What microbes need

In your book, Our Wondrous World (Chapter 3), Disha notices something strange. She had left a slice of bread on the balcony for a cat, but the cat did not come for two days. Now the bread has coloured patches on it. But the pickles her Paati (grandmother, in Tamil) made two months ago are still delicious, because they are covered with oil! Why does some food spoil fast and some last a long time?

Disha asks her Anna what microbes need to grow. He tells her: microbes need moisture (a little wetness), air and the right temperature. If we take away any one of these, we can stop them in their tracks.

So the bread spoiled fast: it was left out in the air, with the moisture in it, and nothing to stop the microbes. The pickle lasted for months: the oil covering it kept the air out, so the microbes could not grow.