Ecoenzymatic stoichiometry of microbial organic nutrient acquisition in soil and sediment

摘要

能量和养分通过生态系统的流动由代谢限制和rn养分供应两个因素决定。现在，对由微生物rn释放到环境中去消化有机质的外部"生态酶”rn(ecoenzymes)所做的一项研究表明。这些酶rn的活性遵从一个一致的比例关系，这种关系rn独立于微生物群落的组成。研究人员在土壤和rn淡水沉积物中对调控异养微生物群落大部分rn碳、氮和磷摄取的四种酶进行了测量，在所有rn这些生境中，碳、氦和磷的吸收活性比都接近rn1：1：1。生态酶活性可被看作是将两个主要生态rn理论(化学当量理论和代谢理论)统一起来的一rn种联系，因为酶的表达是由环境养分供应状态rn的随机性专门调控的细胞代谢的一个产物。%Biota can be described in terms of elemental composition, expressed as an atomic ratio of carbon:nitrogen:phosphorus (refs 1-3). The elemental stoichiometry of microoorganisms is fundamental for understanding the production dynamics and biogeochemical cycles of ecosystems because microbial biomass is the trophic base of detrital food webs. Here we show that heterotrophic microbial communities of diverse composition from terrestrial soils and freshwater sediments share a common functional stoichiometry in relation to organic nutrient acquisition. The activities of four enzymes that catalyse the hydrolysis of assimilable products from the principal environmental sources of C, N and P show similar scaling relationships over several orders of magnitude, with a mean ratio for C:N:P activities near 1:1:1 in all habitats. We suggest that these ecoenzymatic ratios reflect the equilibria between the elemental composition of microbial biomass and detrital organic matter and the efficiencies of microbial nutrient assimilation and growth. Because ecoenzymatic activities intersect the stoichiometric and metabolic theories of ecology, they provide a functional measure of the threshold at which control of community metabolism shifts from nutrient to energy flow.