Chemolithotrophy

What is a shortcoming of iron oxidation?

Doesn't yield much energy so a lot of iron must be oxidized

How does FeOB prevent itself from being encased in oxidized irons?

They form a stalk.

What is the requirement for oxygen reduction to be coupled to iron oxidation at pH 7?

Oxygen level must be low enough that biological iron oxidation is faster than abiotic iron oxidation

What is the energy source for generation of NADH in sulfur oxidation?

PMF

Why do sulfur-oxidizing bacteria live in acidic environment?

Protons are a byproduct of most sulfur oxidations

PMF is generated during sulfur oxidation when electrons are transferred from ______ and when _____.

Q cycle to cyt bc1, O2 is reduced

In FeOB at low pH, all electrons enter at a greater reduction potential than NAD+/NADH couple. What does this suggest?

Reverse electron flow is required to generate NADH at the expense of PMF

Why is a lot of iron oxidation required at low pH environment?

The reduction potentials of iron and oxygen are very similar, so small amount of energy per electron is yielded.

H2 oxidizers are (aerobes, anaerobes, can be both).

can be both

How do H2 oxidizing aerobes get their carbon source?

carbon fixation or from organic molecules

When organic carbon sources are present, aerobic H2 oxidizers are preferentially (chemolithotrophs/chemoorganotrophs).

chemoorganotrophs

At neutral pH, FeOB can directly reduce _____ to initiate electron transport reactions, generating a _____. Reverse electron flow is (required/not needed) to generate NADH.

cyt c, PMF, required

Some H2 oxidizers also make ______, which reduces NAD+ to NADH that can be used for biosynthetic reduction reactions. This reactions (does/does not) contribute to the PMF

cytoplasmic hydrogenase, does not

How does chemolithotrophs in general obtain their reducing power?

from inorganic compound or from reverse electron transport

Chemolithotrophs must use reverse electron flow if an electron donor has a (higher/lower) E0' than NAD+/NADH to generate NADH.

higher

Sulfide donates electrons at a (higher/lower) reduction potential than sulfite.

lower

Sulfide yields (more/less) PMF than sulfite.

more

At which pH is FeOB more likely to live in anoxic or microoxic environments?

neutral pH

What is the only viable electron acceptor for FeOB at pH 2 environment?

oxygen

FeOB can couple iron oxidation to _____

oxygen reduction or nitrate reduction

The name of the periplasmic carrier in FeOB in low pH environment

rusticyanin

Why is reverse electron flow needed in sulfur oxidation to generate NADH?

Electrons from sulfide and sulfite are at higher reduction potential than NAD+/NADH couple.

What waste product is formed because of iron oxidation at low pH?

Fe(OH)3

What is the problem for FeOB with oxygen in pH 7 environment?

Fe2+ can spontaneously oxidized into Fe3+ by abiotic reaction

Sugars repress which genes for aerobic H2 oxidizers?

Genes for H2 oxidation and carbon fixation

Fate of electrons from H2 in H2 oxidation

H2, membrane-integrated hydrogenase, quinone cycle, cyt bc1, cyt c, cyt aa3, oxygen

How is iron remained at the extracellular space during iron oxidation at low pH?

Iron is oxidized by the outer membrane cyt c

(T/F) Aerobic H2 oxidizers can also be chemoorganotrophs as well as chemolithotrophs

true