Lecture 24

Question 1

Microbe that is an excellent example of a microbe that can perform many types of metabolisms

Answer 1

E. coli

Question 2

Electron transport and oxidative phosphorylation are basically the same in anaerobes as in aerobes with minor variations in what?

Answer 2

The final electron acceptor, and different electron carrier proteins found in the ETC

Question 3

In anaerobic respiration, the final hydrogen/electron acceptor is some other inorganic molecule, such as? How many ATP produced?

Answer 3

nitrate (NO3-), sulfate (SO4^2-), nitrite (NO2-), carbonate (CO3^2-)

-more than 2, but less than 38 ATP produced

Question 4

Energy generation for anaerobic respiration is still by…

Answer 4

oxidative phosphorylation and SLP

Question 5

When an ORGANIC molecule is the final e- acceptor the process is called what? This can occur under ______ and ______ events. How many ATP are produced?

Answer 5

fermentation, this can occur under aerobic and anaerobic conditions

-2 ATP are made during this process

Question 6

E. coli chart of different energy generating processes. These adaptations allow E. coli to inhabit its natural intestinal (anaerobic conditions) and its extra-intestinal/or outside the intestine (aerobic or anaerobic) habitats.

Answer 6

?? E. coli can produce energy regardless of the growth conditions. E. coli will grow slower during fermentation (anything that produces less ATP will result in slower growth).

Question 7

______ is one of the most common anaerobic e- acceptors and can be reduced to:

Answer 7

Nitrate

nitrite NO2-, nitric oxide NO, nitrous oxide N2O, or dinitrogen/nitrogen gas N2

Question 8

Some organisms can also use sulfate SO4^2- as the final e- acceptor to form

Answer 8

H2S (hydrogen sulfide)

Question 9

bacteria using nitrate and sulfate as final electron acceptors is essential for what?

Answer 9

nitrogen and sulfur cycles that occur in nature

Question 10

Archaea can use ______ as the e- acceptor and reduct it to ______ gas. This is a special type of metabolism called what?

Answer 10

can use CO2, and reduce it to methane gas CH4

called Methanogenesis

Question 11

Some microbes that are able to use various _______ as electron acceptors, such as what?

Answer 11

various metals, such as ferric ion Fe 3+, selenite?, maganic

Question 12

Nitrate respiration. The final e- acceptor is? What are the complexes here

Answer 12

e- from NADH is transferred to Cytochrom b/c1 complex, and then to quinone pool (Q, QH2), then to nitrate reductase (membrane oxidase complex) resulting in the transport of protons across the membrane – generation of PMF to produce ATP

Question 13

Equation for nitrate (reduction) respiration

Answer 13

NO3- + 2e- + 2H+ –> NO2- + H2O

Question 14

The produce of nitrate respiration is either ________ or could be further reduced to what?

Answer 14

excreted or further reduced to ammonia

Question 15

Bacteria that is able to completely reduce Nitrate to dinitrogen gas (N2). Types of this bacteria

Answer 15

denitrifying bacteria. Eg. Pseudomonas stutzeri and Paracoccus species

Question 16

Denitrification:

first NADH is oxidized, and electron goes through what?

Answer 16

DH (dehydrogenase complex) - proton pumped out here

Question 17

from DH what happens to e-

Answer 17

electron is transferred to the quinone pool Q

Question 18

from quinone pool Q, what happens to the electron? here what happens to nitrate?

Answer 18

it is passed to the cytochrome oxidase (quinol oxidase) nitrate reductase

nitrate is reduced to nitrite and water

Question 19

in denitrification some e- may be shuttled instead to a _________ complex. Here something else happens?

Answer 19

cytochrome b/c complex. More protons are pumped into the periplasmic space

Question 20

1. from cytochrome b/c complex during denitrification, some of the electrons are shuttled to _________, and _______ ends up being reduced to ______ and water.

Answer 20

nitrite reductases, and end up reducing nitrite NO2- to nitrous oxide N2O and water.

Question 21

2. from cytochrome b/c complex during denitrification, some of the electrons are shuttled to _________, and _______ ends up being reduced to ______ and water.

Answer 21

nitrous oxide reductases that will be used to reduce nitrous oxide N20 to dinitrogen N2 gas

Question 22

The synthesis of these reductases (nitrate, nitrite, etc) are ________ and their activities ______ by oxygen.

Answer 22

repressed, and activities inhibited by oxygen

Question 23

Alternative electron acceptors like nitrate, sulfate, etc. do not have as ______ a reduction potential as ______ .

Answer 23

positive, oxygen

Question 24

Most of these metabolic capabilities are not associated with any one phylogenetic group (with the exception of?), but are found scattered among the various groups of ________ .

Answer 24

exception of methanogenesis (archaea)

bacteria

Question 25

MR-1 and a special type of bacteria

Answer 25

MR-1 stands for metal reducing, and a bacteria that is being studied currently for it’s bioremediation possibilities is Shewanella oneidensis