Evolutionary Endosymbiosis: A Match Made in Heaven
By Agnes Ann Nogal
Department of Biological Sciences
University at Buffalo, State University of New York

In the beginning, there was nothing. Nothing exploded into everything. Welcome to the Big Bang and the beginnings of the primordial ooze.

Then came along Sam, quite behind the algae that had been on Earth for a while after they developed from the primordial ooze. Sam was your typical, run of the mill, large anaerobic bacterium, who wandered the early Earth, puttering along with a fairly small supply of ATP. There was oxygen in the atmosphere, at least some, but Sam didn't have the ability to use that oxygen to help him out in the least.
Now Sam was good friends with a runty little aerobic bacterium named Oscar. Oscar zoomed around the Earth, full of energy, so happy to be able to use the oxygen supply to enhance what he was able to do.

"Hey Oscar!" Sam said to Oscar one fine day. "Why are you looking so down and sad today? Is something the matter? I don't remember ever seeing you unhappy before."
"Hi Sam," Oscar panted. "I'm just not feeling myself today. I'm full of energy, but there's something in the air that's making me not be able to use it quite right. I'm too little to try to find another place to live. I guess I'm stuck being unhappy now."
This conversation with Oscar made Sam very sad afterward. He wondered if there would be anything at all that he would be able to do for Oscar, to make him happy and full of energy. "Then again," he thought to himself, "I'm not the one who's ever full of energy to do much more than sit around and live."

Later that same day, Sam was in his favorite part of the rock on which he lived, when he met two of his acquaintances from under the rock. Harry was like Sam, the run of the mill, big anaerobic bacterium that couldn't really move too far from his home. Jim was like Oscar, the energetic happy aerobe, but recently, just like Oscar, Jim had been really sad. There was something different about them, but Sam couldn't place his finger on it. Then something struck him. Sam was on the very top of the rock, but Harry and Jim were from underneath the rock. He only knew them from talking to them into the night, shouting through the air.
"I wonder how Harry and Jim made it on to the top of the rock, without running out of energy?" he pondered to himself as he went to greet his acquaintances.

"Hey Harry and Jim," he shouted as he tried to figure out what seemed not quite right with the two of them. "What brings you to my side of the rock?" "Hey Sammy my good boy!" Jim yelled and grinned back. "Top of the morning to you! Great morning isn't it? Hey did you see that commotion in the swamp yesterday? Wowee. That was something. So how is everything going? Still sitting in that same place on the rock? Why don't you move around? See some more of the rock!"
Sam was a little confused at this point. Just the other day, Jim had been moping around, cranky and just very listless. Today, Jim was back to his energetic and extremely chipper self.
"Gee, I wonder what happened that changed him," Sam thought as he struggled to see Harry and Jim as they approached him. Something was still nagging him at the back of his mind.
"Hey Sam," Harry cried. "I feel great today. It's a wonderful day. I have SO much more energy than I ever did before."
"Uh, hey guys," said a very confused Sam to the both of them. "What happened to you two? You've changed so much!" At that moment, the two bacteria were close enough for Sam to see what had changed with them. "Oohh!" Sam gasped, rather flabbergasted upon seeing Jim talking from the inside of Harry.
"Oh yeah, we didn't tell you about our arrangement?" Harry grinned as he poked into himself to poke at Jim. "Yeah, we were both not doing well; I tell you, the air's changing. So we decided to have a mutual relationship with one another. You know, I help him survive as things are changing, and bring Jim close to better food supplies, and I get more energy to do everything from Jim. I say, I really do love the new way of using oxygen to make energy. It saves so much time by giving more energy for less food." "You can do that?!?" Sam said and stared in amazement. "But doesn't Jim get digested by you Harry?"
"Oh, no, Jim's way too small to be able to be digested. My cell likes to eat the big things, and doesn't care at all for little tiny things like Jim," Harry laughed.
"Huh," Sam said, still not knowing how to react. His mind was racing a million miles a minute, and then the light bulb came on. If this were working so well for Harry and Jim that they were able to travel from underneath the rock all the way to the top of the rock, well, then maybe it would work for both him and Oscar. They were best friends, and a little more intimacy didn't mean too much. Sam, at that moment, made up his mind to approach Oscar and offer this idea up to Oscar. It just could work. "Sorry guys," Sam said abruptly. "I need to go find Oscar."

Sam hurried off to find Oscar, hoping that Oscar would take to the idea. He found Oscar sitting languidly by a rather wet patch on the rock.
"Hey Oscar, I have a proposal for you," Sam panted as he hurriedly slid towards Oscar.
"What is it?" Oscar asked crossly.
Sam explained the situation between Harry and Jim patiently and thoroughly to Oscar, answering Oscar's questions as best as he could. Behind his back, he formed a pseudopodium structure and gave it fingers, then crossed those fingers in hopes of Oscar accepting the proposal.
"Know what, Sam?" Oscar said decidedly. "I'll do it. I really have nothing to lose right now. I'd probably die if I didn't go into symbiosis with you, so why not try it? When do you want to do it? Right now?"
"Well, okay! I wasn't planning to do it right this second, but if you want to, I'll do it," Sam said excitedly and jumped around a bit. Then he calmed down and became rather serious. Oscar came really close to Sam, and pressed his cell into him. In turn, Sam's cell membrane caved inward and started to envelop Oscar, continuing until Oscar was enveloped totally by his own cell membrane, and then pushed Oscar further inside of himself.
Oscar opened his eyes and looked around.
"Hey! I'm actually inside and safe. Yay!" Oscar exclaimed.
"Hmmmm, I was thinking Oscar, do you want to pass me some of your DNA along, so that both your offspring and mine will be together like this? That way, neither offspring will have to go through individual hardships like we did," Sam said carefully.
"You know, that's a good idea," Oscar said as he slipped some of his DNA into Sam's cytoplasm.
'I'll never be able to live without you anymore Oscar," Sam said soberly. "Never will I without you," Oscar responded.

So it happened that the relationship between Sam and Oscar benefited both of them greatly and they agreed that they had done the right thing in the end.
Soon after their combination, they each produced a son, but Oscar's son was inside of Sam's, just as they had wanted it to happen. They decided to name both of their sons Johnny, just because they didn't seem like separate entities anymore.
Johnny grew and thrived, and of course, he became the typical adolescent rebel offspring, running with the tougher crowds. Same and Oscar worried, but there wasn't anything they could do. He was his own person.

One day, Johnny returned from having been gone for several days, disappeared without a trace. Johnny approached slowly, as if he was afraid of something.
"Hey dads, guess what?" he shouted to Oscar and Sam. "I tried something new. I won't be able to live with you guys anymore."
Worried, Sam and Oscar looked at their son to figure out what he had done to himself. They spotted something green inside, next to Oscar's "son."
"Sam, Oscar, meet Jared. He's a part of me now. See the green in him? That means he makes his own food, and food for me to use. I don't have to search for food with you guys anymore!"
Sam and Oscar looked at each other and sighed. They both knew that this was something completely different than they had ever known, but they couldn't say it was bad for Johnny, not at all. He had grown into his own being.