Water availability and temperature rule microbial extracellular enzyme activity in soils

Abstract

This work analyzes the effect of temperature and water availability on microbial extracellular enzyme activity in soils from different perspectives. First, we have develop a new method that allows the study of soil extracellular enzyme activity at different temperatures and water activities. The behavior showed by different culture microorganisms (thermophiles and mesophiles) is different according to water activity, we have provided data of thermophilic responses to water activity never reported before where maximal enzyme activity have been showed at low water availability. Second, the analysis of environmental conditions that apparently lead adaptation processes in soil microorganisms that make release high temperature and desiccation performing enzymes that provides of nutrient source when soils are hot and dry. Additionally, we have give indices of environmental variables (climate and soil composition) which apparently rule the adaptation processes for soil microorganisms. Third, we have analyzed the effects of temperature and water content in a barely studied feature of soils extracellular enzymes, the capability to persist in soil during long periods of time and accumulate. Our finding suggest that high-temperature extracellular enzymes could be naturally accumulated in soils proportionally longer than enzymes from mesophiles. and remarks water content as a crucial factor controling the capability of extracellular enzymes to remain active in soils. Fourth, the knowledge generated in the study of the water activity and temperature have been relevant for the application to biodegradation of halogenated pollutants under desiccation and high temperature circumstances. We have found that thermophiles can perform dehalogenation under high temperature and low water activity. The thesis presented here contributes to understand extracellular enzyme activity in soils at high temperature and low desiccation, this is truly relevant for the understanding of atmosphere-soil carbon dynamics, specially in a framework of climate warming where soils will experience more frequent high temperature and desiccation events.