8.1. Bacterial Diversity in The Sulfur Cycle

Question 1

T/F

Sulfur metabolism gave rise to the earliest forms of life on earth

Answer 1

true

Question 2

Microorganisms in the sulfur cycle can perform 2 types of metabolisms:

Answer 2

1. assimilative metabolism
2. dissimilative metabolism

Question 3

Assimilative metabolism=

Answer 3

oxidation of sulfur compounds –> creates organic sulfur compounds for the organism to use

Question 4

Dissimilative metabolism=

Answer 4

reduction of sulfur compounds –> get energy from sulfur compounds (respiration)

Question 5

Why is there such huge diversity in the sulfur cycle?

Answer 5

Because of the chemistry of sulfur
- 8 oxidation states
- sulfur has forms that can be e- acceptors and forms that can be e- donors

Question 6

List the 5 types of organisms (Bacteria and Archaea) that control the sulfur cycle

Answer 6

1. purple sulfur bacteria
2. green sulfur bacteria
3. sulfate reducers
4. sulfur reducers
5. sulfur oxidizers

• 1 and 2 are anoxygenic phototrophs, which we covered in lecture 7

Question 7

What energy sources (2) do sulfate reducers use? Is this energy source an e- acceptor or donor?

Answer 7

• H2
• organic compounds

electron donor

Question 8

Euryarchaeota are _____ _______ (reducers/ oxidizers)

Answer 8

sulfate reducers

Question 9

Which bacteria are sulfate reducers?

Answer 9

• proteobacteria (1 group)
• firmicutes

Question 10

Where do sulfur products sit on the “bad-good for energy” continuum?

Answer 10

mild-bad for energy (near the mid-top of the list)

Question 11

What alternative metabolisms could sulfate reducers use?

Answer 11

• Nitrate reduction
• Fermentation

Question 12

T/F

Sulfate reducers are obligatory anaerobes

Answer 12

true
(sulfate respiration)

ie they cannot use oxygen

Question 13

Sulfate reducers use:
and produce:

Answer 13

use
H2 or organic compounds like lactate (they’re able to use hydrocarbons)

produce
H2S as a metabolic product of sulfate respiration

Question 14

List 6 famous bacteria sulfate reducers

Answer 14

• desulfomonas
• desulfotomaculum
• desulfobacter
• desulfovibro
• thermodesulfobacterium
• thermodesulfovibrio

Question 15

List 1 famous sulfate reducer from Archaea

Answer 15

archaeoglobus

Question 16

Describe the sulfate reducer “desulfotomaculum”.
- Where does it live? How do we use it?

Answer 16

• Lives in soils
• Found in canned foods= responsible for the smell
• Forms endospores (dormant alternate life forms)

Question 17

What do the following organisms all have in common?
- thermodesulfobacterium
- thermodesulfovibrio
- archaeoglobus

Answer 17

• sulfate reducers
• thermophilic
• found in geothermally heated enviros like hot springs

Question 18

Describe the ecology of sulfate reducers:
- Found in _____ (oxic/ anoxic) areas
- abundant in marine ____
- responsible for the ______ ____ smell in marine areas

Answer 18

• anoxic
• sediments
• rotten egg

Question 19

T/F
Desulfovibrio are one of the few sulfate-reducing bacteria that are not present in the human gut

Answer 19

False

Desulfovibrio are present in the human gut –> they produce H2S, which reacts with Fe2+ in the gut to form a black precipitate and spread colonies

Question 20

What energy source do sulfur reducers use?

Answer 20

H2 and organic compounds
- eg. acetate, succniate, formate, ethanol, propanol

Question 21

Which bacteria/ archaea are sulfur reducers?

Answer 21

Bacteria: 3 groups of proteobacteria
Archaea: Chrenarchaeota

Question 22

T/F
Sulfur reducers are obligatory aerobes

Answer 22

false

they’re obligatory ANAEROBES (sulfur respiration)

Question 23

Sulfur reducers can be ____ _____ as an alternative metabolism

Answer 23

facultative aerobics

Question 24

List 5 famous sulfur reducers
(2 Bacteria, 3 Archaea)

Answer 24

Bacteria:
- desulfomonas
- sulfospirillim

Archaea:
- thermoproteales
- sulfolobales
- mathanogens

Question 25

Would it make sense to find sulfur reducers in close proximity to sulfate reducers?

Answer 25

Yes because they use similar compounds to generate energy

Question 26

Sulfur reducers use __ to create ___, which is then used by anoxygenic phototrophs

Answer 26

S H2S

Question 27

Sulfur oxidizers use ____ as an energy source (e- ____)

Answer 27

H2S and S donor

Question 28

Which bacteria and archaea are sulfur oxidizers?

Answer 28

Bacteria: 3 groups of proteobacteria Archaea: crenarchaeota

Question 29

Give 2 alternative metabolisms that sulfur oxidizers can use

Answer 29

- organic compounds as energy source - deposit of sulfur granules that can be used if H2S is exhausted

Question 30

Sulfur oxidizers are chemolithotrophs, meaning:

Answer 30

they use inorganic compounds to extract energy

Question 31

List 4 famous sulfur oxidizers (2 bacteria, 2 archaea)

Answer 31

Bacteria: - thiobacillus - acidithiobacillus ferrooxidans Archaea: - sulfolobus - metallosphaera sedula

Question 32

Acidithiobacillus ferrooxidans uses ___ as its electron donor

Answer 32

FES2

Question 33

thiobacillus uses ___ or ___ and produces ___ ____. This is the best studied one!

Answer 33

H2S or S sulfuric acid

Question 34

How is Acidithiobacillus ferrooxidans beneficial for mining?

Answer 34

Acidithiobacillus ferrooxidans oxidizes FES2: releases iron from sulfur. = iron is extracted from ores, which helps us

Question 35

Bioleaching=

Answer 35

metal extraction from ores via microorganisms - beneficial for mining - used for lots of different metals - example for iron: Acidithiobacillus ferrooxidans (sulfur oxidizer)

Question 36

How is Acidithiobacillus ferrooxidans harmful for mining?

Answer 36

Bioleaching releases iron from sulfur, but also other metals are released. Can cause acidification, and release of toxic metals

Question 37

Many sulfur oxidizers evolved to use ___ as a donor and ___ as an acceptor. Why is this surprising?

Answer 37

H2S O2 Because H2S and O2 are VERY reactive together. This is possible due to ecological strategies they developed

Question 38

There are 3 possible explanations for how sulfur oxidizers evolved to use H2S and O2. What are they?

Answer 38

1. O2 dependent positioning (in Bacteria Beggiatoa) 2. Anaerobic vacuole 3. Symbiotic Association

Question 39

Explain how O2 dependent positioning could explain how sulfur oxidizers evolved to use H2S and O2.

Answer 39

- cyanobacteria produce O2 in photosynthesis (daytime) on top of microbial mats -Beggaitoa on the bottom in daytime, and goes to top during nightime to get O2. = H2S oxidized and O2 reduced to produce energy

Question 40

Explain how anaerobic vacuoles could explain how sulfur oxidizers evolved to use H2S and O2.

Answer 40

Thiomargarita Bacteria uses H2S and NO3- (nitrite respiration) Process occurs in vacuole - storage of sulfur and ammonium: bacteria used S and O2 instead of H2S and O2

Question 41

Explain how symbiotic association could explain how sulfur oxidizers evolved to use H2S and O2.

Answer 41

Yeti crab= eukaryotic host - host regulates levels of H2S and O2 (balancing) - bacterium fixes CO2 for the host