H2S or Fe and transferred to feredoxin (higher reduction potential)
make NADH and fix CO2
PSII pathway
cyclic photophosphorylation
not enough E to make NADH, makes NADPH using reverse e- flow
oxygenic Z pathway
PSII rxn provides E to split water and make O2
4 H+ pumped and 3 ATP/O2 made
e- from PSII cycle to PSI by plastocyanin and make NADH
