8.1. Bacterial Diversity in The Sulfur Cycle Flashcards
T/F
Sulfur metabolism gave rise to the earliest forms of life on earth
true
Microorganisms in the sulfur cycle can perform 2 types of metabolisms:
- assimilative metabolism
- dissimilative metabolism
Assimilative metabolism=
oxidation of sulfur compounds –> creates organic sulfur compounds for the organism to use
Dissimilative metabolism=
reduction of sulfur compounds –> get energy from sulfur compounds (respiration)
Why is there such huge diversity in the sulfur cycle?
Because of the chemistry of sulfur
- 8 oxidation states
- sulfur has forms that can be e- acceptors and forms that can be e- donors
List the 5 types of organisms (Bacteria and Archaea) that control the sulfur cycle
- purple sulfur bacteria
- green sulfur bacteria
- sulfate reducers
- sulfur reducers
- sulfur oxidizers
- 1 and 2 are anoxygenic phototrophs, which we covered in lecture 7
What energy sources (2) do sulfate reducers use? Is this energy source an e- acceptor or donor?
- H2
- organic compounds
electron donor
Euryarchaeota are _____ _______ (reducers/ oxidizers)
sulfate reducers
Which bacteria are sulfate reducers?
- proteobacteria (1 group)
- firmicutes
Where do sulfur products sit on the “bad-good for energy” continuum?
mild-bad for energy (near the mid-top of the list)
What alternative metabolisms could sulfate reducers use?
- Nitrate reduction
- Fermentation
T/F
Sulfate reducers are obligatory anaerobes
true
(sulfate respiration)
ie they cannot use oxygen
Sulfate reducers use:
and produce:
use
H2 or organic compounds like lactate (they’re able to use hydrocarbons)
produce
H2S as a metabolic product of sulfate respiration
List 6 famous bacteria sulfate reducers
- desulfomonas
- desulfotomaculum
- desulfobacter
- desulfovibro
- thermodesulfobacterium
- thermodesulfovibrio
List 1 famous sulfate reducer from Archaea
archaeoglobus
Describe the sulfate reducer “desulfotomaculum”.
- Where does it live? How do we use it?
- Lives in soils
- Found in canned foods= responsible for the smell
- Forms endospores (dormant alternate life forms)
What do the following organisms all have in common?
- thermodesulfobacterium
- thermodesulfovibrio
- archaeoglobus
- sulfate reducers
- thermophilic
- found in geothermally heated enviros like hot springs
Describe the ecology of sulfate reducers:
- Found in _____ (oxic/ anoxic) areas
- abundant in marine ____
- responsible for the ______ ____ smell in marine areas
- anoxic
- sediments
- rotten egg
T/F
Desulfovibrio are one of the few sulfate-reducing bacteria that are not present in the human gut
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
What energy source do sulfur reducers use?
H2 and organic compounds
- eg. acetate, succniate, formate, ethanol, propanol
Which bacteria/ archaea are sulfur reducers?
Bacteria: 3 groups of proteobacteria
Archaea: Chrenarchaeota
T/F
Sulfur reducers are obligatory aerobes
false
they’re obligatory ANAEROBES (sulfur respiration)
Sulfur reducers can be ____ _____ as an alternative metabolism
facultative aerobics
List 5 famous sulfur reducers
(2 Bacteria, 3 Archaea)
Bacteria:
- desulfomonas
- sulfospirillim
Archaea:
- thermoproteales
- sulfolobales
- mathanogens
Would it make sense to find sulfur reducers in close proximity to sulfate reducers?
Yes because they use similar compounds to generate energy
Sulfur reducers use __ to create ___, which is then used by anoxygenic phototrophs
S
H2S
Sulfur oxidizers use ____ as an energy source (e- ____)
H2S and S
donor
Which bacteria and archaea are sulfur oxidizers?
Bacteria: 3 groups of proteobacteria
Archaea: crenarchaeota
Give 2 alternative metabolisms that sulfur oxidizers can use
- organic compounds as energy source
- deposit of sulfur granules that can be used if H2S is exhausted
Sulfur oxidizers are chemolithotrophs, meaning:
they use inorganic compounds to extract energy
List 4 famous sulfur oxidizers (2 bacteria, 2 archaea)
Bacteria:
- thiobacillus
- acidithiobacillus ferrooxidans
Archaea:
- sulfolobus
- metallosphaera sedula
Acidithiobacillus ferrooxidans uses ___ as its electron donor
FES2
thiobacillus uses ___ or ___ and produces ___ ____.
This is the best studied one!
H2S or S
sulfuric acid
How is Acidithiobacillus ferrooxidans beneficial for mining?
Acidithiobacillus ferrooxidans oxidizes FES2: releases iron from sulfur.
= iron is extracted from ores, which helps us
Bioleaching=
metal extraction from ores via microorganisms
- beneficial for mining
- used for lots of different metals
- example for iron: Acidithiobacillus ferrooxidans (sulfur oxidizer)
How is Acidithiobacillus ferrooxidans harmful for mining?
Bioleaching releases iron from sulfur, but also other metals are released.
Can cause acidification, and release of toxic metals
Many sulfur oxidizers evolved to use ___ as a donor and ___ as an acceptor. Why is this surprising?
H2S
O2
Because H2S and O2 are VERY reactive together. This is possible due to ecological strategies they developed
There are 3 possible explanations for how sulfur oxidizers evolved to use H2S and O2. What are they?
- O2 dependent positioning (in Bacteria Beggiatoa)
- Anaerobic vacuole
- Symbiotic Association
Explain how O2 dependent positioning could explain how sulfur oxidizers evolved to use H2S and O2.
- 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
Explain how anaerobic vacuoles could explain how sulfur oxidizers evolved to use H2S and O2.
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
Explain how symbiotic association could explain how sulfur oxidizers evolved to use H2S and O2.
Yeti crab= eukaryotic host
- host regulates levels of H2S and O2 (balancing)
- bacterium fixes CO2 for the host
