Lecture 32 - Bacterial Energy metabolism 1

Question 1

How many cells are on the average human

Answer 1

3.0 x10^13

Question 2

What are the key features of bacterial organelle-like structures

Answer 2

Often intracytoplasmic membrane systems
Often invaginations of the cytoplasmic membrane

Increase surface area and facilitate metabolic activities
Photosynthesis, nitrification, ammonium or methane oxidation, etc.

Sometimes proteinaceous compartments
Protein-based structures

Create chemically distinct compartments and gradients

No nucleus

Question 3

What do chlorosomes do

Answer 3

Site of photosynthesis in green sulphur bacteria

Question 4

What are thylakoids (pbacteria)

Answer 4

site of photosynthesis in cyanobacteria

Question 5

What are Magnetosomes

Answer 5

enable bacteria to align with geomagnetic fields (magnetotaxis)

Question 6

What are acidocalsisome

Answer 6

Site of polyphosphate and calcium storage

Question 7

What do carboxysomes do

Answer 7

proteinaceous shells enclose RuBisCO and carbonic anhydrase, enhancing CO₂ fixation)

Question 8

What do gas vesicles provide

Answer 8

buoyancy to move cells up and down a water column

Question 9

What is the endosymbiosis theory

Answer 9

engulfing o bacteria lead to mitochondria and chloroplasts

Question 10

How are bacteria classified by cell wall

Answer 10

Gram positive anf gram negative

Question 11

Why is 95-99% of microbial species in the environment not readily cultivatable

Answer 11

Physiological requirements are unknown or highly specific

Interdependencies require complex mixed culture

Question 12

How are bacteria metabolically classified

Answer 12

Energy source - chemotroph or phototroph

Carbon source - Photoauto, photohetero, mixo and chemolithoautotrophic

Question 13

What do bacteria need energy for

Answer 13

Growth, maintenance and reproduction
Biosynthesis, transport, motility, etc

Question 14

Conditions

Answer 14

Aerobic – presence of O2 (aerobic conditions)
Anaerobic – absence of O2 (anoxic conditions)

Question 15

What does chemoorganotrophy mean

Answer 15

Energy from chemicals

Chemicals are organic compounds

Question 16

What does chemolithotrophy mean

Answer 16

Energy from chemicals
The chemicals are inorganic compounds

Chemolithoheterotroph from organic sources (heterotrophic)
Chemolithoautotrophy from CO2 (autotrophic)

Question 17

What are some chemolitotrophic e- donors

Answer 17

Hydrogen
Sulfur compounds
ammonia
nitrate
iron
arsenite

Question 18

What is mixotrophy

Answer 18

Obtain energy and carbon from a combination of autotrophic and heterotrophic processes

A broad and flexible metabolic strategy
Switch between or use simultaneously depending on environmental conditions

Photoautotrophy + chemoorganotrophy
Photoautotrophy + photoheterotrophy
Chemolithoautotrophy + chemoorganotrophy

Question 19

What is autotrophy

Answer 19

Most autotrophs use the Calvin cycle to fix CO2

Alternative pathways are reverse TCA cycle, reductive acetyl-CoA pathway, and 3-hydroxypropionate bi-cycle

Question 20

What is the reverse electron flow

Answer 20

Chemolithotrophs still need ATP and NAD(P)H

But many inorganic e- donors have redox potentials higher than NAD(P)+ and NAD(P)H

e- are transferred to coenzyme Q or a cytochrome and then;
Some generate a proton motive force when passed to a terminal e- acceptor
Forward e- transport
Some are passed to NAD(P)+ to make NAD(P)H using the proton motive force
Reverse e- transport
Takes 5x forward pathway to power 1x reverse pathway