8.1. Bacterial Diversity in The Sulfur Cycle
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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