Lecture 4: Anaerobic Respiration

anaerobic means in the _____ of oxygen

absence

respiration involves the _____ for the creation of a _____

ETC; proton motive force

what is the benefit of doing anaerobic respiration?

allows the organisms to fill niches where oxygen is not abundant (while other molecules ARE)

anaerobic respiration is the use of an electron _____ other than oxygen in an electron-transport-based _____ and leading to a _____

acceptor; oxidation; PMF

sometimes instead of a PROTON motive force, organisms can make a _____ motive force

sodium

anaerobic respiration is generally not found in _____ (domain of life)

eukaryotes

in eukaryotes, _____ are the site of respiration

mitrochondrias

what is one example of a eukaryote that DOES do anaerobic respiration?

globobulimina —> protist that does denitrification

bacteria and archaea can use an enormous _____ of electron acceptors

diversity

what is an obligate aerobe

organism requires presence of oxygen to grow

what is a microaerophile

organism requires a SMALL level of oxygen to grow/survive

what is a facultative anaerobe

can survive with or without oxygen, but prefers oxygen

what is an aerotolerant anaerobe?

can survive in presence of oxygen, but does not use it

what is an obligate anaerobe?

cannot survive in the presence of oxygen

dissimilatory denitrificiation converts _____ into _____ OR _____

nitrate; nitrite; N2 gas

most organisms that do denitrification will reduce it to _____, what is an example of an organism that does this?

nitrite; E. coli

do you get more energy from reducing nitrate to nitrite or N2?

reducing fully to N2

how many electrons are released when you convert nitrate to nitrite?

2

how many electrons are released when you convert nitrate to N2 gas?

5

almost all organisms who do Dissimilatory denitrification are _____ and most are in the _____ phylum

facultative aerobes; proteobacteria

dissimilatory denitrification is often done by organisms that prefer to use _____

oxygen (its like a backup system)

how might dissimilatory denitrification be helpful for humans?

wastewater treatment

how might dissimilatory denitrification be harmful to humans?

in soil, converting fixed nitrogen to nitrogen gas (that gets put in the atmosphere)

sulfur reduction is typically done by _____

obligate anaerobes

can eukaryotes do sulfur reduction?

no, only bacteria and archaea

what are SRBs?

sulfur reducing bacteria

can sulfate be DIRECTLY reduced?

no, needs to be activated with ATP first

what are the 2 types of sulfur reduction?

sulfate to sulfite, and elemental sulfur to H2S

how many electrons are released when you reduce sulfate to sulfite?

2

how many electrons are reduced when you reduce sulfate to H2S?

8

how many electrons are released when you reduce elemental sulfur to H2S?

2

SRB typically have specialized pathways to _____

activate sulfate

dissimilatory metal reduction is diversely spread _____

phylogenetically (many organisms do this)

what are the two most common metals used in dissimilatory metal reduction?

iron and manganese

why is iron a useful for reduction agent?

Fe3+ is abundant in nature

dissimilatory metal reduction can be both _____ and _____ to humans

helpful; harmful

dissimilatory metal reduction with IRON will convert _____ to _____

Fe3+; Fe2+

dissimilatory metal reduction with MANGANESE will convert _____ to _____

Mn4+; Mn2+

which domain of life has methanogens?

archaea

which domain of life has acetogens?

bacteria

methanogens and acetogens are typically _____ sensitive

oxygen

methanogens can reduce _____ to _____

CO2; CH4 (methane)

acetogens can reduce _____ to _____

CO2; Acetate

what are the 4 most common forms of anaerobic respiration?

dissimilatory denitrification, sulfur reduction, dissimilatory metal reduction, methanogens and acetogens

nitrate reduction and denitrification are very _____ forms of anaerobic respiration

favorable

E. coli does _____, while paracoccus and pseudomonas does _____

nitrate reduction; denitrification

in nitrate reduction, _____ is excreted

nitrite (NO2-)

in denitrification, _____ is released

nitrogen gas

in order for E. coli to do nitrogen reduction, they require a protein called _____ to be present in the _____

nitrogen reductase complex; ETC

denitrification requires _____ proteins that nitrogen reduction

MORE

in addition to nitrogen reductase, organisms that do denitrification require _____, _____, and _____

nitrate reductase, nitric oxide reductase, and nitrous oxide reductase

expression of nitrogen reductase and other genes are oxygen _____ and require sufficient _____ to be present

repressed; nitrate

why wouldn’t an organism express nitrate reductase all the time?

waste of energy to make the protein when oxygen is present (and is a much better acceptor)

some prokaryotes can use nitrate for anaerobic respiration, but produce _____ instead!

ammonia (NH3+)

why does globobulimina do denitrification (its eukaryotic!)?

its found in nitrate rich, oxygen poor environments

nitrification is the conversion of _____ to _____; what domains do this?

ammonium to nitrate; bacteria and archaea

how do you convert ammonium to nitrate? (what are the intermediates)

ammonium —> hydroxylamine → nitrite → nitrate

nitrogen fixation is the conversion of _____ to _____; what domain does this?

ammonium; glutamine (organic N); bacteria

denitrification is the conversion of _____ to _____; what domain typically does this?

nitrate; nitrogen gas; bacteria

denitrification is particularly detrimental to _____

agriculture

how is nitrate converted to nitrogen gas (intermediates)?

nitrate → nitrite → nitric oxide → nitrous oxide → nitrogen gas

assimilation is the conversion of _____ to _____

nitrate; glutamine

anammox is the conversion of _____ AND _____ into ____; what domain typically does this?

nitrite; ammonium; nitrogen gas; bacteria

what are the three most important intermediates in the nitrogen cycle?

nitrite, ammonium, nitrogen gas

nitrifiers and annamox bacteria are examples of _____

chemolithotrophs (use inorganic compounds!)

dissimilatory is _____, while assimilatory is _____

respiration; biosynthesis

in dissimilatory processes, the end product is _____

excreted

in assimilatory processes, the end product is _____

assimilated into the cell material

in dissimilatory processes, _____ amounts are reduced, and this is typically done by _____ organisms

LARGE; prokaryotes

in addimilatory organisms, only the amount needed for _____ is reduced, and this is typically done by _____ organism

biosynthesis; prokaryotes and eukaryotes

in DISSIMILATORY nitrogen reduction, nitrate is reduced to _____

nitrogen gas

in ASSIMILATORY nitrogen reduction, nitrate is reduced to _____

ammonia

assimilatory and dissimilatory proteins/enzymes are _____, despite often doing the SAME thing, why?

different; allows for separate gene expression which allows for more regulation of each pathway

most SRBs use _____ as the electron donor; this is an example of _____

hydrogen; chemolithotrophy

most SRBs are ___(domain)___, but one exception to this is _____

bacteria; archaeoglobus

_____ ATP is produced per SO4 reduced

1

_____ ATP is produced per SO4 with lactate

2

in addition to using H2 as the energy source, SRBs can use _____ to make more hydrogen for reduction

intracellular lactate

in order to use lactate for sulfate reduction, lactase converted to _____ by _____, which released H2 that can be used for the ETC

pyruvate; lactate dehydrogenase

in SRBs: at the beginning of the ETC, H2 gas is converted to _____ which helps make the _____, and the electrons are transferred to the _____

protons; PMF; cytochrome complex

In SRBs: the electrons are transferred from the cytochrome complex to _____

FeS proteins

in order for sulfate to be reduced it needs to be converted to _____

sulfite (SO2-3)

once sulfate is converted to sulfite, it can react with the _____ from _____ proteins to make _____

electrons; FeS; H2S

after the electrons reduce sulfite, _____ or _____ are secreted, which lowers the _____, and can react with _____

sulfide; H2S; pH; metals

in dissimilatroy sulfur metabolism, sulfate is activated with ATP to make _____, in assimilatory metabolism, it reactions with TWO ATP to make _____

APS; PAPS

what two things can APS be used to make?

PAPS; dissimilatory H2S

PAPS is used to make _____ H2S, while APS is used to make _____ H2S

assimilatory; dissimilatory

dissimilatory H2S is _____, while Assimilatory H2S is used to make _____

excreted; organic sulfur compounds

what are two example of organic sulfur compounds made via assimilatory sulfur metabolism

cysteine, methionine

assimilatory sulfur metabolism is a way to can acquire sulfate from the _____ for _____ needs

environment; biosynthetic

SRBs found underground can react with _____

oil deposits

if you burn oil that contains _____ from sulfur cycling, this results in _____ which is found in _____ rain

H2S; H2SO4; acid

what is H2SO4?

sulfuric acid

fermenting bacteria found in sewer can produce _____ which is utilized by SRB, making _____ as a waste product. In aerobic sections of the pipe, this molecule can reaction with _____ to make _____ that leads to; ultimately this is a problem because it causes sewer pipe _____

H2; H2S; oxygen; sulfate; corrosion

via _____, CO2 is reduced to CH4, which is a _____

methanogenesis; greenhouse gas

_____ is a major component of the Earth’s crust?

Fe3+

why is Fe3= limited to organisms?

at neutral pH, it is a precipiate

Fe2+ is _____, while Fe3+ is _____

soluble; precipitates

_____ are a major source of Fe to other organisms

Femic iron reducers

Fe3+ is reduced to Fe2+ which is _____ via _____, this makes it more available for _____

soluble; anaerobic respiration; other organisms