untitled

would need to be supplied with these by the photo-
synthetic partner. This astonishing newly discovered
type of symbiosisshould spur renewed interest in the
study of rudimentary associations among the micro-
scopic organisms in soil.

Fungus–insect mutualisms

Several insects have developed mutualistic associations
with fungi, to provide the insect with a suitable food

source. The likely driving force for this is the inability

of insects (or other animals) to degrade cellulose.

Instead, the insect has to harness the cellulolytic

activities of fungi to obtain food. In the more highly

evolved associations of this type, the insect ensures the

perpetuation of the mutualism by:

• carrying and transmitting the fungus in specially
  adapted organs, called mycangia;


• inoculating a suitable substrate with spores of the
  fungus;

276 CHAPTER 13

Nostoc

heterocyst

symbiosome

membrane

plasma

membrane

cell wall

lipid droplet

hypha

vacuole

V

V

V

SM

CW

PM

N NC

M

BLO

(a) (b)

Fig. 13.25Drawings of the Geosiphonbladder compartmentation. (a) Cells of Nostocare located in membrane-bound
symbiosomes towards the periphery of the fungal cell. (b) Detail showing a bacteria-like organism (BLO), cell wall (CW),
mitochondrion (M), nucleus (N), Nostoccell (NC), plasma membrane (PM), symbiosome membrane (SM), and vacuole
(V). (Image courtesy of A. Scheussler & M. Kluge; from Schuessler & Kluge 2001.)