Geology Reference
In-Depth Information
Table 2. Characteristics of filamentous organisms in soils and caves
Diameters
Morphologies/
structures
Cell wall
morphology
Cell wall biochemistry
Fungi
3-6 mm on average
1 mm (min)-
30 mm (max)
Strands: 0.02
2. 1mm
Hyphae with or
without septum,
more or less
ramified. Bundles
of differentiated
hyphae forming
linear organs,
fungal strands
Thick-walled (up to
1 mm) and
thin-walled
(100-200 nm)
hyphae
Two layers: a fibrillar
component with
chitin and b-glucans
and an amorphous
component with
glycoproteins specific
to taxonomic groups
Actinomycetes 0.5-1 mmin
average, max
2 mm in some
genus
Ramified mycelium,
sometimes
fragmented
Wall 20-80 nm
thick
Gram positives bacteria
with one
homogenous layer of
peptidoglycan
(murein). Four types
of peptidoglycans
depending on genus
Fine roots
,2-0.2 mm
Single conducting
vessel 10-30 mm
Ramified structure
composed, at a
micromorphological
level, of complex
arrangements of
linear vessels
Highly variable in
thickness, from
0.1 mm in young
cells to 100 mmin
mature cells
Primary wall: network
of fibrous cellulose
and hemicellulose
embedded in a matrix
of pectin.
Secondary wall: only in
mature cells, can
contain lignin
Note: Review of the different filamentous organisms in soils synthesising characteristics such as filament diameter and morphology and
their cell wall morphology and biochemistry. References from Jones 1970; Dix & Webster 1995; Paul & Clark 1996; Bouma et al. 2001;
Carlile et al. 2001; Pregitzer et al. 2002; Prescott et al. 2003; Coleman et al. 2004; Pessoni et al. 2005; Hishi 2007.
as 'extreme'. On the other hand, physicochemical
parameters tend to be buffered and constant
throughout the year (e.g. mild temperature normally
equals MAST (Mean Annual Surface Temperature)
and fairly high humidity). These extreme but con-
stant conditions allow the presence of underground
ecosystems, which may or may not be connected
to aboveground energy-sources (Jasinska et al.
1996; Sarbu et al. 1996). Prokaryotes and fungi
are the most common organisms that can be encoun-
tered in caves, and their link in speleothem for-
mation is often proposed and debated. Moonmilk
is a common speleothem mineral, and its biological
or physico-chemical origin has long been discussed.
Today most of the theories involve microbial
mediation in its formation, but the exact role that
microorganisms play, whether it is bacterial or
fungal, is still being discussed (Gradzinski et al.
1997; Northup & Lavoie 2001; Ca˜averas et al.
2006; Barton & Northup 2007). In caves, moonmilk
is more likely to be present in the vicinity of soils
(Gradzinski, pers. comm.). This increases the prob-
ability of cave access for roots and their fungal
associates, and consequently their involvement in
the genesis of moonmilk.
Fungal strands and hyphae ultrastructure
Fungal hyphae size
Single fungal hyphae diameter is highly variable,
depending on the taxonomic position, environ-
mental conditions, age, and function of hyphae.
Nevertheless, for functional hyphae, an average
diameter of 3-6 mm is found in the literature (Dix
& Webster 1995; Carlile et al. 2001). Non-
functional hyphae, such as those from the cortex
of fungal strands, can have a diameter of 1 mm,
with an inner diameter of ,0.5 mm.
Fungal strands
Basically, a fungal strand is a bundle of juxtaposed
linear hyphae. They are organs produced by fungi to
explore their environment and to translocate nutri-
ents from one place to another. They have the
ability to extend over long distances, that is up to
30 m. In addition, macromorphologically, they
exhibit a variable diameter, depending mostly on
their age and remoteness from nutrient sources.
This diameter ranges from a few mmupto4mm
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