The Evolution Deceit Bacteria enter into mutually beneficial
relationships with plants as well. For example, bacteria with
nitrogen-binding properties live in the roots of clover and of
peas. Any plant deprived of nitrogen will die sooner or later.
For that reason, the bacteria living in nodules in the roots are
so important. Why do these bacteria prefer peas? The reason lies
in chemical communication among the two species. Symbiotic
bacteria encourage the formation of small nodules in the roots
by activating certain genes in the plant. The bacteria then use
these nodules as shelters. In return, the plants acquire an
endless supply of nitrogen. Nitrogen-fixing soil bacteria
(Rhizobium sp.) living on a root nodule of a bean plant 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, intest