"Paul J. McAuley - Reef" - читать интересную книгу автора (Mcauley Paul J)

ragged perimeter in pulsing spurts. As it grew, it exfoliated microscopic particles.
Margaret’s viewpoint spiralled into a close-up of one of the exfoliations, a few cells
wrapped in nutrient storing strands.
Millions of these little packages floated through the vacuum. If one landed on a host
thallus, it injected its genetic payload into the host cells. The view dropped inside one
such cell. A complex of carbohydrate and protein strands webbed the interior like
intricately packed spider webs. Part of the striated cell wall drew apart and a packet of
DNA coated in hydrated globulins and enzymes burst inward. The packet contained
the genomes of both the parasite and its previous victim. It latched onto protein
strands and crept along on ratchetting microtubule claws until it fused with the cell’s
own circlet of DNA.
The parasite possessed an enzyme that snipped strands of genetic material at
random lengths. These recombined, forming chimeric cells that contained genetic
information from both sets of victims, with the predator species’ genome embedded
among the native genes like an interpenetrating text.
The process repeated itself in flurries of coiling and uncoiling DNA strands as the
chimeric cells replicated. It was a crude, random process. Most contained incomplete or
noncomplementary copies of the genomes and were unable to function, or contained so
many copies that transcription was halting and imperfect. But a few out of every
thousand were viable, and a small percentage of those were more vigorous than either
of their parents. They grew from a few cells to a patch, and finally overgrew the
parental matrix in which they were embedded. There were pictures that showed every
stage of this transformation in a laboratory experiment.
“This is why I have not shared the information until now,” Opie Kindred said, as the
pictures faded around him. “I had to ensure by experimental testing that my theory
was correct. Because the procedure is so inefficient we had to screen thousands of
chimeras until we obtained a strain that overgrew its parent.”
“A very odd and extreme form of reproduction,” Arn said. “The parent dies so that
the child might live.”
Opie Kindred smiled. “It is more interesting than you might suppose.”
The next sequence showed the same colony, now clearly infected by the parasitic
species—leprous black spots mottled its pinkish surface. Again time speeded up. The
spots grew larger, merged, shed a cloud of exfoliations.
“Once the chimera overgrows its parent,” Opie Kindred said, “the genes of the
parasite, which have been reproduced in every cell of the thallus, are activated. The
host cells are transformed. It is rather like an RNA virus, except that the virus does
not merely subvert the protein and RNA making machinery of its host cell. It takes
over the cell itself. Now the cycle is completed, and the parasite sheds exfoliations that
will in turn infect new hosts.
“Here is the motor of evolution. In some of the infected hosts, the parasitic genome is
prevented from expression, and the host becomes resistant to infection. It is a
variation of the Red Queen’s race. There is an evolutionary pressure upon the
parasite to evolve new infective forms, and then for the hosts to resist them, and so on.
Meanwhile, the host species benefit from new genetic combinations that by selection
incrementally improve growth. The process is random but continuous, and takes place
on a vast scale. I estimate that millions of recombinant cells are produced each hour,
although perhaps only one in ten million are viable, and of those only one in a million
are significantly more efficient at growth than their parents. But this is more than
sufficient to explain the diversity we have mapped in the reef.”
Arn said, “How long have you known this, Opie?”