Geology Reference
In-Depth Information
types of spirochetes which cluster on its outer surface in vast undulating hordes, some-
how orchestrating their individual movements so beautifully that the whole ensemble
glides gracefully around in search of tiny splinters of wood.
Figure 37:
Mixotricha paradoxa
, a wood-eating protist, swims only when the fuzz of its more
than 200,000 motility structures undulate. These are hypothesized to have evolved from symbiot-
ic treponema spirochetes. (
photo © Dean Soulia, courtesy Lynn Margulis
)
Lynn Margulis has vigorously promoted the idea that when the Archean eon was draw-
ing to a close, bacteria were trying out another kind of association, in which some of
them lived inside other bacterial cells. This endosymbiosis, or 'symbiosis from the in-
side', may have begun as a predatory relationship which turned friendly once the pred-
ator discovered that cooperation suited it much better than naked aggression. The pred-
ators resembled the modern-day
Bdellovibrio
, a veritable tiger of the bacterial world
which breaks its way into its victim, digesting it from inside using its high powered
oxygen-breathing metabolism to produce vast numbers of freshly minted offspring that
go off into the world as fierce hunters in their own right. But at some point some of
these predators must have taken pause once they found themselves in the safe, nutrient-
rich insides of their prey. Why go through all the bother of hunting down and devouring
one kill after another, when it would be far more sensible to rein in the aggression and
stay in this one nice host, feasting gently on its rich mix of food molecules whilst of-
fering the host a useful service in exchange? And the service? Nothing less than the use
