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.

[Q]: Sentence1: Microbes are also called bacteria or microorganisms. 
Sentence2: Disease-causing bacteria have a negative impact on the body.
[A]: bacteria


[Q]: Sentence1: a polar bear requires a cold environment. 
Sentence2: polar bears live where there are fewer animals.
[A]: bear


[Q]: Sentence1: Viruses infect and live inside the cells of living organisms. 
Sentence2: An infection is an illness caused by the invasion of a virus or microorganism.
[A]:
infect