untitled

of Chaetomiumand Thermomycesresulted in a 2700 mg
weight loss.
The interpretation of even simple experiments like
these is difficult, but a number of points can be made:

• The losses in dry weight of the flask contents
  actually underestimate the amount of cellulose
  degraded, because some of the breakdown products
  of cellulose are converted into fungal biomass
  (which remains in the flasks).


• Thermomyces grew well in association with
  Chaetomium. It was seen to grow over the filter
  paper and produced its characteristic spores. So, in
  some way Thermomycesmust have obtained both a
  carbon source (sugars) and a nitrogen source from the
  association. Yet there was no evidence of parasitism,
  and this was confirmed by study of hyphal inter-
  actions on agar.


• Thermomycesin some way enhanced the breakdown
  of cellulose by Chaetomium. This might be expected
  from knowledge of the regulation of cellulase
  enzymes (Chapter 6), because any sugars that accu-
  mulate would slow the rate of enzyme action and also

repress the synthesis of further cellulases. So, by

using some of these sugars Thermomycesmight have

relieved this negative feedback.

• Thermomycesmust also have influenced the efficiency
  of nitrogen usage so that nitrogen was available to
  maintain the rate of cellulose breakdown for longer
  than when Chaetomium was growing alone. We
  saw in Chapter 11 thatChaetomiumsoon becomes
  nitrogen-limited, presumably because it cannot
  recycle nitrogen efficiently.

It would be interesting to know if Chaetomiumbenefits

in some way from the interaction, perhaps by increas-

ing its own biomass or by staving off its replacement

by other fungi in composts. However, there is no evid-

ence on this point, so this example must be described

as one of commensalism. At the least, this example

shows that fungi do not always have negative impacts

on one another.

Online resources

Database of Microbial Biopesticides (DMB). http://

http://www.ippc.orst.edu/biocontrol/biopesticides/

Weeden, C.R., Shelton, A.M., Li, Y. & Hoffman, M.P.,

eds. Biological Control: a guide to natural enemies

in North America. Cornell University. http://

http://www.nysaes.cornell.edu/ent/biocontrol/

General texts

Cook, R.J. & Baker, K.F. (1983) The Nature and Practice of

Biological Control of Plant Pathogens. American Phyto-

pathological Society, St Paul, Minnesota.

Deacon, J.W. (1983)Microbial Control of Plant Pests and

Diseases. Van Nostrand Reinhold, Wokingham.

Gnanamanickam, S.S., ed. (2002) Biological Control of Crop

Diseases. Marcel Dekker, New York.

Cited references

Chin-A-Woeng, T.F.C., Bloemberg, G.V. & Lugtenberg,

B.J.J. (2003) Phenazines and their role in biocontrol by

Pseudomonasbacteria. New Phytologist 157 , 503 – 523.

Deacon, J.W. (1973) Factors affecting occurrence of the

Ophioboluspatch disease of turf and its control by

Phialophora radicicola. Plant Pathology 22 , 149–155.

[Note: Ophiobolusis now called Gaeumannomyces;P.

radicicolais now called P. graminicola.]

Deacon, J.W. (1985) Decomposition of filter paper cellu-

lose by thermophilic fungi acting singly, in combination,

and in sequence. Transactions of the British Mycological

Society 85 , 663– 669.

Deacon, J.W., Laing, S.A.K. & Berry, L.A. (1991) Pythium

mycoparasiticumsp. nov., an aggressive mycoparasite

from British soils. Mycotaxon 62 , 1– 8.

254 CHAPTER 12

Fig. 12.19Weight losses of filter paper (originally 7 g dry
weight) in flasks inoculated with Chaetomium thermophile
alone (Ct) or C. thermophilewith the noncellulolytic fun-
gus Thermomyces lanuginosus(Ct+Tl) and incubated at
45°C. Mineral nutrients were supplied in the flasks with
either a standard amount of nitrogen (C : N ratio 174 : 1)
or double nitrogen (C : N ratio 88 : 1). (Data from Deacon
1985.)