Activity profiling of ectomycorrhiza communities in two forest soils using multiple enzymatic tests

Abstract

Summary• Data on the diversity and distribution of enzyme activities in native ectomycorrhizal (ECM) communities are inadequate.• A microplate multiple enzymatic test was developed which makes it possible to measure eight enzyme activities on 14 individual, excised ECM root tips. Hydrolytic and oxidative enzymes are involved in the decomposition of lignocellulose, chitin and phosphorus-containing organic compounds. This test system was used to describe the functional diversity of ECM communities in two forest sites.• This set of tests proved to be accurate and sensitive enough to reveal a high diversity of activity profiles, depending on the fungal symbiont and the soil horizon. Ectomycorrhizas can be classified into specialists and generalists, and appear to complement each other in the same horizon to collectively perform all eight activities studied.• By including a higher number of different assays for more detailed analyses, ECM activity profiling will provide a valuable tool for studying the functional diversity of ECM communities.

Secreted enzymatic activities of ectomycorrhizal fungi as a case study of functional diversity and functional redundancy

“…Experimental site of Champenoux Fourteen ECM tips of each morphotype (chosen among the most turgid and healthy-looking ones, from a pooled sample of those of the six soil cores in which this ECM type was present) were used to determine their potential enzymatic activities, using the high-throughput photometric and fluorimetric microplate assays described by Pritsch et al (2004) and Courty et al (2005), and applied in previous studies (Buée et al 2007). Each well of the 96-well micro-titration plate contained a single ECM tip.…”

“…Activities of extracellular enzymes can be considered as functional traits to study functional diversity and resilience of ectomycorrhizal community (Cullings and Courty 2009). The first applications of this novel approach (e.g., Courty et al 2005Courty et al , 2007Buée et al 2007;Rineau and Garbaye 2009b;Jones et al 2010) have revealed that the activity profile of ECMs formed by the same species may change significantly according to everchanging ecological conditions (i.e., seasons, short-term climatic events, tree phenology, accidental or man-made disturbances such as soil amendment).…”

“…The recent development of new methods for determining the potential enzymatic activity profiles of individual ECMs makes possible to decipher trait diversity of ECM communities (Courty et al 2005). Activities of extracellular enzymes can be considered as functional traits to study functional diversity and resilience of ectomycorrhizal community (Cullings and Courty 2009).…”

Diversity in phosphorus mobilisation and uptake in ectomycorrhizal fungi

“…Depending on their substrate, the enzymes can be phosphomonoesterases or phosphodiesterases. Most of the studies addressing the release of phosphatases use artificial phosphomonesters such as p-nitrophenyl phosphate (pNPP) based on the procedure described in Tabatabai and Bremner (1969) or the fluorescent assay based on the release of 4-methylumbelliferone from 4-methylumbelliferonephosphate (MUP; Courty et al 2005Courty et al , 2006Pritsch et al 2004;Pritsch and Garbaye 2011) to estimate phosphomonoesterase activity.…”

“…However, so far, most of the ECM fungi showed maximal activities of released or surfacebound phosphomonoesterase at acidic pH when assayed with pNPP (Tibbett 2002) or with MUP (Courty et al 2005). ALP was measured in cell extracts of Cenococcum graniforme (renamed Cenococcum geophilum), and although the enzyme showed a high association with cell wall material, it was not released into the external medium from young fungal cultures (Bae and Barton 1989).…”