Patterns of organic acids exuded by pioneering fungi from a glacier forefield are affected by carbohydrate sources

Abstract

Bare soils in the area of retreating glaciers are ideal environments to study the role of microorganisms in the early soil formation and in processes of mineral weathering. The aim of our study was to investigate whether the source of carbohydrate would influence the patterns of organic acids exuded by fungal species. Three pioneering fungus species, isolated from fine granitic sediments in front of the Damma glacier from the central Swiss Alps, have previously been found to have the capability to exude organic acids and dissolve granite powder. In batch experiments, various carbohydrates, including glucose, cellulose, pectin, pollen, and cell remnants of cyanobacteria, fungi, and algae, were applied as carbohydrate sources and the patterns of exuded organic acids recorded. The results showed that two fungi, the zygomycete fungus Mucor hiemalis and the ascomycete fungus Penicillium chrysogenum, released a significantly higher amount of organic acids in dependence on specific carbohydrate sources. Pollen and algae as carbohydrate sources triggered significantly the exudation of malate in M. hiemalis, and pollen and cellulose that of oxalate in P. chrysogenum. We conclude that the occurrence of complex carbohydrate sources in nutrient-deficient deglaciated soils may positively influence the exudation of organic acids of fungi. In particular, pollen and remnants of other microorganisms can trigger the exudation of organic acids of fungi in order to promote the weathering of minerals and to make nutrients available that would otherwise be trapped in that cryospheric environment.

Microbial communities and primary succession in high altitude mountain environments

“…A follow-up batch of experiments showed a different pattern of organic acid release dependent on various carbohydrate sources in the same study area, including glucose, cellulose, pectin, pollen, and cell remnants of cyanobacteria, fungi, and algae (Brunner et al 2014).…”

C:N:P stoichiometry in six distinct habitats of a glacier terminus in the source area of the Yangtze River

“…Microorganisms, including bacteria, algae, fungi, and lichens, form complex communities and play important roles in initial biogeochemical processes and soil development (Kastovska et al, 2005;Zumsteg et al, 2012;Pushkareva et al, 2016). For example, microbial excreted organic acids can mine phosphorus from glacial till (Brunner et al, 2014). Because of absent (or low) vegetation coverage, the mined phosphorus will runoff easily, leading to decreased P from BaS to DS.…”