and the bacteria living inside the sclerotia grains were not adapted to the low-pH soil
environment in which the sclerotia were found. These results suggest that some
bacteria in sclerotia grains may initially derive from endophytic bacteria of
ectomycorrhizal fungi that colonize the sclerotia. According to Nonoyama (2010),
clones of Dehalococcoides sp. and Desulfuromonas sp. have been detected in
sclerotia grains from forest soil. Planctomycetes and γ-proteobacteria, which are
not detected in the surrounding soil, were also detected inside these sclerotia.
Studying the bacterial community structure inside C. geophilum sclerotia, where
fungi and bacteria share a habitat, may improve our understanding of the strategical
interdependence between bacteria and fungi and the function of sclerotia for sustainable symbiosis between host plants and microorganism.
Returning to visible components of soil, study of the biological connections
between sclerotia, sclerotia-forming fungi, and fungivore arthropods present in
strongly acidic to extremely acidic forest soils revealed that Acari and Collembola
may play a major role in the regulation of ectomycorrhizal fungi in forest soils and
that fungivory of Acari and/or Collembola toward sclerotia-forming ectomycorrhizal
fungi plays a key role on regulating sclerotia formation in soil.
Sclerotia in soil offer many advantages for the study of mesoscale soil processes.
Because sclerotia are composed of 50% organic carbon by mass, the accelerator
mass spectrometry AMS
14 C age of individual grains (>2 mg) can be determined. In
strongly acidic forest soils, sclerotia are estimated to contain up to 1.0% of total soil
carbon. Sclerotia in forest soils are presumably produced annually, and thus the age
of sclerotia particles in the topsoil indicates the rate of turnover of sclerotia-form
carbon. Another advantage is its durable structure, which allows us to characterize
their material properties by various instrumental analyses. The spherical structure of
sclerotia grains would be altered by germination and hyphal elongation processes,
and chemically transformed via both labile and recalcitrant organic carbon pathways.
Deposition of perylene in lake sediments following the degradation of C. geophilum
sclerotia is an example of the latter pathway derived of Cg sclerotia grains (Itoh et al.
2010). Saccharides in soil is an example of the former pathway.
The elements enriched in sclerotium in neutral-alkaline forest soils are clearly
different from those in strongly acidic forest soils. Although these differences in
elemental dynamics may also be explained by differences in the environment
between cool-wet and semi-arid areas, the biochemical dynamics in soil–plant
interaction, and the biological intention of sclerotium formation by Cg in various
environment are unknown. We believe that certain metals in sclerotia grains are
abiotically enriched by absorption to sclerotia melanin, even after germination
activity has been lost. And because fungal sclerotium can remain in soil for long
periods, accumulating metal compounds, they may archive the mobilization and
availability of metal ions derived of soil pollutants or other toxic substances.
The melanic sclerotia in soil, formed by Cenococcum sp., are known to have the
widest global distribution, probably because of its broad taxonomy. Because fungal
melanin-pigment has a high capacity to adsorb metals (Mowll and Gadd 1984),
melanic sclerotia grains may have high uptake metal compounds, resulting in
formation of organic complexes. Investigating melanic sclerotia grains that bridge
12 Sclerotia Grain, a Mesoscale Component of Soil
211
environment in which the sclerotia were found. These results suggest that some
bacteria in sclerotia grains may initially derive from endophytic bacteria of
ectomycorrhizal fungi that colonize the sclerotia. According to Nonoyama (2010),
clones of Dehalococcoides sp. and Desulfuromonas sp. have been detected in
sclerotia grains from forest soil. Planctomycetes and γ-proteobacteria, which are
not detected in the surrounding soil, were also detected inside these sclerotia.
Studying the bacterial community structure inside C. geophilum sclerotia, where
fungi and bacteria share a habitat, may improve our understanding of the strategical
interdependence between bacteria and fungi and the function of sclerotia for sustainable symbiosis between host plants and microorganism.
Returning to visible components of soil, study of the biological connections
between sclerotia, sclerotia-forming fungi, and fungivore arthropods present in
strongly acidic to extremely acidic forest soils revealed that Acari and Collembola
may play a major role in the regulation of ectomycorrhizal fungi in forest soils and
that fungivory of Acari and/or Collembola toward sclerotia-forming ectomycorrhizal
fungi plays a key role on regulating sclerotia formation in soil.
Sclerotia in soil offer many advantages for the study of mesoscale soil processes.
Because sclerotia are composed of 50% organic carbon by mass, the accelerator
mass spectrometry AMS
14 C age of individual grains (>2 mg) can be determined. In
strongly acidic forest soils, sclerotia are estimated to contain up to 1.0% of total soil
carbon. Sclerotia in forest soils are presumably produced annually, and thus the age
of sclerotia particles in the topsoil indicates the rate of turnover of sclerotia-form
carbon. Another advantage is its durable structure, which allows us to characterize
their material properties by various instrumental analyses. The spherical structure of
sclerotia grains would be altered by germination and hyphal elongation processes,
and chemically transformed via both labile and recalcitrant organic carbon pathways.
Deposition of perylene in lake sediments following the degradation of C. geophilum
sclerotia is an example of the latter pathway derived of Cg sclerotia grains (Itoh et al.
2010). Saccharides in soil is an example of the former pathway.
The elements enriched in sclerotium in neutral-alkaline forest soils are clearly
different from those in strongly acidic forest soils. Although these differences in
elemental dynamics may also be explained by differences in the environment
between cool-wet and semi-arid areas, the biochemical dynamics in soil–plant
interaction, and the biological intention of sclerotium formation by Cg in various
environment are unknown. We believe that certain metals in sclerotia grains are
abiotically enriched by absorption to sclerotia melanin, even after germination
activity has been lost. And because fungal sclerotium can remain in soil for long
periods, accumulating metal compounds, they may archive the mobilization and
availability of metal ions derived of soil pollutants or other toxic substances.
The melanic sclerotia in soil, formed by Cenococcum sp., are known to have the
widest global distribution, probably because of its broad taxonomy. Because fungal
melanin-pigment has a high capacity to adsorb metals (Mowll and Gadd 1984),
melanic sclerotia grains may have high uptake metal compounds, resulting in
formation of organic complexes. Investigating melanic sclerotia grains that bridge
12 Sclerotia Grain, a Mesoscale Component of Soil
211