北京大学：《微生物学》课程PPT教学课件（英文版）Chapter 17 Microbial Ecology 2

Chapter 17 Microbial Ecology 2 Methane and methanogenesis Rumen microbial ecology Biogeochemical cycles: nitrogen Biogeochemical cycles: sulfur Biogeochemical cycles: iron Microbial leaching Biogeochemical cycles: trace metals and mercury Petroleum and natural gas(methane) biodegradation Biodegradation of xenobiotics Sewage and wastewater micro biology Plant-microorganism interactions: Crown and gall and hairy root Root nodule bacteria and symbiosis with legumes

Chapter 17 Microbial Ecology 2 Methane and methanogenesis Rumen microbial ecology Biogeochemical cycles: nitrogen Biogeochemical cycles: sulfur Biogeochemical cycles: iron Microbial leaching Biogeochemical cycles: trace metals and mercury Petroleum and natural gas (methane) biodegradation Biodegradation of xenobiotics Sewage and wastewater microbiology Plant-microorganism interactions: Crown and gall and hairy root Root nodule bacteria and symbiosis with legumes

Methanogenesis and Syntrophy Methane production is carried out by a group of Archaea, the methanogens, which are obligate anaerobes. 4H2+CO2CH4+2H20 △G0’=-130kJ/ reaction Substrates microbially converted to methane: methanol, formate, methylcaptan(CH3SH), acetate and methylamines

Methanogenesis and Syntrophy Methane production is carried out by a group of Archaea, the methanogens, which are obligate anaerobes: 4 H2 + CO2 CH4 + 2H2O DGo ’= -130 kJ/reaction Substrates microbially converted to methane: methanol, formate, methylcaptan (CH3SH), acetate and methylamines

Complex polymers A noXIc Cellulose other polysaccharides proteins Cellulolytic and Decomposition other hydrolytic Hydrolysis Various groups of Monomers Sugars. fermentative amino acds Fermentative Fermentation bactera anaerobes act Propionate together in the Butyrate H+ cO Succinate conversion of Reproducing Aceto atty.acid anIc acetogensgenesis Fermentation complex orga bacteria (syntrophs) Methano Acetate materials ultimately cate to methane and co2 Methanogenesis CHa

Anoxic Decomposition Various groups of fermentative anaerobes act together in the conversion of complex organic materials ultimately to methane and CO2

Primary fermenters and Secondary fermenters Primary fermenters: consume glucose to a variety of fermentation products(acetate propionate, butyrate, succinate, alcohols hydrogen and CO2 Secondary fermenters: key organisms in the conversion of complex organic materials to methane(espacially the H2-producing fatty acid oxidizing bacteria)

Primary fermenters and Secondary fermenters Primary fermenters: consume glucose to a variety of fermentation products (acetate, propionate, butyrate, succinate, alcohols, hydrogen and CO2. Secondary fermenters: key organisms in the conversion of complex organic materials to methane (espacially the H2-producing fatty acid￾oxidizing bacteria)

Syntrophy Syntrophy: eating together Syntrophomonas and Syntrophobacter H2 producers, collectively referred to as syntrophs, dependent on syntrophic relationships with other bacteria(in this case, H2-consuming bacteria

Syntrophy Syntrophy: eating together. Syntrophomonas and Syntrophobacter: H2 producers, collectively referred to as syntrophs, dependent on syntrophic relationships with other bacteria (in this case, H2-consuming bacteria)

Microorganisms from the hindgut of the termite Zootermopsis angusticolis Sources of atmospheric methane(biogenic) Ruminants Paddy fields Swamps ermines Ocean /Lakes Others i Abiogenic

Microorganisms from the hindgut of the termite Zootermopsis angusticolis Sources of atmospheric methane (biogenic): Ruminants Paddy fields Swamps Termites Ocean/Lakes Others Abiogenic

Rumen Microbial ecosystem Rumen Esophagus 食道 Small intestine Reticulum 蜂巢胃 Omasum Rumen 重瓣胃 (a) Abomasum 皱胃 Herbivorous mammals that possess a special organ, the rumen are called ruminants. Within rumen, digestion of cellulose and other plant polysaccharides occurs through activities of microorganisms

Rumen Microbial Ecosystem Herbivorous mammals that possess a special organ, the rumen are called ruminants. Within rumen, digestion of cellulose and other plant polysaccharides occurs through activities of microorganisms 食道 蜂巢胃 重瓣胃 皱胃

Biochemical reactions Feed in the rumen Cellulose, starch, and so on Cellulolysis, amylolysis Fermentation Gluco 知 Formate Lactate Succinate H2+ cOz Propionate+ cO2 Acetate Travel across rumen wall Propionate to bloodstream Removed by eructation to Bu strate atmosphere Overall stoichiometry of rumen fermentation 5759uc 65 acetate+ 20 propionate+ 15 butyrate+60 CO, +35 CHe+25,O

Biochemical reactions in the rumen

Biogeochemical Cycles Nitrification Nitrogen NO Nitrobacter Nitrosomonas aorNH2 groups Cyano of protein Rhizobium NO Azoth Beijerinckii Oxic Anoxic lation groups Nitrogen N protein fixation De Clostridium pasteurianum Pseudomonas, Bacillus and other facultative NO Anoxygenic phototrophic NO N2 bacteria aerobes Denitrification

Biogeochemical Cycles: Nitrogen

Atmospheric Nz 3800000 Biological Industrial Combustion Biolo fixation fixation Lightning fixation fixation Lightning 0.004/year 0. 14/year, 0.036/year 0.004/year 0. 10/ear Land Oceans Plants Plants 12 02 03 Dead organic Dead organic 9。os 300 550 Ammonification Ammonification Nitrification Nitrification NH Inorganic 0.008 year 0.005year Inorganic 16 577 Rivers sedimentation Sediments 400.000 0.00025/ year NHa The Global Nitrogen Cycles Rock 190.00,0 0.002/year Organic N

The Global Nitrogen Cycles