It is estimated that there are 10**30 (that is a 1 followed by 30 zeros) microbes on the earth. Each one is about 1 / 1,000,000 meters long. If we put them side by side they would stretch for 10**24 meters. the average galaxy is 10**21 meters in length so the microbe line would span about 6 galaxies!

(The Great Courses – Life in our Universe)