Page 78 - The Microworld Miracle

peas? The reason lies in chemical communication among the two
species. Symbiotic bacteria encourage the formation of small nod-
ules in the roots by activating certain genes in the plant. The bacte-
ria then use these nodules as shelters. In return, the plants acquire
an endless supply of nitrogen. 44
Another symbiotic relationship exists between the puffer fish
and intestinal bacteria. Porcupine fish possess an unusual poison

known as tetrodoxin, which is produced by the bacteria living in
the fish's intestines. Although the greater part of this toxin is found
in the liver, intestine and other internal organs, it spreads all
through the fish's flesh. Some of it even enters the muscles.
Anything that eats a porcupine fish is therefore
exposed to a grave danger. Predators aware
of this danger avoid eating it. 45 In turn,

this contribution from the bacteria pre-
vents them from falling prey to other
fish.

THE MICROWORLD MIRACLE The symbiotic
bacterium has
found shelter for
itself in bubbles
that emerge in
pea roots. In re-
turn, the plant
obtains a never-
ending store of

76 nitrogen.