Carbon Use Efficiency:

Transcription

1 CAU Beijing Carbon Use Efficiency: Concept for an Universal Approach to understand Microbial Life in Soil Yakov Kuzyakov & Paul Dijkstra C U E What we think? What we measure? What is ongoing? Time! RUDN University Moscow North Arizona University Think Measure Ongoing Lecture materials: wwwuser.gwdg.de/~kuzyakov/china Download PDF of papers: wwwuser.gwdg.de/~kuzyakov/papers.htm Definitions Carbon use efficiency (): the efficiency with which C taken up by the microbial community is converted into microbial biomass C (Winzler & Baumberger 938; Clifton 946) <.0 Growth yield efficiency: The proportion of substrate that is assimilated into the biomass alone, except which no microbial growth occurs (Thiet et al. 2006) < Ecological efficiency: The efficiency with which energy is transferred from one trophic level to the next. ~ 0% Substrate use efficiency: the amount of produced biomass per unit of added substrate >.0 >.. 3 CH 2 O : What We Think ATP + NADH T i m e Metabolisms Anabolism Catabolism CO 2 = 0 = 0.65 (0.9?) Necromass C sequestration 4

2 Classical Chemostat Y Chemostat Continuous substrate input Time irrelevant Growth (Y) Optimal conditions Temperature + moisture Nutrients + C, ph No stress One microbial species All cells are active and growing Soil Pulse events Time crucial Constant biomass: Steady state Microbes in soil are living in a world where everything is limiting (Burns et al. 200 SBB, CC-8) Only stress 0 0 species in g soil Active microorganisms: 0% Cultivable = 00% % No enemies / predators Enemies, predators, phages Well mixed No recycling Y: yield µ: growth rate CO 2 : respiration rate Spatially separated Very efficient recycling 5 Soil Organisms: How they uptake and utilize C? Microorganisms (Bacteria, Fungi, Archaea) Cannot intake non-soluble particles need solubilisation exoenzymes slow process only of soluble compounds not immediately diffusion to the cells 6 : What We Measure C, C, 8 O, 5 N C, C Steady state C or C incorporation 5 N immobilization ( 5 NH 4+ pool dilution) How we measure? 2 5 / 5 / 2 Red: the main uncertainty U n c e r t a i n t y Wang et al. 20 DOM Chloroform fumigation T i m e C, C, 8 O, 5 N 8 8 O incorporation in DNA / 8 / 2 PSL (Position Specific Labeling: C/ C) C MB? 7 9

3 .0 Measured C MB Start of Start of Metabolism C Input Metabolic PPP TCA G l u c o l y s I s B i o m a s s Time Dijkstra 20, 205 SBB How long? 2 Number of sites rate 3 h. T ½ of amino acids in soils Jones et al SBB Amino acids T ½ in soil (h) Time after the C input Sugars 2 h is not instant: Maximal is not possible Gunina & Kuzyakov 205 SBB.0 ~ 0.85 Measured 0.0 Metabolic : Theory for & Growth Shifts in metabolic pathways (dormant active) Energy spilling reactions Cell motility Changes in stored polymers Osmo- and ph regulation Extracellular losses of compounds Proofreading, synthesis and reparation of macromolecules: enzymes, RNA, lipids Defense against stress: O 2, salts, Time 2

4 Energy Costs for & Growth vs. Growth Chemostate Energy Growth Harder 997 FEMS 0 Growth rates: µ 5 Effect of specific growth rate (µ) on the % of C used as maintenance energy with 3 sugars Zafar et al Various Microorganisms vs. Growth Growth 30 Minimal error Measured Think Measure real Ongoing Measured Commonly measured Very low : T ½ = 300 days No growth only: T ½ = 30 days No growth 7 : T ½ = 30 days Growth = 20 x Not any of the options allow to get the real!

5 .0 ~ Measured 0.0 Metabolic Measured : Theory = f(time, Rate, Active/Dormant MO) only + Growth T i Timem e = Metabolic ( + Turnover) Time Dormant + Active Growth = 30 Active only 2 Active MO ~ 3% of total! Time rate BAT Biologically Active Time Is the rate of time constant? BAT depends on environmental conditions Microorganisms in soil are always in stress! Not optimal environmental conditions Temperature Moisture O 2 availability, e.g. paddy soils Changes of maintenance and growth depending on environmental conditions Utilization of slow substances BAT = 5 50 days / year Measured Duration Franko U 997 Temperature Q 0 = 2 = Metabolic ( + Turnover) BAT Moisture we measure Constant microbial biomass assume maintenance, but: Cycling С Death / Growth Cycling Death Growth Bacterial Death: Consequences Bacterial host Viruses Cell lysates Lysis + Death + Growth Number of cells Low Low CO 2 Low High Cell age Old Young Strategists K r Energy needs Low High Yield < 0 0 C/ C High Low 8 O/ 5 N Low High 22 normalized real C 60 N 6 P C 0. 6 N P C N 0.85 P Consequences Stoichiometry changes Inaccessibility in nano-pores (< µm) Spatial separation of survived cells from cell debris Losses of proteins and endoenzymes Kuzyakov & Mason-Jones SBB 208

6 Other Uncertainties for in Soil : Steps Sorption of organic C in soil Fumigation-Extraction procedure ( C, C) Recalculation of DNA to total MB ( 8 O) Stoichiometric limitations (e.g. high C/N, C/P, C/... Ratio) Exoenzymatic decomposition of non-soluble substances Geyer et al Ecosystem Community Population : Upscaling Geyer et al Is based or rates (not amounts, not stocks) is a theoretical value consisting on various components Cannot be measured directly: C, C, 8 O, 5 N,... only: dynamic measurements + simulation Measured Time is crucial Microbial time has not a constant rate our time BAT: Biologically Active Time We measure duration, not the biological time! Process rates and their ratios are the most unclear If uptake is slow measured 0 : & growth Absence of biomass increase maintenance Death + Growth Limitations for Conclusions: in Soil = Metabolic ( + Turnover) BAT levels: Popultion > Community > Ecosystem B i o l o g i c a l ly A c t i v e T i m e Thank you! 谢谢! 27