WAR  of  the  MICROWORLDS  

How do I kill Thee?   Let me count the Ways!   (# 31)  click here for full list

Arthrobotrys oligospora: There are nearly eighty decribed species of Arthrobotrys.   The most common and best known of these carnivorous predatory  fungi is Arthrobotrys oligospora.  It was also the first species of the genus to be described.  This species produces three dimensional adhesive nets that capture nematodes by matching a lectin in the net with a carbohydrate in the cuticle of the nematode. See below for more info on L/C bonding.

Left:  Net trapping device of Arthrobotrys oligospora.  Right: Larval nematode captured by adhesive nets.

Above Left: The careful observer should find THREE nematodes captured in this micrograph.   Note the septate assimilative hyphae inside the bodies and significantly the assimilative hyphae are now empty of protoplasm.  It takes less than 24 hr for Arthrobotrys to completely fill the body of the nematode with assimilative hyphae and transport the nutrient elsewhere.   Also note that the cuticle of the nematode has not been broken down.  No chitinases!   Good idea?    Above right:  Rick Hurst's diagram for the cover of  "The Nematode Destroying Fungi".   Students: Note that although these fungi are now commonly referred to as 'nematophagous' I preferred to use 'nematode-destroying' in the title of my book (1977).  Why so?

It was shown experimentally  (Nordbring-Hertz and Mattiasson, 1979. Nature, 281: 477 ) that a lectin in the trapping device of Arthrobotrys formed a chemical bond with a specific sugar in the wall of the nematode. This bond is impossible to break. Although some nematodes, close to moulting, can rupture their epidermis and escape.

To demonstrate this bonding phenomenon, nets were induced by the Nordbring-Hertz group in a number of cultures of Arthrobotrys.  The nets were then washed individually with solutions of known sugars.  The sugar that saturated the available sites on the adhesive nets of Arthrobotrys was found to be n-acetyl-D-galactosamine and nematodes were not trapped in the cultures to which this sugar was added.   It was confirmed that this sugar was a component of the nematode's cuticle.