BIMM 120 Lecture13.MicrobialEcologyI.051211

BIMM 120 Lecture13.MicrobialEcologyI.051211 - BIMM 120...

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BIMM 120 Announcements BIMM 120 Announcements Paper #2 is available on WebCT – we will discuss in class on Tues 5/17 Gorby YA et al. (2006) Electrically conductive bacterial nanowires produced by Shewanella oneidensis strain MR-1 and other microorganisms. Proc Natl Acad Sci USA 103:11358
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Lecture 12 Phototrophy Photosynthesis CO 2 fixation pathways N 2 fixation fixation The biological reduction of atmospheric dinitrogen (N 2 ) to ammonia (NH 3 ) by the nitrogenase enzyme Chemolithotrophy Chemolithotrophy Sulfur Oxidation & Iron Oxidation
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Chemolithotrophy Chemolithotrophy Energy & Electrons from the oxidation of inorganic compounds Chemolithoautotrophs Chemolithoautotrophs Chemolithoheterotrophs Chemolithoheterotrophs inorganic electron donor sources are diverse inorganic electron donor sources are diverse geological, biological, anthropogenic (“mixotrophs”) source of carbon = organics * * * Energy production proceeds via Reducing power comes directly from inorganic donor or reverse e - flow electron acceptors can be diverse as well electron acceptors can be diverse as well recall the diversity of respirations discussed in Lecture 11. .. source of carbon = CO 2 (most common)
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inorganic electron donors inorganic electron donors : H : H 2 , HS , HS - , S , S o , NH , NH 4 , NO , NO 2- , Fe , Fe 2+ , etc. , etc. Energy calculations allow prediction of the metabolism of chemolithotrophs in nature (it’s all about the redox tower. ..again) electron acceptors electron acceptors : O : O 2 , SO , SO 4 2- , NO , NO 3- , metals, organics, etc. , metals, organics, etc. Diversity of Diversity of Chemolithotrophs Chemolithotrophs these organisms are at the heart of global biogeochemical cycling processes (Lecture 14) Beggiatoa filamentous S-oxidizers H 2 S Æ SO 4 2- O 2 acidophilic Fe oxidizers Fe 2+ Æ Fe 3+ O 2 Nitrobacter nitrifying bacterium NO 2 - Æ NO 3 - nitrite oxidase O 2
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Oxidation of Reduced Sulfur Compounds Oxidation of Reduced Sulfur Compounds most are aerobic; some can use NO 3 - Electrons from S oxidation feed into electron transport chain (PMF = ATP synthesis) Reverse electron flow necessary for NAD(P)H production ‘cuz e - donors are more positive than NAD + (just like anoxygenic photosynthesis) 3 separate pathways for sulfur oxidation are known. ..(e.g. Sox) CO 2 fixation proceeds via Calvin Benson cycle or reverse TCA H 2 S, S o or S 2 O 3 2- Æ SO 4 2- H 2 S Why is Reverse Electron Flow necessary? Remember that electrons always “fall down” the redox tower!
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BIMM 120 Lecture13.MicrobialEcologyI.051211 - BIMM 120...

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