Hours later, Tucker found himself visiting Bukolov in a private room. The doctor had his own unique needs that went beyond food and medicine. He had borrowed a dissecting microscope and some lab equipment from a group of scientists doing research locally. Though he and the others were due to depart for the United States at midnight, Bukolov had wanted to get a jump on his investigation into a potential kill switch for LUCA.
Tucker didn’t blame him. After his brief encounter with General Kharzin, he knew they dared not waste a moment. He knew Kharzin would be working just as quickly to weaponize his prize.
“How are things going?” he asked Bukolov.
The man sat hunched over the dissecting microscope. A specimen of LUCA, sliced in half, lay on the tray under the lenses. “Come see this.”
Bukolov scooted back to make room for Tucker to use the eyepiece.
He found himself staring at the edge of the specimen. The outer surfaces were peeling away like the layers of an onion, the tissue pinpricked with tiny holes.
“That is a sample of dying LUCA taken from the cave,” Bukolov said.
Tucker pictured that glowing primordial garden.
“I’m fairly certain what you’re looking at here is a chemical burn, something given off by the lichen. What that chemical is I do not know, but I have a hypothesis, which I’ll get to in a moment. But first let me tell you about this mysterious glowing lichen.” Bukolov looked at him. “Are you familiar with lichens?”
“Considering I thought it was moss . . .”
“Oh, my dear boy, no. Lichens are much more ancient and strange. They’re actually made up of two organisms living in a symbiotic relationship. One is a fungus. The other is something that photosynthesizes.”
“Like plants.”
“Yes, but in the case of lichens, it’s either an algae or cyanobacteria that pairs up with the fungus.” He slid over a petri dish of the glowing organism. “In this particular case, it’s a cyanobacteria. Cyanobacteria are three to four billion years old, same as LUCA. Both inhabitants of the strange and hostile Archean eon. And likely competitors for the meager resources of that time.”
“Competitors?”
Bukolov slid the lichen sample and slices of bulbs resting in another petri dish next to each other. “You see, during that Archean eon, true land plants were yet to come. These two were the earliest precursors.”
He tapped the lichen. “Cyanobacteria gave rise to modern chloroplasts—the engines of photosynthesis—found in today’s plants.”
He shifted the sample of LUCA. “And here we have the earlier common ancestor, the stem cells of the flora world, if you will.”
Tucker pictured the microcosm of that ancient world found in the cave. “And the two were in competition?”
“Most definitely. In that harsh primordial time, it was a winner-takes-all world. And I believe it was that war that was the evolutionary drive for the rise of today’s modern plants.”
“And what we saw in the cave?”
“A snapshot of that ancient battle. But as in all wars, often common ground is found, cooperation necessary for short periods of time. What we witnessed below was an uneasy détente, two enemies helping each other survive in such strict isolation. Both needed the other to live.”
“Why do you think that?”
“During my studies here, I found healthy LUCA bulbs with dead lichen melting deep inside, being consumed. I believe living lichen can kill LUCA and use it as some fertilizer source. While at the same time, as the lichen die and flake from the roof and walls, it feeds the LUCA below, raining down, landing on those broad mushroomlike growths.”
“You’re saying they were feeding off each other.”
“That. And I’m sure the constant flow of water through the chamber brought a thin and steady flow of nutrients and biomatter to them as well. I also think their relationship was more nuanced, that they helped each other out in other ways. Perhaps the lichen’s bioluminescence served some beneficial advantage to the LUCA, while the sulfur-rich gas—that stink we smelled down there—given off by the germinating bulbs helped the lichen in some manner. I don’t know if we’ll ever understand it fully. That unique relationship was formed as much by geology as it was biology.”
“And how does that help us find the kill switch?”
Bukolov held up a finger. “First, we know that the living lichen can kill LUCA, but not dead lichen. So that knowledge alone will help me narrow my search for the chemical kill switch.”
He raised a second finger. “Two, we know who won that ancient battle. LUCA was vanquished, all but this small isolated garden, leaving behind only its genetic legacy in the form of modern plants. But cyanobacteria survive today, going by their more common name: blue-green algae. Because of their versatility, you can find cyanobacteria in every aquatic and terrestrial location on the planet, from the coldest tundra to the hottest volcanic vent, from freshwater ponds to sun-blasted desert rock. They are masters of disguise, merging with other organisms, like with the lichen here, but also with other plants, sponges, and bacteria. They can even be found growing in the fur of sloths.”
“It almost sounds like your description of LUCA from before. An organism with limitless potential.”
“Exactly!” Bukolov stared over at Tucker. “That’s because cyanobacteria are the closest living organisms to LUCA today. But from my studies—on a purely genetic scale—LUCA is a thousandfold more efficient, aggressive, and tough. Released today, unchecked and untamed, LUCA would wreak untold ecological havoc across every terrain on Earth, both land and sea.”
“But, Doc, it was defeated in the past. Like you said, it didn’t survive.”
“And that’s the second clue to discovering the kill switch: Why didn’t LUCA survive, while cyanobacteria did?”
Tucker had to say he was impressed with how much Doctor Bukolov had learned in such a short time. He could only imagine what he could accomplish with Sigma’s laboratory resources in the States.
“I have much to ponder,” Bukolov said.
Tucker’s satellite phone buzzed in his pocket. “Then I’ll leave you to it.”
He headed out of the room and answered the call.
“How are you all doing out there?” Harper asked as the line connected. He had already debriefed her about the past day’s successes and failures. “Will you be ready to go at midnight?”