How do taumoeba get used to stop Astrophage in the story?

In Project Hail Mary, Ryland Grace and Rocky collaborate to breed taumoeba that are resistant to Astrophage. By combining their scientific knowledge, they develop these Astrophage-resistant taumoeba as a biological countermeasure. The taumoeba can then be used to control or stop the spread of Astrophage, which is draining the sun’s energy and threatening both Earth and Rocky’s home star system. This breeding of resistant taumoeba is a key part of their solution to save their worlds from the Astrophage crisis.