Lacto

Lacto taught the fermentation plainly, because it was proud of it.

"Fermentation is how I make energy without any air," Lacto said. "I take lactose, break it down, keep a little energy for myself, and the leftover is lactic acid — which spills out into the milk around me. That souring isn't a side effect. It's the whole gift twice over." It counted on small fingers. "First, the acid curdles the milk into yogurt, which keeps longer and is easier to digest — that's why people have made yogurt and cheese and pickles and sourdough with fermenting microbes for thousands of years, long before anyone knew we existed. Second, that same acid is how I protect. Most microbes that would spoil food or upset a gut can't stand a sour, acidic place. I make the neighborhood too tangy for them. I don't fight them off. I just make a home they can't move into."

The older students heard the subtext: you can keep a place safe by quietly shaping it, not only by battling for it.

Lacto had once thought helping had to look like fighting.

"When I was small I watched Guard patrol and strike, and I thought that's what protecting looked like," Lacto admitted. "I felt useless — I don't attack anything. All I do is sit in the gut and make a little acid and take up a little room." It laughed softly. "Then Myco showed me what happens to a gut when the helpful bacteria are gone — after a sickness, say. The harmful ones move right into the empty space and take over, because nothing is there crowding them out. That was when I understood. Every bit of room I fill is room a harmful microbe can't have. Every drop of acid I make is a door that won't open for them. I protect by being present. Presence is a kind of strength too."

A student asked whether a bacterium in your food was a gross thing, honestly.

"I understand why you'd think so — but no," Lacto said, unbothered. "Your gut is home to trillions of bacteria right now, most of them helping you — digesting food you couldn't break down alone, making vitamins, training Guard's system, holding the space. That whole community is your microbiome, and you feed part of it every time you eat yogurt or kefir or sauerkraut. The word bacterium isn't a synonym for dirty. Most of us are staff, not intruders." It patted the yogurt jar. "This isn't spoiled milk. It's milk with a helpful friend living in it — and when you eat it, the friend comes to stay a while, and helps in there the same way it helped in here."