Journal of Geophysical Research: Biogeosciences
© 2014 American Geophysical Union
Impact Factor: 3.44
ISI Journal Citation Reports © Ranking: 2013: 24/173 (Geosciences Multidisciplinary)
Online ISSN: 2169-8961
Associated Title(s): Journal of Geophysical Research
Scientists observe fungi dissolving minerals
They live in moist dark recesses and never see daylight. But these ectomycorrhizal fungi (EMF), which cling to the roots of trees in boreal forests, break down soil minerals and supply essential elements and nutrients to the trees. Along the way, they play a distinct, but not yet well-understood, role in bioweathering, a process in which water, air, and organisms interact to break down soil minerals within the first few meters of Earth's surface. In a synthetically designed and controlled laboratory environment, Gazz� et al. (2012) cultured EMF; they monitored the process as the fungi colonized a soil mineral on a petri dish over a period of 7 months. The authors then extracted individual grains of chlorite, a common soil-forming clay mineral, and cleaned the mineral surfaces to look at how the fungi had affected the mineral surfaces they came in contact with. Using atomic force microscopy, a specialized instrument that allows one to observe three-dimensional features at nanometer (10-9 m) scales, the authors found numerous primary channels, of the order of a micron (10-6 m) in width and up to 50 nm in depth, from which smaller secondary channels extended outwards; the network of channels resembled a herringbone-like pattern-evidence of dissolution by EMF. On the basis of these nanoscale observations, made for the first time on mineral surfaces altered by fungi in a laboratory, the authors concluded that their study provided observational evidence supporting the notion that EMF promote dissolution of soil minerals, a critical step in the process of bioerosion.