Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Sentence1: gills are used for breathing water by aquatic animals. 
Sentence2: gills are used for breathing water by sharks.
are

Sentence1: bacteria can cause people to become ill. 
Sentence2: bacteria can cause people to die.
bacteria

Sentence1: Bacteria thrive in higher temperatures. 
Sentence2: Higher temperatures cause food to spoil.

higher